Quick viewing(Text Mode)

Color Management Basics 35 Color Management 02Basics

Color Management Basics 35 Color Management 02Basics

34 Management in Practice

Setting up the equipment and environment needed for has never been easier. Most promising is the release of the EIZO ColorEdge series of Adobe RGB-compatible LCD monitors, designed for superb color management. Ideally, monitors offering high-precision color reproduction allow users to match the displayed and printed. In fact, the creation of color reproