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C HAPTER Models ||

OBJECTIVES

After completing this chapter, you will be able to: ■ describe how are made through the addition of different of . ■ describe how colors are reproduced through the use of colored . ■ use Photoshop’s tools to measure and define colors using the RGB and CMYK color models. ■ describe the attributes and uses of each of the color models available in Photoshop. ■ define color and use Photoshop’s tools to determine if a color specified in one is out of the gamut of another model. ■ specify colors using the color models available in Photoshop. ■ convert from one color mode to another. ■ use the Multichannel mode to improve the conversion of a color into a image. ■ specify spot colors and CMYK simulations of spot colors. ■ specify attributes using both and CMYK. | 131 132 | C HAPTER THREE||

Color is a very important and dynamic part of graphic products. It adds interest and realism to documents, can be used to emphasize points in the text, sets a mood for the piece, and may cause or contribute to psychological reactions. ■ color model In its purest form, color is fairly easy to understand. However, when ■ RGB model humans get involved in reproducing or discussing color, many problems ■ CMYK model can and do arise. This chapter will introduce you to the phenomenon ■ L*a*b model called color and to some of the ways color can be viewed and discussed ■ HSB model using color models. A color model is a way of categorizing and describing the infinite variety of colors that are found in nature. Several color models ■ spot color are available in Photoshop, including RGB, CMYK, L*a*b, HSB, and a number of spot color systems. The RGB model uses , , and light to form colors and is widely used in , , and computer monitors. The CMYK model uses , , , and to reproduce photographs using processes. L*a*b is a very technical model used by computer programs, such as Photoshop, and color scientists to define and translate colors from one system to another. The L*a*b model defines colors in terms of and two color channels, “a” and “b.” The HSB model is used by artists to define color in terms of , saturation, and . Various spot color systems define colors based on preprinted samples of various colored inks. ■ high fidelity During this chapter, you will use several of these models to specify color colors. You can use the Color and the dialog boxes to define colors using any of Photoshop’s available color models. Several color models are not available in Photoshop, including the , the Ostwalt System, and the Foss Color Order System. In addition, Photoshop 4.0 does not support any of the high fidelity color models, such as the CCMMYYK or systems. High fidelity color reproductions extend the tonal range of printed photographs and are printed using six, seven, eight, or more colors of rather than the customary four (CMYK). You may see reference to these color models in other books because they are occasionally used in the printing and publishing industries. ■ color mode Photoshop uses several color modes to display, print, and store colors ■ created using various color models. Some color modes have the same names as color models, including the RGB, CMYK, and Lab modes. (The L*a*b model is called Lab mode in Photoshop.) When an image is saved by || Color Models | 133

Photoshop in RGB, CMYK, or Lab, a separate channel is created for each color required by the model. For example, an RGB image has three channels—red, green, and blue, while a CMYK image has four channels— cyan, magenta, yellow, and black. These channels can be displayed and manipulated either individually or in groups. Individual channels are accessed from the Channels of the Layers/Channels/Paths palette. Photoshop can also display, print, and store colors using the , Grayscale, Duotone, and modes. The choice of which color mode to use for an image depends on the final use of the on which you are working. For example, color photographs to be printed using conventional printing processes must be stored in the CMYK mode, while photographs to be printed in black-and- must be stored in the Grayscale mode. A Grayscale image may be converted to a Duotone if a special effect is desired. Images to be displayed only on computer screens are usually stored in the RGB mode. However, many multimedia programs require color images to be stored in the Indexed Color Mode. Bitmapped, Grayscale, Indexed Color, and Duotone images all consist of a single channel. The final color mode is Multichannel. If you convert an RGB, CMYK, or Lab image to Multichannel, each channel of the original image is converted to a separate grayscale channel. For example, if you convert a CMYK image to Multichannel, the image will be converted to four grayscale images. The Multichannel mode is also used for specialized purposes, such as converting a color image to a contrasty grayscale image, or converting a duotone for printing in the Scitex CT format.

Converting an Image from One Mode to Another

■ color You can convert an image in one mode to another mode. For example, separation you can convert an RGB image to Lab by choosing Lab Color from the Mode submenu of the Image . If you convert an image to the CMYK mode, the process is known as color separation. Color separation was once a difficult and time-consuming task. Now, however, it is accomplished by simply choosing CMYK Color from the Mode submenu of the Image menu. ■ device Whenever you convert an image from one mode to another, independent Photoshop transforms whatever color is displayed in a particular to its Lab equivalent, and then converts the Lab equivalent to the appropriate color in the targeted color mode. The L*a*b model is used 134 | C HAPTER THREE||

as the intermediate system because it is device independent. That is, it creates consistent color output regardless of the monitor, computer, or being used. As a printing and publishing professional, you will spend most of your time working with RGB and CMYK images. Therefore, this chapter concentrates on those two color models. You may be asked to prepare images in Indexed Color mode for electronic distribution. A detailed procedure for using the Indexed Color mode is provided in Chapter 9.

The RGB (Additive) Color Model

Many people think that things possess an attribute called color. For example, a person might say, “that apple is red,” or “this sweater is blue.” Unfortunately, these statements are completely false because color is not intrinsic in an object—rather it is caused by light reflecting from it. If you really think that an apple is red, or a sweater is blue, try identifying the color of an object while standing in a completely dark room. Obviously, you can’t tell what color things are in a dark room. So, it is obvious that color comes from light. Humans see colors that are either reflected from, transmitted through, or emitted by an object. In the case of an apple, you see the color that is reflected by it. The light comes from some source—a lamp or the — strikes the apple, and is reflected back to your eye. If no light strikes the apple, you don’t see anything. In the case of a television set or , small beams of light are emitted from the screen—you see the colors that are emitted.

Electromagnetic Energy ■ electromagnetic Light is one of several forms of electromagnetic energy that is emitted by the sun and by many types of artificial . In addition to light energy, the sun emits rays, X-rays, radiation, heat, and various types of sound. Each of these forms of energy travels in waves and can be measured by its . The waves can be organized, from shortest to longest, in a diagram called the (Figure 3.1). Some waves can be seen by humans (light), while some can be heard (sound) and others felt (heat). || Color Models | 135

Figure 3.1 LIGHT Radio waves The Electromagnetic X-ray Ultra Heat TV Short BC Spectrum Gamma ray Radar FM wave Long waves

10–11 10–6 10–4 10 10 8 centimeters

Ultraviolet Blue Yellow Red Violet Green Infrared 400 500 600 700 millimicrons

■ Figure 3.1 indicates that light waves are a very small part of the electromagnetic spectrum. Light waves range from 400 millimicrons in length (ultraviolet) to 700 millimicrons (infrared—heat). All these waves are visible to humans and comprise the visible spectrum. Several of the specific wavelengths of light are given names—500 millimicrons is called blue, 540 millimicrons is called green, and so on. The visible portion of the electromagnetic spectrum can be viewed in color. For example, if you pass white light through a prism, you can see the visible spectrum. A is another manifestation of the visible spectrum, and a printed example is shown as Figure 1 in the color insert.

Primary Colors of Light

■ primary colors Three of the colors of light—red, green, and blue—dominate the visible spectrum and are called primary colors. Note that blue is at the ■ secondary colors left side of Figure 1, while green is in the center, and red is at the right. The primary colors are very important because their wavelengths can be mixed together to create all the other visible colors. If you were to set up three separate slide projectors and put an image of a red circle in one, a green circle in the second, and a blue circle in the third then project all three beams of light onto a screen, you could make four other colors as shown in Figure 2 in the color insert. Three of these new colors are called secondary colors and include magenta (red plus blue), cyan (green plus blue), and yellow (green plus red). White is created by combining equal amounts of all three primary colors—red plus green plus blue. 136 | C HAPTER THREE||

All your previous experience will probably cause you to scream “you can’t make white from red plus green plus blue.” When working with ink or paint, you’re right. However, in the scenario described, waves of energy are being added together. Any time you add more than one source of energy together, the result is stronger than any of the individual components. For example, if you were to put one heat lamp above a rack of french fries at a restaurant, the fries would rise to a certain temperature. If, however, you were to put two heat lamps above the rack, the fries would get hotter because two sources of energy are heating them. So, too, with color. Adding together two or more sources of light energy always results in a brighter and stronger color than any single component. What about black? Isn’t black a color? Simply stated, no! Black occurs when there is no light—for example, when you’re in a completely dark room. Therefore, black is the absence of color because it only appears when there is no light. ■ additive model Because waves of red, green, and blue are added together to make new colors, this color system is called the additive model or RGB model. The additive system is used in sets, computer monitors, recorders, and . It is not used when mixing , inks, or paints. Virtually any color can be created using the additive system. Yellow is composed of full-strength red plus full-strength green. Combining green and blue light results in cyan, while adding red plus blue makes magenta. White is made by combining equal amounts of red, green, and blue. Other colors can be created by using more of one color than another. For example, orange can be made by combining full strength red with one-fourth strength green. || Color Models | 137

Exercise 3.1 Opening a Color Image In this exercise, you will open a color image composed of additive colors and set the Preferences so that you may view each color separately.

1. Turn on your computer, then erase the Photoshop 4.0 Prefs from the Preferences folder within the System folder using the procedures described in Chapter 1, if necessary.  Turn on your computer, then delete the Photos40.PSP file from the Adobe/Photoshop/Prefs subdirectory using the procedures described in Chapter 1, if necessary. If you are using your own computer and have not made any changes since you completed Chapter 2 of this text, you do not need to do this step. 2. Launch Photoshop 4.0, then make any necessary adjustments to the application so that it resembles Figure 1.8 on page 10. 3. From the , choose Open. 4. Navigate to the Photoshop Student Files folder, open the C3exercise.eps ( C3exer.eps) file, then click OK when the locked file message appears. C3exercise.eps ( C3exer.eps) opens in its own document window. Notice that the title bar indicates that the image is an RGB (additive) color file (see Figure 3.2). If the title bar is not completely visible, drag the window border until all the image and the title bar is visible. 5. Click the Channels tab found on the Layers/Channels/Paths palette in the lower right corner of the screen (see Figure 3.2). 6. If necessary, click the Zoom box on the right end of the Layers/ Channels/Paths title bar so that the palette expands to show all the channels (Figure 3.2).  If necessary, click the Expand Palette box to the left of the Close box on the right end of the Layers/Channels/Paths title bar so that the palette expands to show all the channels. 138 | C HAPTER THREE||

Figure 3.2 The expanded Layers/Channels/ Paths palette 3

1. The Layers/ Channels/Paths zoom box 2. The Channels tab 3. The color image is displayed in the RGB (additive) system. 2 1

8. From the File menu, choose Preferences, then select Display & Cursors. The Preferences opens (Figure 3.3).

Figure 3.3 The Preferences dialog box dis- playing the Display 1 & Cursors options

1. Check this option to display each color channel in its appropriate color.

9. In the Display section, select the Color Channels in Color option. Selecting this option instructs Photoshop to display each of the individual color channels in its appropriate color. When working with color documents, you should view the channels in color. 10. Click OK to close the dialog box. || Color Models | 139

Notice that each channel in the Channels palette is now displayed using the appropriate color and black. Black indicates any part of the image that does not contain the channel’s color. The area behind each strip is highlighted, indicating that the channel is currently displayed on the screen. The shortcut keys for each channel are displayed to the right of the channel name.

Exercise 3.2 Experimenting with an Additive RGB Image In this exercise, you will experiment with the combinations that can be achieved using individual and combined RGB channels.

1. On the Channels palette, click the Red image icon or use the keyboard shortcut + .  On the Channels palette, click the Red image icon or use the keyboard shortcut + . Notice that the other icons are no longer highlighted and the image on the screen is composed of only red and black. The title bar changes to reflect the channel that is displayed. The red portion of the image indicates any area that is composed of red light. The black portion of the image indicates any area that is not composed of red light. Notice that the entire background is red (Figure 3.4).

Figure 3.4 1 2 3 The Red channel displayed on the screen

1. Areas not composed of red light 2. Indicates Red channel is displayed 3. Areas that are composed of red light 140 | C HAPTER THREE||

2. Press , then click the Green image icon on the Channels palette. Both the red and green channels are activated and displayed on the screen. Pressing allows you to add to the current selection. Notice that the red and green channels combine to make yellow. The background has turned yellow in addition to every color inside the image that contains both red and green. Areas of the image that contain only red light are still displayed in red while areas that contain only green appear in green. Areas that do not contain either red or green appear black. 3. Press , then click the Green image icon on the Channels palette to deselect the green channel. Once again, the image appears only red and black. 4. Press , then click the Blue image icon on the Channels palette. The background appears magenta, along with any other color containing both red and blue. Red-only areas appear red, while blue- only areas appear blue. The black areas contain neither red nor blue. 5. Press , then click the Red image icon on the Channels palette to deselect the red channel. The image appears only in blue and black. 6. Press , then click the Green image icon on the Channels palette. The background and all colors that contain both blue and green appear cyan. Those areas containing only a single color appear that color. Those areas that contain neither green nor blue appear black. 7. Click the RGB icon on the Channels palette. All the colors appear. Notice that the circles enclosing the colors appear black on each individual channel and also appear black when all the channels are turned on together. To create black, no on your monitor are turned on. This proves what was stated earlier: black is the absence of color. Based on this exercise, you should know that additive RGB colors are combined to create each of the colors shown in Table 3.1. || Color Models | 141

Table 3.1 Additive RGB colors and their combinations

Red Green Blue Color Component Component Component Red X

Green X Blue X

Yellow XX

Magenta XX

Cyan XX White XXX

Black

Exercise 3.3 Creating Colors Using the Additive RGB System In this exercise, you will learn how RGB colors are defined using Photoshop Tone Values and create new additive colors using the Picker palette.

1. Click the Info palette menu triangle, then select Palette Options. The Info Options dialog box appears. 2. Press the First Color Readout pop-up menu, then choose RGB Color.  Press the First Color Readout pop-up menu, choose RGB Color and change the Mouse Coordinates to Inches. This will cause the Info palette to display the Photoshop RGB Tone Values for the colors on the screen. 3. Click OK. 4. From the Window menu, choose Show Color. The Color/Swatches/ Brushes palette appears (Figure 3.5). 142 | C HAPTER THREE||

Figure 3.5 The adjusted document window 4 1 2 1. RGB tonal values displayed in the Info palette 2. The Color tab 3 3. The Color/Swatches/ Brushes palette 4. The Paintbrush tool 5. The Foreground Color 5 selection box

5. Select the Eyedropper tool, then move the Eyedropper pointer into the yellow area at the top of the color image. Notice the Info palette indicates that the yellow area is composed of both red and green and that each has a Photoshop Tone Value of 255. 6. Move the Eyedropper pointer into each other color area. Check the Info palette for the Photoshop Tone Values of red, green, and blue. In the Color palette, click the Foreground color selection box (see Figure 3.5) to select it, if necessary. (Note: A appears around a selected color selection box.) Then drag the R to 255 and the G slider to about 84. The B slider should be at 0. Alternatively, you can type the values in the fields to the right of the sliders. Notice the color of the Foreground color selection box turns orange. If you mix approximately three-fourths red with approximately one- fourth green, the result will be an orange color. You can make virtually any color by mixing varying amounts of red plus green plus blue. 7. Select the Paintbrush tool (see Figure 3.5 for its location), then use it to paint some lines on the bottom of the C3exercise.eps ( C3exer.eps) image (see Figure 3.6). 8. Select the Eyedropper tool, then measure the red, green, and blue Photoshop Tone Values of the orange lines you just painted. || Color Models | 143

The Info palette should read approximately R:255 and G:84 (Figure 3.6). Note: Don’t worry if your values are not exactly R:255 and G:84. Your stripes will appear lighter at the edges and darker at the center if a soft-edged brush has been selected from the Brushes palette. As a result, the RGB values may fluctuate within the lines you painted.

Figure 3.6 The Photoshop Tone Values of orange 2

1. Orange area painted on the image and measured by the Eyedropper 3 2. Red and Green Photoshop Tone Values for orange 3. The orange color 4 shown in the Foreground Color selection box 1 4. The Red and Green sliders set to make orange

9. From the File menu, choose Save As. Then save the image on your Photoshop Files 1 disk or folder in the Photoshop EPS format using the name Project3.eps. Accept the EPS Format defaults.

The CMYK (Subtractive) Color Model

Although the additive system is fine for displaying colors on a computer monitor or a television set, the additive colors cannot be used to print colored images, paint with oil colors, or fabrics. In these cases, colors of light are not added—rather pigments are combined to create new colors. To print colored images, colors of ink must be mixed or superimposed to create new colors. If the additive RGB colors were used in printing, superimposing any two colors would result in black (see Figure 3 in the color insert). 144 | C HAPTER THREE||

Process Colors

■ process colors Instead of using additive RGB colors, printing machines use cyan, magenta, and yellow inks. These three colors, known as process colors, are the same three secondary colors that can be made by mixing equal amounts of red, blue, or green light (see Figure 2 in the color insert). The in each of the three process color inks transmits only two additive NOTE colors—cyan transmits both blue and green, magenta transmits red and Sometimes printing blue, and yellow transmits red and green. The pigment in each process technicians erroneously refer to cyan as process color ink absorbs the color it does not transmit. Thus cyan ink absorbs blue and magenta as red, magenta ink absorbs green, and yellow ink absorbs blue. process red. Process color inks are transparent. When two or more process color inks are superimposed, light travels through the layers of ink to the paper and is then reflected back up through the ink to the viewer. If process color inks are superimposed, the only color of light that can pass through all the layers of ink is the color that all the colors share. For example, yellow and cyan both transmit the color green. So, when yellow is printed over cyan the result is green. Similarly, printing magenta over cyan yields blue (both magenta and cyan transmit blue) and printing yellow over magenta yields red (both yellow and magenta transmit red) (see Figure 4 in the color insert).

Subtraction of Color ■ subtractive Process inks are usually printed on white paper. When light strikes a model sheet of white paper, the red, green, and blue components of the light are ■ process color reflected by the paper. Printing a layer of process color ink on white printing paper blocks some of the light that is reflected from the paper. For example, if you print yellow ink on white paper, the yellow transmits the red and green light that is reflected from the white paper, but not the blue light. Thus, it can be said that yellow ink subtracts blue because it blocks the blue light that is reflected from the white paper. In the same way, magenta subtracts green and cyan subtracts red. If you print yellow on top of magenta on top of cyan, all the additive colors are theoretically subtracted from the paper (see Figure 5 in the color insert). Because cyan, magenta, and yellow each subtract a color from paper, this system is sometimes called the subtractive model. The subtractive model can also be called process . || Color Models | 145

Using process color inks, you can create approximately the same colors as you can with the additive system. The colors and their components are shown in Table 3.2 and illustrated in Figure 4 in the color insert.

Table 3.2 Cyan, magenta, and yellow and their combinations

Color Cyan Magenta Yellow

Red XX

Green XX

Blue XX

Yellow X

Magenta X

Cyan X

White

Black XXX

To create colors other than those shown in Table 3.2, dots are used. In the same way you made orange by mixing a lot of red with a little bit of green in Exercise 3.3, varying sizes of halftone dots of each of the three process colors plus black can create hundreds of thousands of colors. A few of the colors that can be created using various percentages of CMY are shown in Figure 6 in the color insert. Figure 17 in the color insert illustrates how clusters of cyan, magenta, yellow, and black halftone dots create different colors. The entire photograph is composed of halftone dots, but only those in the highlighted square have been enlarged so that you can see them without a magnifier.

Deficiencies in Process Colors Notice the black area at the center of Figure 4 in the color insert. Theoretically, each of the process colors should completely subtract one from the paper—after all three process colors are printed there should be no color left (black). However, the pigments used in process color inks are imperfect—each process color does not completely subtract the additive color it should—for example, magenta does not remove all 146 | C HAPTER THREE||

NOTE the green. Therefore, a little bit of color is left after all three process colors If you are a graphic have been printed. The result is a muddy chocolate instead of a designer or illustrator crisp black. Because this muddy brown is not sufficiently black, printers and often create color artwork from scratch usually print a layer of black ink over any areas that are composed of all using Photoshop’s three process colors to cover the muddy effect. As a result, most color image creation tools, printing is done with four colors of ink: cyan, magenta, yellow, and black. you should build your colors using the color These colors are often abbreviated with the acronym CMYK (K is used to system that will be used signify black—using B would cause confusion with blue). to view your finished work. If you are The imperfect nature of the pigments used in process color inks preparing print media, impacts printed colors as well as black. A perfect cyan ink would transmit you should create your all the blue and green light that strikes it while subtracting all the red. colors in CMYK because Photoshop will not need However, most cyan inks transmit a little red and subtract some of the to convert those colors blue and green that they should reflect. Similarly, most magenta inks to CMYK and, thus, the gamut problem is transmit a little bit of green and subtract some red and blue. Yellow is avoided. If you build the most perfect process ink—it transmits most of the red and green that colors in RGB for print strikes it while subtracting most blue (see Figure 7 in the color insert). media, you will often be disappointed with If you look carefully at Figure 7, you will notice that less red, green, the CMYK equivalents. and blue light is transmitted through layers of cyan, magenta, and yellow If, however, you are designing work for inks than should be. In particular, the overlapping of the process inks computer distribution provides far too little blue, somewhat too little green, and almost the (such as via the Internet right amount of red. As a result, color images printed using CMY inks or CD-ROM), always build colors using RGB are always very deficient in blue and somewhat deficient in green. Because because that is the color red is the color most reflected by superimposed process inks, printed system used by color monitors. photographs can tend to take on a reddish cast unless compensations— called color corrections—are made (see Chapter 5 for an introduction to color correction).

Color ■ gamut Due to the deficiencies in the transmission and subtraction qualities of process inks, many colors cannot be reproduced accurately using CMYK inks. When a particular color cannot be reproduced using CMYK, that color is said to be out of the CMYK gamut. A gamut is the range of colors that a particular device or process can produce. A human with normal eyesight can perceive all visible colors—the entire visible gamut. Color film can reproduce most of the visible colors and has a very large gamut. CMYK inks printed by offset can only produce a relatively small gamut of colors. Ink printed on newsprint has perhaps the smallest gamut (Figure 3.7). You can see many thousands of colors || Color Models | 147

that CMYK cannot reproduce. In addition, your monitor can display hundreds of colors that cannot be printed using CMYK inks. Whenever a color is displayed on the screen that is out of the CMYK gamut, Photoshop warns you through the use of an exclamation point (!). You can then instruct Photoshop to substitute the closest possible CMYK color.

Figure 3.7 5 Gamuts of selected reproduction y y y y processes green 1. Visible gamut of yellow colors cyan white 2. Color gamut that can red be reproduced by blue magenta color film x x x x 3. Color gamut that can be reproduced using 1 2 3 4 CMYK inks with offset lithography 4. Color gamut that can be reproduced using newsprint 5. Boundaries of visible gamut

Reproducing Color Photographs Using Process Color Printing

■ tristimulus Desktop scanners measure the colors in a color original and then value usually divide the image into red, green, and blue channels. The red, ■ lookup table green, and blue channels must then be separated into CMYK channels using Photoshop so that the image can be printed. The scanner measures every point of a photograph three times to determine how much red, green, and blue the point reflects. These three measurements are known as tristimulus values. Photoshop uses a lookup table to convert an individual point’s tristimulus value to CMYK halftone dot values. The values in the lookup table can be adjusted by the Photoshop technician using several dialog boxes that will be discussed at length in Chapter 4. Drum scanners usually directly separate the original image into four different channels—one each for CMYK—so no additional color separation by Photoshop is necessary. No matter if the image was originally scanned in RGB and converted to CMYK or originally scanned in CMYK, the final color separations are almost always CMYK. 148 | C HAPTER THREE||

NOTE Because RGB and CMYK have different color gamuts, Photoshop Your computer always will often be unable to find an exact match for an individual pixel’s displays colors using tristimulus tone value in its CMYK lookup table. In those cases, the RGB model. Even if you are using the Photoshop will convert the RGB color to the closest possible CMYK CMYK model, Photoshop color. Many times the closest CMYK color is very different from the must convert the CMYK original RGB color because the CMYK gamut is much smaller than the colors to RGB to be able to display them on the RGB gamut. screen. Keep in mind that what you see Handling Out-of-Gamut Colors on the screen is a simulation of the Many printing and publishing professionals do not like the way actual CMYK color Photoshop converts colors from RGB to CMYK, especially in its handling and that what you see is not necessarily what of out-of-gamut colors. Whenever Photoshop encounters a color that is you will get when the out of the CMYK gamut, the program simply replaces it with the closest colors are printed on available color. Unfortunately, nearby colors that are not out-of-gamut a printing press. are not changed. As a result, the relationship between adjacent colors can be badly altered by Photoshop. High-end drum scanners and other color separation programs solve this problem by changing an entire range of colors to accommodate an out-of-gamut color. Thus, the relationship between nearby colors is preserved. Although Photoshop’s method for converting an image from RGB to CMYK may have drawbacks, it is important to remember that it works well for most images. You should also remember that a desktop scanner and Photoshop are relatively inexpensive (as compared to high-end scanners and proprietary software) and that these items have, in large part, made possible the proliferation of color images you see in publications ranging from the daily newspaper to company newsletters.

Outputting Separations Each CMYK separation is output to an imagesetter or other device that records the image using varying sizes of halftone dots. A separate plate is produced for each of the four process colors. Each color is printed separately using the appropriate process color ink on a printing press. After all four colors are printed, the overlapping colors produce a simulation of the original photograph (see Figure 8 in the color insert). The order in which the process colors are printed, called color sequence, can impact the appearance of a color reproduction. While the four process inks (CMYK) can be printed in twenty-four possible sequences, three combinations are common: YMCK, CMYK, and KCMY. || Color Models | 149

To increase the predictability of color reproductions and to keep costs to a minimum, most printing companies prefer to keep their color sequence constant in all but the most rare circumstances. Printing yellow last can often cause problems. In particular, yellow is the most opaque process- colored ink. Printing it on top of the other colors can cause the of the image to be skewed toward yellow. In addition, printing yellow last can cause the shadows to look lighter than they would otherwise appear. For this reason, many color experts recommend that process colors be printed in either the YMCK or CMYK sequence.

Exercise 3.4 Inspecting the Out-of-CMYK-Gamut Areas of an RGB Image In this exercise, you will use Photoshop features to inspect the out- of-gamut areas of the Project3.eps image and prepare a copy of the image that you will then use to compare the RGB image with the equivalent CMYK image after the conversion process is complete.

1. Be sure the Eyedropper tool is still selected, then move the Eyedropper pointer into the red area at the top left of the image. 2. Look at the Info palette in the CMYK section (Figure 3.8). Notice that the red area would be composed of approximately 93% magenta halftone dots and 100% yellow halftone dots if it were printed using process inks (your numbers may vary slightly). These are the halftone dot values Photoshop found in its lookup table that most closely match the Photoshop Tone Value of the red color. Also notice the exclamation points that appear next to each of the CMYK fields. The exclamation points indicate that the sampled color is outside of the CMYK gamut. The color is reproducible on screen because it is in the RGB gamut but will not appear the same color when printed. 150 | C HAPTER THREE||

Figure 3.8 The Info palette displaying an out- of-gamut alert 2 1. CMYK equivalents of a 255 Red Photoshop Tone 1 Value 2. Out-of-gamut alerts 3. From the View menu, choose Gamut Warning. In a few seconds, the image appears totally in gray. Photoshop uses its lookup table to identify every color in the image that is outside the CMYK gamut. It then displays the out-of-gamut colors on the screen in gray. Notice that all the colors on the image are outside of the CMYK gamut because they are all displayed in gray. 4. From the View menu, choose Gamut Warning again to deselect it. 5. From the View menu, choose CMYK Preview. In a few seconds, the image is displayed using less-intense colors. Photoshop has replaced each out-of-gamut color with the closest in- gamut CMYK color. 6. Use the Eyedropper tool to sample several colors in the image. Look at the Info palette and notice that the out-of-gamut alerts are still displayed because you are looking at a CMYK preview—Photoshop still remembers the actual colors in the file. 7. From the View menu, choose CMYK Preview again to deselect it. The image appears in the RGB gamut again.

When converting an image from RGB to CMYK, you should have a copy of the original image on the screen so that you can see where you have been as well as the current condition of the image. You can make a copy of an image using the Duplicate command from the Image menu. . 8. From the Image menu, select Duplicate. The Duplicate Image dialog box appears (Figure 3.9). || Color Models | 151

Figure 3.9 The Duplicate Image dialog box

9. Accept the defaults, then click OK. A window named Project3.eps copy appears on the screen. The copy is not saved to disk, however.  Accept the defaults, then click OK. A window named Project31 appears on the screen. The copy is not saved to disk, however.

NOTE 10. Be sure the copy is active—an active window’s title bar ( ) contains black horizontal stripes or () is highlighted. Then from the View If the window does not shrink to the size of the menu, choose Zoom Out. If necessary, choose Zoom Out again until image, drag the window the copy is displayed at 50% magnification. border so that it is the same size as the image. 11. Use the title bar to drag the copy to the right of the original as illustrated in Figure 3.10.

Figure 3.10 An image and its 1 2 3 duplicate displayed

1. The original image 2. The copied image reduced to 50 percent and repositioned 3. The horizontal stripes indicate this window is active 4. File size box

NOTE If the resolution of 4 your monitor is less than 800 × 600 or a different size from the one used to capture the images for your textbook, then you may not be able to arrange your screen elements exactly as shown in Figure 3.10. 152 | C HAPTER THREE||

Exercise 3.5 Performing a Color Separation In this exercise, you will produce a color separation of an image and compare it to the original RGB image.

1. Select the full size original image by clicking anywhere on its title bar. Notice the size of the file in the File Size box (see Figure 3.10). The title bar indicates the window is active. 2. From the Image menu, choose Mode, then select CMYK Color. In a few seconds, the color-separated CMYK version of the original RGB file appears on the screen. The half-sized copy is still an RGB image. Note that the colors are less brilliant than those in the RGB copy. In particular, notice the extremely poor reproduction of the blue area at the bottom of the image. This occurs because of the overall deficiency of blue in CMYK reproductions. 3. Look at the File Size box beneath the ( ) document window or () program window. Notice that the file size has increased from 245K to 327K. The file size increased by one third because Photoshop had to add a fourth channel—the black channel. NOTE 4. Use the Eyedropper pointer and the Info palette to check the CMYK Remember that halftone dot values of all the colors in the CMYK image. Notice Photoshop is still that all the colors are within the CMYK gamut because no displaying the colors exclamation points appear next to the CMYK fields in the Info using RGB because computer monitors palette. always display colors in RGB. It is converting the All the colors are in the CMYK gamut because they were built using CMYK values displayed the CMYK system rather than the RGB system. in the Info palette to matching RGB values to 5. Measure the green area of the CMYK image using the Eyedropper display on the screen. pointer. Note the CMYK values in the Info palette (C74, M0, Y92, K0) and the RGB values (R84, G168, B61). (Note: It is not important if your monitor displays slightly different numbers from these.) 6. Move the Eyedropper pointer over the green area of the duplicate (RGB) image. Note that the Info palette fields are all blank. || Color Models | 153

7. Press and hold the mouse . The Eyedropper pointer now measures the color in the nonactive RGB image. NOTE Note the values in the RGB section of the Info palette: (R0, G255, When you choose Save from the File menu, B0) and in the CMYK section (C74, M0, Y92, K0). Photoshop makes an additional copy of your 8. Compare the numbers you measured in Step 5 with those you file on the disk and measured in Step 7. saves the previous copy to be used to Revert. If Notice that the RGB values are very different in the CMYK image you are saving on floppy as compared to the duplicate (RGB) image. In the RGB image, the disks, your disk is nearly full and cannot hold an green area contains only green. However, in the CMYK image, the additional copy of the green area also contains some red and blue. This occurs because the image, so an alert cyan ink used to make the green color in CMYK reflects some red. stating your disk is full will probably appear. If Similarly, the yellow ink in CMYK reflects a little blue. As a result, this happens, choose the green area is darker and more muddy in CMYK than in RGB. Save As, click Save, click Replace, accept the EPS The CMYK values in both Step 5 and Step 7 are the same because in Format defaults, then both cases Photoshop displays the CMYK values that most closely click OK. Photoshop will now erase the old match the RGB values. Project3.eps file and replace it with the new 9. Repeat Step 7 to measure the red and blue areas of both the CMYK one. You will not have and RGB images. a file to revert to, however. 10. From the File menu, choose Save to save your changes.

Exercise 3.6 Experimenting with a Subtractive CMYK Image In this exercise, you will experiment with the combinations that can be achieved using individual and combined CMYK channels.

1. Click the Zoom box on the right end of the Layers/Channels/Paths title bar so that the palette expands to show all four component channels and the composite CMYK channel (Figure 3.11).  Click the Expand Palette box to the left of the Close box on the right end of the Layers/Channels/Paths title bar so that the palette expands to show all four component channels and the composite CMYK channel. 154 | C HAPTER THREE||

Figure 3.11 The Layers/ Channels/Paths palette expanded to display all CMYK channels

2. On the Channels palette, click the Cyan image icon or use the keyboard shortcut + . Notice that the highlighted background disappears behind the other icons in the Channels palette and that the image on the screen is composed of only cyan and white. The title bar changes to reflect the name of the channel that is displayed. The cyan image indicates any area that will be composed of cyan ink. Each cyan area has a different halftone dot value to indicate the percent of cyan that will be necessary to superimpose with the other process colors to make the desired overprint color. These values can be read using the Eyedropper pointer and the K field in the CMYK section of the Info palette (separations are black-and-white images, so the halftone dot value is indicated in the K field) and are shown on Figure 3.12. The white image indicates any area that will not be printed—it will remain white paper. Notice that the black circles that enclose the colors are included as part of the cyan image. This is because black is created by superimposing cyan, magenta, and yellow (Figure 3.12). || Color Models | 155

Figure 3.12 The Cyan Channel 1 displayed on the 6 2 screen

1. 3% cyan 2. 75% cyan 3. 50% cyan 4. 96% cyan 5. 43% cyan 6. 65% cyan 5 3

NOTE 4 Your values may vary

3. Press , then click the Magenta image icon on the Channels palette. Both the cyan and magenta channels are activated and displayed on the screen. Notice that the cyan and magenta channels combine to make various bluish colors. Areas of the image that will be printed with only cyan ink are still displayed in cyan, while areas that will be printed only with magenta appear only in magenta. Areas that do not contain either cyan or magenta appear white. 4. Press , then click on the Yellow image icon. All three color channels are now displayed on the screen. The image is now almost complete. However, notice that the black lines enclosing the colors are weak and insubstantial. Overprinting all three process colors does not result in a good solid black. 5. Press , then click on the Black image icon. The completed image is now displayed. The black image contains only those areas that contain overprinted cyan, magenta, and yellow. The black image serves to darken those overprinted areas. 6. Use the Channels palette to display each of the following combinations of process colors: cyan plus yellow (note the green colors that are created wherever cyan and yellow overlap); cyan plus black; magenta plus yellow (note the red colors that are created wherever magenta and yellow overlap), magenta plus black; and yellow plus black. 156 | C HAPTER THREE||

7. Click the CMYK icon on the Channels palette. All the colors appear.

Exercise 3.7 Creating Colors Using the Subtractive CMYK System In this exercise, you will create and use new subtractive colors using the Color palette.

1. Be sure the Color palette is displayed on the screen. Then create the following color using the RGB sliders: R54, G247, B143. Alternatively, you may type the numbers into the appropriate fields. This color is out of the CMYK gamut, so Photoshop displays an exclamation point alert triangle in the Color palette (in the bottom left corner) and displays the closest possible CMYK equivalent (Figure 3.13).

Figure 3.13 The Color palette 3 displaying an out- of-gamut alert and the closest CMYK equivalent

1. Out-of-gamut alert 2. Closest CMYK equivalent 3. The Color palette 1 2 menu triangle 2. Click the Closest CMYK Equivalent box. The closest CMYK equivalent has approximately the following values: R118, G185, B140. It is time consuming and frustrating to build colors using the RGB palette and then let Photoshop pick the closest CMYK equivalent. Fortunately, Photoshop allows you to build colors directly using the CMYK process colors. 3. Press the Color palette menu triangle (see Figure 3.13), then select CMYK Sliders. The Picker palette expands to include sliders for the process colors and black. The same color chosen in Step 2 still appears in the Foreground Color selection box, but now the sliders indicate the color’s CMYK components: C62, M0, Y56, K0. (Note: Don’t worry if slightly different numbers are displayed on your monitor.) || Color Models | 157

4. Build a color composed of the following percents using the CMYK sliders: C39, M100, Y14, K11. (Note: If you prefer, you can type the percent numbers directly in the fields to the right of each slider.) Notice that no alert or equivalent color appears in the lower right corner of the Picker palette. Because the color was built using CMYK process colors, it is within the CMYK gamut. 5. Choose the Paintbrush tool, then paint some stripes in the lower right corner of the document window. 6. Use the Eyedropper tool and Info palette to measure the color of the stripes you just painted. The color should measure approximately R128, G0, B82; and C39, M100, Y14, K11. Once again, don’t worry if your numbers are slightly different. 7. Close Project3.eps. When prompted, save your changes. Once again, if an alert appears indicating that your disk is full, use the process described in Step 10 of Exercise 3.5. Then from the File menu, choose Close. 8. The half-size copy of the original file should now become active. If not, click the duplicate’s title bar. 9. Close the half-size copy of the original. When prompted, do not save the file.

Factors Affecting the Perception of Process-Color Printing When a printed CMYK reproduction is inspected, the colors perceived by the viewer are those that are reflected from the white paper through the layers of ink. The perceived color is obviously affected by the color of the ink—if the wrong colors of ink are used, the reproduction will also be the wrong color. In addition, if one or more inks are not sufficiently transparent, an inadequate amount of the appropriate colors of light will pass through them. This inadequate transmission of light causes a shift in the reproduction’s color.

Affect of Paper Color on Perceived Color

■ color cast Perceived color is also affected by the color and absorption qualities of the paper. There are many paper in addition to many 158 | C HAPTER THREE||

colors of paper—if a certain paper does not reflect equal amounts of red, green, and blue light, then the reproduction will have a color cast. Many white papers have a slight yellowish tinge because of the natural color of the wood fibers from which they are made. The yellowish tinge means an insufficient amount of blue is being reflected from the paper. This poor reflection of blue light on the part of the paper, coupled with the insufficient transmission of blue light by the process color inks, often results in a color reproduction that is lacking in blue. Reproducing a color photograph on colored paper causes the color balance of the entire image to shift toward the paper’s color. For example, printing a process color image on yellow paper will cause a yellow color cast in the image.

Affect of Paper Absorbency on Perceived Color Some papers are more absorbent than others. For example, uncoated papers are generally more absorbent than coated sheets. More absorbent papers absorb more ink, and excessive ink absorption results in two consequences. First, ink that is absorbed into paper is not available on the surface to be seen. Thus, images printed on very absorbent paper appear more pale than they would if printed on a less-absorbent paper. Second, more absorbent papers increase dot gain, which leads to muddy midtones.

Affect of the Light Source on Perceived Color Perhaps least considered among the variables affecting the color of a printed reproduction is the light source itself. To be most effective, color prints should be viewed in white light. By definition, white light contains equal amounts of red, green, and blue light. However, virtually no artificial light source emits equal amounts of red, green, and blue. And, the sun’s light only appears white in outer space or on clear, smogless days around noon! Common artificial light sources include incandescent (tungsten) screw-in light bulbs that you probably have in your living room lamps and the fluorescent light that probably your office or work space. Neither of these lights is anywhere near white—incandescent lights are very yellow and lack blue, while fluorescent lights are very green and lack red. You have witnessed this phenomenon if you ever photographed an interior scene without using . After your film was processed, you probably noticed that your photographs appeared either too green (if the room was illuminated with fluorescent lighting) or too yellow (if the room lighting was incandescent). || Color Models | 159

Artificial lighting also affects the apparent color of articles you purchase. You probably have had the experience of buying an article of clothing in a department store only to have the item appear black at home. This occurs because department stores have fluorescent lighting that contains lots of blue, while the incandescent lighting that you most likely have in your bedroom emits very little blue. If there is little blue in the light source, there will be little blue light reflected by an item or perceived by a viewer. The color of the light source also impacts the color of the printed reproduction. If a color print contains a lot of , it will appear too dark if viewed under incandescent lighting. Similarly, look dark and lifeless when viewed under fluorescent lighting. Figure 9 in the color insert illustrates the impact of three different light sources on the same print. ■ degrees Kelvin The color of light is measured using a special scale called degrees Kelvin (°K). The physics needed to fully explain the term “degrees Kelvin” is beyond the scope of this book. Suffice it to say, the higher the temperature, the bluer the light; and the lower the temperature, the redder the light. Table 3.3 identifies several sources of light and their approximate color temperatures.

Table 3.3 Common light sources and their color temperatures

Light source Approximate temperature, ° K

C0lear blue , midday 12,000 to 26,00

O0vercast sky, midday 6,700 to 7,00

N0oon sunlight, clear day 5,400 to 5,80

S0unset 2,00

C0ommercial fluorescent 6,50

“Warm white” fluorescent 3,000

T0ungsten incandescent 2,650 to 3,40 160 | C HAPTER THREE||

If two people look at the same color print under different light sources, they will, without a doubt, see different images. To standardize viewing conditions, the printing and publishing industries have adopted a special fluorescent light source that emits a of 5,000°K. This color temperature is the closest that artificial lighting can come to noon sunlight on a clear day. No color print or proof should ever be judged using any other light source. Miscommunication will always occur if standardized lighting is not used. To adequately judge any color reproduction, the light source, paper, and ink must all be considered. Each of these variables must be taken into account during the tone and color correction process.

Other Color Models

Thus far in this chapter, you have been exposed to two color models: RGB and CMYK. You also know that the same color can be defined using the terms of more than one model. For example, you already know that the same color can be defined as R128, G0, B82 or as C39, M100, Y14, K11 (you defined this color in Exercise 3.7). Although RGB and CMYK are among the most common color models, Photoshop provides additional models that you can use to specify colors. These include HSB, L*a*b, and several Spot Color systems. Each of these additional models is explained in further detail in the following paragraphs.

HSB Color The HSB model is based on the intuitive perception of color by humans. In this model, H, refers to hue, S means saturation, and B stands for brightness. ■ hue Hue is the name of a color, and refers to its wavelength on the ■ electromagnetic spectrum (see Figure 3.1). Red, orange, yellow, and blue are all names of . Hues are typically arranged around a circle called a color wheel. Numerically, hues are expressed in degrees from 0° to 360°. As a frame of reference, red is both 0° and 360°, yellow is 60°, green is 120°, cyan is 180°, blue is 240°, and magenta is 300°. ■ brightness Brightness is the lightness or darkness of a color. When you say ■ tint “light blue,” you are referring to the brightness of a blue hue. A hue can ■ shade be lightened by adding white and darkened by adding black. Light hues || Color Models | 161

are typically called tints, while dark hues are called shades. In Photoshop, brightness values are measured from 0% (black) to 100% (pure color). ■ saturation Saturation, sometimes called chroma, is the purity of a color. Saturated colors are pure colors, while desaturated colors—sometimes called dirty colors—have been mixed with gray. In Photoshop, saturation values range from 100% (the pure color) to 0% (pure gray).

L*a*b Color L*a*b color, which is designated simply “Lab” in Photoshop, is an international standard used by color scientists to describe colors. Any color in the visual spectrum can be defined mathematically using this system—thus, it embodies the entire visual gamut. The L*a*b system is particularly useful for transforming an image in one model to another model because L*a*b contains all the colors in all the color modes. ■ lightness When using the L*a*b model, colors are defined using three ■ a channel channels—lightness, the “a” channel, and the “b” channel (hence the ■ b channel name L*a*b). Lightness refers to the lightness or darkness of a color—it only contains black-and-white data. The a channel contains color information and is a continuum ranging from magenta to green. Similarly, the b channel is a color continuum ranging from yellow to blue. Every color contains a given value of each of the three channels. The L*a*b model is the color model used internally by Photoshop to convert color images from one model to another. It is also recommended for transferring color images from one type of computer system to another. In practice, however, the graphics professional will seldom use it. However, it does have one major practical use. Colors specified in the L*a*b model can also be displayed in the Lab Color mode. Like all color modes, each Lab channel can be adjusted individually. Therefore, the lightness, or darkness, of a photograph can be adjusted using the Lab Color mode without harming the color content of the image. This can be very useful in color correction and will be discussed further in Chapter 5.

Spot Color

■ color palette A spot color is a single color of ink applied to portions of a printed sheet. An example of a spot color would be a red headline or green logo on a page where all other images are printed in black. Spot colors are generally identified using a number of commercially available color 162 | C HAPTER THREE||

palettes. Color palettes are preprinted samples of ink colors that are available in book form and are very similar to the color swatches you have probably seen in paint stores. Color palettes are usually available in hard-copy form from ink manufacturing companies or printing trade associations. Printing technicians can either buy or mix inks to match any of the spot colors depicted on any of the available color palettes. If necessary, most spot colors can be simulated using process inks. If, for example, a client uses a particular red spot color known as 185 for a letterhead’s logo, the color of the logo can be simulated in process color reproductions so that a special color of ink need not be printed. The CMYK percentages for PANTONE 185 would be approximately C:0, M:91, Y:76, K:0.

Photoshop Usually Converts Spot Colors to CMYK It is important to note that Photoshop almost always converts a specified spot color to its CMYK equivalent. Thus if you choose a spot color, Photoshop will print four separations—one each for cyan, magenta, yellow, and black. The only exception to this rule would be if you save an image in the Duotone mode (more on the Duotone mode can be found later in this chapter). In this case, Photoshop would output one page for each of the colors in the duotone.

Electronic Color Palettes Photoshop provides electronic screen versions of the color palettes distributed by several organizations (Figure 3.14). You should always remember that the colors displayed on the screen will not be the same as those printed on paper. For this reason, it is best to obtain actual printed color palettes to be used as guides when choosing spot colors rather than rely on the colors displayed on the screen. All spot color palettes are based upon printing the chosen color on white paper. You should not choose a spot color from a color palette and expect it to be the correct color if it is printed on green paper. Also, colored inks look different on coated paper as compared to uncoated paper. Be sure to use the correct color palette for the type of paper to be used to print the job. || Color Models | 163

Figure 3.14 Spot color systems available in Photoshop

• ANPA Color is a palette of 300 colors specified by the American Newspaper Association to be used when printing newspapers with color presses. • The DIC Color Guide is a system of 2,638 colors available from the Dainippon Inks and Chemicals Co. • FOCOLTONE is a system of 763 colors composed of various percentages of CMYK process colors. • The TOYO Color Finder is a system of 1,050 colors based upon the most commonly available printing inks used in Japan. • The HKS systems, which may not be included with your Photoshop program, are color libraries that are used in Germany and France.

The PANTONE MATCHING SYSTEM The most common spot color matching system used in the United States is the PANTONE MATCHING SYSTEM. To use the PANTONE MATCHING SYSTEM, a client must first choose a numbered color from over 700 spot colors displayed in the PANTONE Color Formula Guide. Then the printing technician uses specific proportions of ten basic color inks to physically mix the desired color. PANTONE colors can also be simulated using percentages of CMYK inks using the PANTONE ProSim palette. Unfortunately, PANTONE colors simulated using CMYK may not appear exactly the same as solid layers of the same numbered color because many PANTONE colors are outside the CMYK gamut. 164 | C HAPTER THREE||

Photoshop 4.0 contains a number of PANTONE MATCHING SYSTEM palettes from which you may choose. Table 3.4 describes each PANTONE MATCHING SYSTEM palette.

Table 3.4 PANTONE MATCHING SYSTEM color palettes

Palette Description

PANTONE Coated TPhe solid ANTONE MATCHING SYSTEM for printing on coated white paper.

PANTONE Process Uses CMYK color inks to produce more than 3,000 colors that are not PANTONE MATCHING SYSTEM colors.

PANTONE ProSim EPnables you to simulate the ANTONE MATCHING SYSTEM colors using process color inks on coated white paper.

PANTONE Uncoated TPhe solid ANTONE MATCHING SYSTEM colors for printing on uncoated white paper.

TRUMATCH Another spot color system that is becoming increasingly popular in the United States is the TRUMATCH system. Unlike other spot color systems, TRUMATCH uses percentages of CMYK to specify more than 2,000 colors. Because the colors have been created using CMYK instead of percentages of various spot colors, all TRUMATCH colors are within the CMYK gamut and can be accurately reproduced on press. TRUMATCH inks are based on fifty hue families, each divided into forty proportioned saturations and shades. In essence, TRUMATCH uses CMYK to create colors using the HSB model. In use, a client selects a color from the TRUMATCH Colorfinder—TRUMATCH 2-b3, for example. The “2” refers to the hue number, the “b” refers to its saturation, and the “3” to its black content. Hues range from 1 to 50 (red through brown), saturations range from “a” through “h” (most saturated to least saturated), and shades range from 1 to 7 (least to most black content). The printing technician is provided with a formula for each color listed in the TRUMATCH Colorfinder. For example TRUMATCH 2-b3’s formula is C0, M85, Y51, K18. Technicians could physically mix eighty- five parts of magenta ink with fifty-one parts of yellow and eighteen parts of black to make this color. However, it is more likely that halftone dot percentages of each process color would be specified using Photoshop or other means. || Color Models | 165

Accessing Color Models Color models can be accessed through the Color palette or the Color Picker dialog box. To choose a given color model from the Color palette, click the Color Palette Menu Triangle, then choose the model you wish (Figure 3.15). Sliders are then displayed for each individual channel used by the model. For example, if you choose the RGB model, a separate slider is displayed for red, green, and blue.

Figure 3.15 Color models displayed in the Color palette menu

The Color Picker To access the Color Picker, you must double-click the Foreground Color Selection Box or the Background Color Selection Box. These selection boxes are found both on the Tool palette and on the Color palette (Figure 3.16). Double-clicking a Foreground Color Selection Box lets you specify the color with which you want to paint, while double- clicking a Background Color Selection Box allows you to set the color that will be displayed if you erase an image. Both Foreground Color Selection Boxes—and both Background Color Selection Boxes—perform the same function. If you double-click one of them, any changes you make will be reflected in the other one. 166 | C HAPTER THREE||

Figure 3.16 Locations of the Foreground and Background Color Selection Boxes 1 2 1. Foreground Color Selection Boxes 2. Background Color Selection Boxes

After you double-click a color selection box, the Color Picker will be displayed on the screen (Figure 3.17). Notice that it contains several elements. The Color Field and the Color Slider allow you to choose colors visually. The Color Slider allows you to choose a hue—move the Color Slider until the hue you want is displayed in the Color Field. The Color Field allows you to visually specify saturation and brightness for the chosen hue. The top right corner of the Color Field displays the chosen hue with 100% brightness and 100% saturation. The color decreases in saturation horizontally from right to left—the top right is 100% saturated, while the top left is 0% saturated. Brightness decreases vertically from top right to bottom right—the top right is 100% bright, while the bottom right is 0% bright. All the colors displayed in the center of the Color Field are composed of various brightness and saturation levels of the chosen hue. If you move the pointer over the Color Field—the pointer changes to a circle—you can click the mouse button to choose a color. The selected color appears in the New Color Box. You can then compare the new color to the previous color displayed in the Previous Color Box. The components of a selected color are displayed mathematically in the HSB, RGB, L*a*b, and CMYK fields in the lower right portion of the dialog box. Instead of using the Color Slider and Color Field to choose colors, you can type values in the fields of the color model you are using. Equivalent values for the other color models are automatically displayed, the Color Slider moves to the correct hue, and the specified color is || Color Models | 167

displayed in the Color Field. If the specified color is out of the CMYK gamut, an exclamation point appears next to the New Color Box.

Figure 3.17 2 3 4 5 6 The Color Picker

1. Color field 2. Decreased saturation 3. Pure hue 4. Color slider 5. New color box 6. Previous color box 10 7 7. Lab values 1 8. CMYK values 9. RGB values 10. HSB values 9 11. Decreased 8 brightness

11

To access the available spot color systems (see Figure 3.14), click the Custom button to display the Custom Colors dialog box.

Exercise 3.8 The Relationship between Color Models In this exercise, you will open the Color Picker dialog box, specify a color using the RGB model, then observe the values assigned to the color in the other color models.

1. Double-click a Foreground Color Selection Box (either on the Tool palette or on the Color palette). 2. Enter the following values in the RGB fields: • R:255 • G:255 • B:0 3. Notice that the Color Slider is automatically moved to the yellow portion of the spectrum and that various tints, shades, and chromas of yellow are displayed in the Color Field (Figure 3.18). Also notice: 168 | C HAPTER THREE||

• The circle in the Color Field indicates that the specified color is a pure hue. • Yellow appears in the New Color box. • An exclamation point next to the New Color box alerts you that the specified color is outside the CMYK gamut. • The specified color’s equivalent HSB values are approximately H:60°, S:100%, B:100%. • The specified color’s equivalent Lab values are approximately L:97, a:-20, b:88. • The specified color’s equivalent CMYK values are approximately C:0, M:0, Y:94, K:0. 1 Figure 3.18 The completed Color Picker dialog box

1. The Closest CMYK Equivalent Box

4. Click the Closest CMYK Equivalent Box (see Figure 3.18). 5. Notice the following: • The exclamation point next to the New Color box has disappeared because the new color is within the CMYK gamut. • The new color’s equivalent HSB values are approximately H:55°, S:100%, B:100%. • The new color’s equivalent RGB values are approximately: R:255, G:234, B:0. • The new color’s equivalent Lab values are approximately L:95, a:-12, b:87. || Color Models | 169

• The new color’s equivalent CMYK values are approximately C:0, M:0, Y:94, K:0. These values are the same as before you clicked the Closest CMYK Equivalent Box because Photoshop adjusted the other color models to match the CMYK values. 6. Click OK to close the Color Picker dialog box. Notice that the newly specified color appears in both Foreground Selection Boxes.

Exercise 3.9 Specifying a Spot Color In this exercise, you will open the Color Picker dialog box, specify a spot color using the Custom Colors dialog box, and observe the values assigned to the color in the other color models.

1. Double-click a Foreground Color Selection Box (either on the Tool palette or on the Color palette). The Color Picker dialog box appears. 2. Click the Custom button. The Custom Colors dialog box appears. 3. Press the Book pop-up menu, then choose Pantone Uncoated. 4. Type “164”. The numbers you type appear in the field next to Key # (Figure 3.19)

The color identified as PANTONE 164 is displayed in a frame on the screen.

Figure 3.19 The Custom Colors dialog box

1. Frame indicates selected color 1 170 | C HAPTER THREE||

5. Click Picker. The Custom Colors dialog box disappears and the Color Picker is displayed. 6. Notice the following:

• The PANTONE 164’S equivalent HSB values are approximately H:10°, S:80%, B:100%. • The new color’s equivalent RGB values are approximately R:255, G:84, B:50. • The new color’s equivalent Lab values are L:68, a:58, b:54 • The new color’s equivalent CMYK values are C:0, M:47, Y:76, K:0. • There is no exclamation point next to the New Color Box. PANTONE 164 is within the CMYK gamut if reproduced using CMYK inks. 7. Click OK. The Color Picker dialog box closes. 8. Move the pointer over the Foreground Color Selection Box on the Color palette. Notice that the Color Tab on the Color/Swatches/Brushes palette now reads PANTONE 164 CV.

Color Display Modes

Photoshop uses several color modes to display, print, and store colors. Some color modes have the same names as color models, including the familiar RGB, CMYK, and L*a*b models. Other modes include Bitmap, Grayscale, Duotone, Indexed Color, and Multichannel. A brief description of each mode follows.

RGB Mode RGB is the color mode used by video displays, computers, and desktop scanners. This mode should only be used by graphic professionals as an intermediate step between scanning and CMYK conversion or to prepare images that will be viewed on a computer, television screen, or recorded onto color film. RGB images are usually 24-bit images that || Color Models | 171

contain more than sixteen million colors ranging from black to white. You can convert an image displayed in any color mode to RGB by choosing RGB Color from the Mode submenu of the Image menu. RGB images can be saved in all file formats available in Photoshop except CompuServe GIF and Filmstrip.

CMYK Mode CMYK is the color mode required to reproduce color photographs using printing presses and color proofers and printers. Because almost all color photographs for print media eventually must be converted to CMYK, convert RGB images to CMYK as soon as possible and build all colors to be used in process color documents using the CMYK model. An image displayed in any color mode can be converted to CMYK by choosing CMYK Color from the Mode submenu of the Image menu. CMYK images can be saved in Photoshop’s native formats, Photoshop EPS, JPEG, PDF, Raw, Scitex CT, and TIFF. There is disagreement among graphics professionals as to the best time to convert an image from RGB to CMYK. For example, the 4.0 User Guide recommends working on color images in RGB and converting to CMYK at the very end of the process. Their reasons include: 1) RGB files are smaller than CMYK files and, as a result, require less computer RAM and processing time; and 2) multiple conversions between CMYK and other color modes degenerate images due to the rounding of color values when they are converted from one mode to another. However, the same guide states “If you are concerned about precise CMYK values, or if you want to adjust the CMYK plate (images) directly, you may still perform your color corrections in CMYK.” Your authors prefer to convert to CMYK early in the process and agree with Adobe’s latter statement. To perform precise color targeting and correction, you must have access to the individual CMYK channels in the Levels and Curves dialog boxes. This need overrides any convenience that might accrue due to the smaller size of RGB files. It is true, however, that to prevent color degradation you should not convert back and forth from RGB to CMYK multiple times.

Lab Color Mode The Lab color mode is seldom directly used by printing and publishing professionals. However, Photoshop uses the L*a*b color model to convert 172 | C HAPTER THREE||

a color image in one mode to another mode. You may find it useful to convert an image to Lab mode so that you can adjust the lightness of an image without changing its colors. You will use the Lab mode in this way in Chapter 5. Lab mode is also useful when transferring color images from one type of computer system to another. Lab color files can only be saved in Photoshop’s native format, Photoshop EPS, Raw, and TIFF files.

Grayscale Mode Grayscale is the mode used when working with black-and-white photographs. An original photograph can be scanned as a grayscale image. In such a case, Photoshop opens the image in the grayscale mode. Color photographs can be converted to grayscale (simply display an RGB or CMYK image on the screen and choose Grayscale from the Mode submenu of the Image menu). Most grayscale images are 8-bit images and contain 256 ranging from white to black. However, Photoshop can also work with 16-bit grayscale images that contain 65,536 shades of gray. To convert a grayscale image from 8-bit to 16-bit, display an 8-bit image then, from the Mode menu, choose 16 Bits/Channel. Sixteen-bit images consume approximately twice the disk space as 8-bit images. Grayscale images can be saved in most file formats.

Bitmapped Mode Whereas grayscale images contain 256 shades of gray, bitmapped images only contain two shades—black and white. Bitmapped images are usually line drawings, such as maps or cartoons, that contain only solid color or blank areas and no shades. Photoshop can manipulate drawings originally scanned as or convert a grayscale image to line art. Grayscale images converted to line art are useful as special effects. A grayscale image can be converted to line art by displaying a grayscale image on the screen, then choosing Bitmapped from the Mode submenu of the Image menu. Bitmapped images can be saved in all Photoshop’s available file formats except Filmstrip, JPEG, PDF, Pixar, Raw, Scitex CT, and Targa.

Duotone Mode

■ duotone A duotone is a two-or-more color reproduction of a single color original. are often used to add color to a black-and-white photograph. For example, if a client has several color photographs and || Color Models | 173

one black-and-white photograph to include in a process color pamphlet, the black-and-white photograph would look out of place among the color photographs. Transforming the black-and-white photograph into an orange and black duotone would give the photograph some color and help it blend in with the color photographs. Another use of duotones would be to add some color to photographs that appear in a publication printed with only two colors of ink. For example, a company newsletter could be reproduced in only two colors—red and black—rather than CMYK. In such a case, CMYK inks are not being used, so photographs cannot be printed in process color. Instead, they are generally printed in black ink only. Transforming black-and-white into red and black duotones can add a special flair to the newsletter for virtually no additional cost. ■ tritone Duotones can also be produced with more than two colors of ink. A ■ quadtone tritone is a three color reproduction of a single color original, while a ■ monotone quadtone is composed of four colors. Monotones are grayscale images printed with a single, nonblack ink. An image can be converted to a duotone by first displaying it as a grayscale image, then choosing Duotone from the Mode submenu of the Image menu. You will be presented with the Duotone Options dialog box (see Figure 3.23) to make choices regarding the colors and type of color mixture you want for the image. In particular, you can choose to create a Monotone, Duotone, Tritone, or Quadtone, the colors to be used, and the amount of each color to apply. Duotones can only be saved in Photoshop’s native formats, EPS, or Raw format.

Printing Duotones with Spot or Process Color Duotones can be printed with either spot color or four-color process. For example, the two-color newsletter described above uses red spot color. The red color is made by mixing pigments into the ink to create the exact color desired by the customer rather than by overlapping percentages of yellow and magenta. In the case of the newsletter, creating the red color by using four-color process inks would be wasteful because printing the job using process color would require four press runs (C, M, Y, and K). Duotones printed in this newsletter should be composed of only two colors—red and black, so only two press runs will be necessary. If you create a red and black spot color duotone in Photoshop, two separate images will be output: one for red and one for black. Printing 174 | C HAPTER THREE||

technicians will use the two images to prepare the two printing plates needed to print the job. In the case of the color pamphlet that contains a black-and-white photograph transformed into an orange-and-black duotone, printing the duotone with a spot color would require five press runs (cyan, magenta, yellow, and black for the process color photographs plus orange for the duotone). In this case, running the duotone with a spot color would be wasteful. So, the orange color can be simulated using various sizes of halftone dots of the process color inks.

Choosing a PANTONE Color for a Duotone

If a duotone contains one or more PANTONE colors, the PANTONE colors can be simulated using the PANTONE PROSIM palette. Colors chosen from the PROSIM palette are all within the CMYK gamut. If you build a duotone using PROSIM colors, Photoshop will still consider the image to be a spot color duotone—two separate images will be output: one for each color in the duotone. To simulate colors in a duotone using CMYK inks, you must convert the duotone image to the CMYK mode before outputting the image. If you create a spot color duotone in Photoshop using the PANTONE PROSIM palette, then convert the duotone to the CMYK mode, four separate images will be output: one each for cyan, magenta, yellow, and black. Printing technicians will use the four images to prepare the four printing plates needed to print the job. The overlap of the cyan, magenta, yellow, and black inks will simulate the colors in the duotone. Duotones converted to CMYK can be saved in any file format that supports CMYK images.

Indexed Color Mode Indexed color images consist of only one channel of information rather than three (Lab and RGB) or four (CMYK) and can contain no more than 256 colors. For these reasons, the files are very small. Small file size can be very important if the final use of the image will be in a multimedia presentation. However, Indexed Color images cannot be printed with a printing press—they must first be converted to CMYK. Unfortunately, after converting an Indexed Color image to CMYK, the CMYK image will contain only the 256 colors that existed in the Indexed Color file. || Color Models | 175

NOTE To convert an image to Indexed Color, display a color image, then Indexed Color has no choose Indexed Color from the Mode submenu of the Image menu. You place in print media. will be presented with the Indexed Color dialog box that is used to make However, Indexed Color decisions regarding the type of conversion you would like made. You is very useful when preparing color images can save Indexed Colors in only a few selected file formats, including for electronic media. For Photoshop, BMP, CompuServe GIF, Photoshop EPS, PICT, PICT this reason, it will be discussed and used in Resource, PNG, Raw, Targa, and TIFF. Chapter 9. Multichannel When an image composed of more than one channel is displayed on the screen and you choose Multichannel from the Mode submenu of the Image menu, Photoshop changes the names of the channels to numbers and converts each channel to a separate grayscale image. This process is useful when converting a color image to black-and-white or for creating special effects. Multichannel images can only be saved in Photoshop and Raw file formats.

Exercise 3.10 Converting an RGB Image to Lab In this exercise, you will open an RGB file then convert the image to Lab.

1. From the File menu, choose Open. 2. Navigate to the Photoshop Student Files folder, then open the C3exercise2.eps ( C3exer2.eps) file. Click OK when the locked file message appears. 3. From the Image menu, choose Duplicate. Accept the defaults in the Duplicate Image dialog box, then click OK. A duplicate of the original image appears. If necessary, click the title bar of the duplicate to make it active. 4. From the Image menu, choose Mode, then select Lab Color. In a few seconds, the image is converted to Lab. Notice the changes in the title bar and in the Channels palette (Figure 3.20). 176 | C HAPTER THREE||

Figure 3.20 1 2 An image displayed in Lab mode

1. The original file is in the RGB Mode. 2. The copy is in the Lab Mode. 3. The channels palette displays the Lightness, a, and b Channels.

3

5. On the Channels palette, click the Lightness channel icon or use the keyboard shortcut + . Notice that the highlighting disappears behind the other icons and the image on the screen is composed of only black and white. The title bar changes to reflect the name of the channel that is displayed. The Lightness channel indicates the relative densities of each area of the image on the screen. Each area has a different halftone dot value to indicate the relative darkness of the area. These values can be read in the Halftone Dot Percentage field (which is not displayed at this time), or the K field of the CMYK section of the Info palette. Note: The Lightness channel is a black-and-white image, so the halftone dot values are indicated in the K field. 6. From the Image menu, choose Adjust, then select Levels from the submenu. The Levels dialog box appears. 7. Click the Preview option to select it. || Color Models | 177

NOTE 8. Move the Gamma input slider to the left until the Gamma input Changes made in the field reads about 1.40 to lighten the midtones. Then click OK. Levels dialog box affect You are making the change so that you will be able to see the impact only the Channel that was previously selected of adjusting only the Lightness channel of an image. in the Channels palette. In this case, moving the 9. On the Channels palette, click the Lab icon or use the keyboard Gamma input slider shortcut + ~ . affects only the Lightness channel  On the Channels palette, click the Lab icon or use the keyboard because that is the shortcut + ~ . only channel that was selected in the 10. Drag the title bar of the copy down so that you can see both the Channels palette. original RGB file and the L*a*b copy (Figure 3.21). Notice that the L*a*b version is now much lighter than the RGB version but the colors have not changed. This occurred because you adjusted the Lightness channel without altering either of the color channels.

Figure 3.21 Effect of adjusting the Gamma Input Level of the Lightness Channel 2 1. The Lab image appears lighter than the RGB image because the Lightness Channel gamma was adjusted. 1 2. The Color/Swatches/ Brushes Close Box.

11. On the Channels palette, click the “a” channel icon or use the keyboard shortcut + . Notice that the image is only composed of various and green. 178 | C HAPTER THREE||

12. On the Channels palette, click the “b” channel icon or use the keyboard shortcut + . Notice that the image is only composed of various and blue. 13. Close the duplicate image without saving any changes.

Exercise 3.11 Converting an RGB Image to Grayscale In this exercise, you will convert an RGB file to grayscale using two different methods.

1. Make sure the original RGB file is active. If necessary, click its title bar to make it active. 2. From the Image menu, choose Duplicate. Accept the defaults in the Duplicate Image dialog box, then click OK. If necessary, click the title bar of the duplicate to make it active. 3. From the Image menu, choose Mode, then select Grayscale. A message appears asking if it is OK to discard the color information. Click OK. In a few seconds, the image appears as a black-and-white photograph. Notice that the image appears rather flat (it has a short tonal range) and lifeless. Color photographs converted to black-and-white usually appear flat and dull. Sometimes, a better black-and-white halftone can be made by using one of the color channels of an RGB or CMYK image rather than converting the entire photograph to grayscale. The Multichannel model can facilitate this process. 4. Make the original RGB file active by clicking its title bar. 5. From the Image menu, choose Duplicate. Accept the defaults, then click OK. 6. Make sure the new copy is active (click its title bar if necessary). Then from the Image menu, choose Mode, then select Multichannel. Notice that the image appears black-and-white and that the three channels that existed in the RGB file are still listed on the Channels palette but their names have been changed from RGB to #1, #2, and #3, respectively. || Color Models | 179

7. Click each channel’s icon in turn. Look at the individual images on the screen. Notice that the image in Channel 1 is brighter and has more than the image in either Channel 2 or Channel 3. 8. Close the Color/Swatches/Brushes palette by clicking its Close box. 9. Arrange the screen so that the Grayscale image (the first copy) and the Multichannel image (the second copy) are both visible by dragging the document windows around on the screen using their title bars (Figure 3.22). Notice that Channel 1 of the Multichannel image is a better looking grayscale image than the actual grayscale image. Channel #1 contains more contrast and is brighter than the grayscale image. Notice particularly the difference in the second hat from the left in both versions.

Figure 3.22 A Grayscale image and a Multichannel image displayed on the screen

1. Notice the difference in the shades of these two hats. 2. The Channels palette menu triangle. 1 2

After a particular channel of a Multichannel image has been chosen as an acceptable grayscale image, the remaining channels must be deleted. To delete a channel from a Multichannel image, click the icon of the channel you wish to erase, then use the Channels palette menu to delete the unwanted channel. 180 | C HAPTER THREE||

10. Click the Channel #2 icon in the Channels palette. 11. Press the Channels palette menu triangle (see Figure 3.22 for its location), then choose Delete Channel. Channel 2 is deleted. 12. Repeat Steps 10 and 11 to delete Channel 3. 13. From the Image menu, choose Mode, then select Grayscale. The Multichannel image is converted to a Grayscale image. 14. Close both the first and second copies of the C3exercise2.eps ( C3exer2.eps) file (both grayscale images). Do not save the changes to either file.

Exercise 3.12 Converting an RGB Image to a PANTONE Spot Color Duotone In this exercise, you will convert an RGB file to grayscale then create an orange and black duotone. This duotone will be designed to be printed with two colors of ink—PANTONE 159 and black. 1. Make sure the original RGB file is active. If necessary, click its title bar to make it active. 2. From the Image menu, choose Duplicate. Accept the defaults in the Duplicate Image dialog box, then click OK. 3. Make sure the copy of the original file is active by clicking, if necessary, the title bar of the copy. 4. From the Image menu, choose Mode, then select Grayscale. A message appears asking if it is OK to discard the color information. Click OK. 5. From the Image menu, choose Mode, then select Duotone. The Duotone Options dialog box appears (Figure 3.23). || Color Models | 181

Figure 3.23 1 2 3 4 The Duotones Options dialog box

1. Input-output curve 2. Type pop-up menu 3. Color selection box 4. Color name field

6. Press the Type pop-up menu, then choose Duotone.

7. Click Load. Navigate to the PANTONE® Duotones folder (Figure 3.24). If your version of Photoshop has been installed normally, you should find the PANTONE® Duotones folder as follows: Adobe Photoshop 4.0⇒Goodies⇒Duotone Presets⇒Duotones⇒PANTONE® Duotones. If you cannot find the correct folder, see your instructor, trainer, supervisor, or lab assistant for help.  Click Load. Navigate to the Pms folder (Adobe/Photoshop/Duotones/ Duotone/Pms). If you cannot find the correct folder, see your instructor, trainer, supervisor, or lab assistant for help.

The PANTONE® Duotones folder contains a number of common combinations of PANTONE spot colors and black.

Remember that the PANTONE colors displayed on the screen are simulations of the actual printed PANTONE colors. A printed book, called the Pantone Color and Black Selector, displays how an actual combination of a PANTONE color and black will look when printed. 182 | C HAPTER THREE||

Figure 3.24 1 2 3 4 Some of the PANTONE® Duotone combinations

1. PANTONE® MATCHING SYSTEM color number 2. Name of color 3. Second color is black 4. Four variations of this

8. Click 159 dk orange bl 2, then click Open.  Click 159-2.ado, then click Open. The name means that this is a combination of a dark orange (PANTONE 159) and black. There are four combinations of these two colors available, and this is the second. The Duotone Options dialog box changes to reflect the changes you have made. In particular, the two chosen colors (Black and PANTONE 159 CV) appear as well as the curves that will be used to apply those colors to the image (more about curves in Chapter 6). (Note: The CV suffix after the PANTONE 159 name refers to Computer Version.) 9. Click OK. The grayscale image is converted to a duotone image composed of dark orange and black. Look at the Channels palette. Notice that a Duotone has only one channel. The duotone will be printed using two spot colors of ink. Two separations will be made by the output device: PANTONE 159 and black. These separations will be used to make two different printing plates that will be printed individually—one with PANTONE 159 CV ink and the other with black ink. 10. Close the duotone image. Do not save the changes. || Color Models | 183

Exercise 3.13 Converting an RGB Image to a PANTONE PROSIM Duotone In this exercise, you will convert an RGB file to grayscale, then create an orange and black duotone. This duotone will be designed to print using percentages of CMYK inks that will simulate PANTONE 159 ink. This procedure should be used whenever you want to print a duotone on the same page as four-color process photographs printed using CMYK inks. Simulating PANTONE color with CMYK inks prevents the need for a separate press run for the PANTONE ink.

1. Make sure the original RGB file is active. If necessary, click its title bar to make it active. 2. From the Image menu, choose Duplicate. Accept the defaults in the Duplicate Image dialog box, then click OK. 3. Make sure the duplicate of the original file is active by clicking, if necessary, the title bar of the copy. 4. From the Image menu, choose Mode, then select Grayscale. A message appears asking if it is OK to discard the color information. Click OK. 5. From the Image menu, choose Mode, then select Duotone. The Duotone Options dialog box appears. The Duotone Options dialog box should appear the same as it did when you closed it last time. 6. Click the Color Selection Box for Ink 2 (the orange color). The Custom Colors dialog box appears (Figure 3.25). 184 | C HAPTER THREE||

Figure 3.25 1 The Custom Colors dialog box

1. The Book pop-up menu. 2. The frame indicates this color is selected.

2

7. Press the Book pop-up menu at the top of the dialog box, then select Pantone ProSim. PANTONE 1675 automatically selected.

PANTONE 1675 CV is the color closest to PANTONE 159 that can be reproduced using CMYK inks. 8. Click OK twice. The grayscale image is transformed into a duotone. Although the orange color in the duotone has been defined using PANTONE PROSIM, Photoshop still thinks the image is a duotone and will output it on two sheets: one for Black and the other for PANTONE 1675 CV. To simulate the PANTONE color using CMYK inks, you now must convert the Duotone image to CMYK using the Mode submenu of the Image menu. 9. From the Image menu, choose Mode, then select CMYK color. The duotone will now be printed using the four process colors. Four separations will be made by the output device: one each for cyan, magenta, yellow, and black. These separations will be used to make four different printing plates which will be printed individually— one with each process color—that, when combined, will result in a simulation of a PANTONE 159 and black duotone. 10. Quit Photoshop. When prompted, do not save the changes to either image. || Color Models | 185

Chapter Summary

In this chapter, color models and how colors are fashioned using the two most common models—additive (RGB) and subtractive (CMYK)— were introduced. You learned how colors are created by adding red, green, and blue light waves together and that light waves form the colors you see when you look at a television monitor or a computer screen. You learned how Photoshop displays additive color components in channels and how the channels can be combined to display mixtures of color. Paint, ink, and dyes do not behave like light. These colorants contain pigments that subtract light from the substrate on which they are placed. This subtractive system uses process colored pigments called cyan, magenta, and yellow (CMY) rather than red, green, and blue light to form additional colors. Process colors, when combined, are deficient in blue and green and, as a result, blues and will appear dark and muddy when reproduced using process inks. These deficiencies cause many colors that you can see in real life and on your computer monitor to be out-of-gamut when reproduced using CMY. You discovered that overlapped layers of CMY cannot produce a dark black, so black ink is used to cover those areas resulting in the need to print each image four times (CMYK). Photoshop uses a number of different color modes to store and display images on the screen. You learned about the uses of each color mode, how to convert images from one mode to another, and the consequences when images are converted to the CMYK mode. Finally, you learned about the uses for some less prevalent color modes, including L*a*b, Indexed Color, Multichannel, and Duotone. 186 | C HAPTER THREE||

True/False Questions Self- Evaluation ____ 1. An apple is not really red, it just reflects red light. Review ____ 2. When adding waves of light, yellow contains both red and Questions blue. ____ 3. Every RGB color has an exact CMYK equivalent. ____ 4. The paper on which a color reproduction is printed makes a big difference in the perceived color. ____ 5. Bitmapped images contain 256 shades of gray.

Multiple-Choice Questions 6. Which waves of light must be added to create yellow light? A. red plus green B. red plus blue C. green plus blue D. magenta plus green 7. Which color of light is subtracted when a layer of magenta ink is printed on white paper? A. red B. green C. blue D. cyan 8. What color would appear if red and green inks are overprinted on paper? A. yellow B. whichever color is printed last C. whichever color is printed first D. black 9. Which of these colors look worst when printed using CMYK inks? A. yellow B. red C. magenta D. blue || Color Models | 187

10. In which of these color modes can you control the lightness or darkness of a color image without changing the colors? A. RGB B. CMYK C. Indexed Color D. Lab

Fill-in-the-Blank Questions 11. Humans see colors that are ______from, ______through, or ______by an object. 12. Any time you combine two or more sources of light energy, the result will always be ______than any of the individual component colors. 13. Process color inks are best printed on what color paper? ______14. Which color temperature of light source is recommended for viewing color prints or proofs? ______15. A ______is a two or more color reproduction of a single color original.

Short 1. Opening an RGB Image and Converting It to CMYK Projects 1. Prepare a new disk or folder. Name it ShortProjectsC3. 2. Open the file named ShortProjectC3. ( Spc3.tif) found in the Photoshop Student Files folder. 3. From the File menu, choose Save As. Save the file as ShortProjectRGB.tiff ( ShrtRGB.tif) on your ShortProjectsC3 disk or folder. Select ( ) Macintosh Order or () IBM PC Byte Order and LZW compression in the TIFF Options dialog box. 4. From the View menu, choose Gamut Warning. The colors in the RGB file that are outside the CMYK gamut are shown in gray. Turn off the Gamut Warning option by selecting it from the View menu again. 188 | C HAPTER THREE||

5. From the Image menu, choose Duplicate. Accept the defaults and click OK. 6. Be sure the copy is active. Then, from the Image menu, choose Mode, then select CMYK Color. The file is converted from RGB to CMYK. 7. Compare the RGB image with the CMYK image. Notice that the colors that turned gray when you chose Gamut Warning in Step 4 appear more muted in the CMYK version than in the RGB version. 8. Inspect each of the channels individually by clicking on the appropriate icon in the Channels palette. 9. From the File menu, choose Save As. Name the file ShortProjectCMYK.tiff ( ShrtCMYK.tif) and save it on your ShortProjectsC3 disk or folder. Select ( ) Macintosh Byte Order or () IBM PC Byte Order and LZW compression in the TIFF Options dialog box. 10. Close ShortProjectCMYK.tiff ( ShrtCMYK.tif).

2. Converting an RGB Image to Lab Mode 1. Be sure the original RGB image is active. Click on the title bar, if necessary. 2. From the Image menu, choose Duplicate. Accept the defaults and click OK. 3. Be sure the copy is active. Then, from the Image menu, choose Mode, then select Lab Color. The file is converted from RGB to Lab color. 4. Compare the RGB image with the Lab image. The two images should look identical because the gamut of the L*a*b model encompasses the entire RGB gamut. 5. Inspect each of the channels individually by clicking on the appropriate icon in the Channels palette. 6. Select the Lightness Channel by clicking on its icon in the Channels palette. || Color Models | 189

7. From the Image menu, choose Adjust and then select Levels. 8. Move the Gamma input slider until the Gamma input field reads about 1.26. Click OK. 9. Turn on all the channels by clicking the Lab icon in the Channels palette. Compare the Lab image to the original RGB image. Notice that the overall photograph is lighter but the colors remain the same. This happened because you changed the Lightness Channel without changing the color channels. 10. From the File menu, choose Save As. When prompted, name the file ShortProjectLab.tiff (ShrtLAB.tif) and save it on your ShortProjectsC3 disk or folder. Select ( ) Macintosh Byte Order or () IBM PC Byte Order and LZW compression in the TIFF Options dialog box. 11. Close ShortProjectLab.tiff (ShrtLAB.tif).

3. Converting an RGB Image to Grayscale 1. Be sure the original RGB image is active. Click on the title bar, if necessary. 2. From the Image menu, choose Duplicate. Accept the defaults and click OK. 3. Be sure the copy is active. Then, from the Image menu, choose Mode, then select Grayscale. The file is converted from RGB to grayscale. 4. Make the original RGB image active by clicking on its title bar. 5. From the Image menu, choose Duplicate. Accept the defaults and click OK. 6. Be sure the copy is active. Then, from the Image menu, choose Mode, then select Multichannel. The file is converted from RGB to Multichannel. 7. Inspect each of the three channels in the Multichannel image and compare each one to the grayscale image. Decide which of the four images (the grayscale image or one of the Multichannel images) would make the best looking black-and-white halftone. 190 | C HAPTER THREE||

If you select the grayscale image as the best looking, close the Multichannel image without saving the file. If you select one of the Multichannel channels, close the grayscale image without saving it. Make sure the Multichannel image is active. Then delete the channels you do not want to use for the black-and-white halftone. Now, from the Mode menu, choose Grayscale to convert the Multichannel image into a grayscale image. 8. Make sure your grayscale image is active. Then, from the File menu, choose Save As. When prompted, name the file ShortProjectBW.tiff ( ShrtBW.tif) and save it on your ShortProjectsC3 disk or folder. Select ( ) Macintosh Byte Order or () IBM PC Byte Order and LZW compression in the TIFF Options dialog box.

4. Converting a Grayscale Image to a Spot Color Duotone 1. Be sure the ShortProjectBW.tiff image is active. Click on the title bar, if necessary. 2. From the Image menu, choose Duplicate. Accept the defaults and click OK. 3. Be sure the copy is active. Then, from the Image menu, choose Mode, then select Duotone. The Duotone Options dialog box appears.

4. Click Load. Navigate to the PANTONE® Duotones folder. If your version of Photoshop has been installed normally, you should find the PANTONE® Duotones folder as follows: Photoshop 4.0⇒Goodies⇒Duotone Presets⇒Duotones⇒ PANTONE® Duotones. If you cannot find the correct folder, see your instructor, trainer, supervisor, or lab assistant for help. 5. Select 327 (50%) bl 1, then click Open. 6. Click OK on the Duotone Options dialog box. The image appears as an aqua and black duotone. || Color Models | 191

7. Make sure your duotone image is active. Then, from the File menu, choose Save As. When prompted, name the file ShortProjectDuo.eps ( ShrtDUO.tif), choose Photoshop EPS from the Format pop-up menu, and save the file on your ShortProjectsC3 disk or folder. Accept the EPS Format dialog box default settings. 8. Close ShortProjectDuo.eps and all other images that are still open.

Demonstrating Color Models Suppose you have a client who wants you to create a presentation that demonstrates how the same image can be displayed on the computer monitor using different color models. Further assume that you are provided with the file InDepthProjectC3.tiff ( Idprojc3.tif), found in the Photoshop Student Files folder, and that the file is the appropriate size for on-screen viewing. The client wants you to demonstrate the In-Depth appearance of an RGB image, a CMYK image, a L*a*b image, a Project Grayscale image, and a Duotone image on the screen. Each of these images must be saved as a separate EPS file on a single disk.

Use the following procedures as guidelines: 1. Prepare a new disk or folder and name it In Depth 3. 2. Open the InDepthProjectC3.tiff ( Idprojc3.tif) file, found in the Photoshop Student Files folder. 3. The file is already an RGB file, but it needs some improvement before you save it as your final RGB file. 4. Duplicate the RGB file, then convert the copy to Lab. 5. Select the Lightness Channel, then open the Levels dialog box. Click Auto, then move the Input Gamma slider until the Input Gamma field reads about 1.41. Click OK. 6. Save the file as InDepthProjectLab.eps ( IdLAB.eps) on your In Depth 3 disk or folder. Accept the defaults in the EPS Format dialog box. 192 | C HAPTER THREE||

7. Convert the image to RGB, then save the file as InDepthProjectRGB.eps ( IdRGB.eps) on your In Depth 3 disk or folder. Accept the defaults in the EPS Format dialog box. 8. Choose Gamut Warning from the View menu. The gray areas indicate the colors that are outside the CMYK gamut. 9. Convert the image to CMYK, then save it as InDepthProjectCMYK.eps ( IdCMYK.eps) on your In Depth 3 disk or folder. Accept the defaults in the EPS Format dialog box. 10. Be sure the CMYK image is active, then Duplicate the image. 11. Convert the copy to grayscale. 12. Make the CMYK image active by clicking on its title bar. 13. Duplicate the CMYK image, then convert it to RGB. 14. Convert the RGB image to Multichannel. 15. Inspect each of the three channels in the Multichannel image. Determine if you would prefer to use any of the individual channels as a black-and-white photograph instead of the grayscale image. If you like the grayscale image best, close the Multichannel file without saving it. If you like one of the channels of the Multichannel file best, delete the other channels, and convert the remaining channel to grayscale. 16. Save your chosen grayscale image as InDepthProjectBW.eps ( IdBW.eps) on your In Depth 3 disk or folder. Accept the defaults in the EPS Format dialog box. 17. Convert the InDepthProjectBW.eps ( IdBW.eps) image to a duotone. Choose any combination found in the PANTONE® Duotones folder. If, after viewing the image on the screen, you do not like the color combination, simply choose Duotone from the Mode submenu of the Image menu again and load a different duotone combination from the PANTONE® Duotones folder. 18. Save your finished duotone image as InDepthProjectDuo.eps ( IdDUO.eps) on your In Depth 3 disk or folder. Accept the defaults in the EPS Format dialog box. 19. Close any open files and quit Photoshop.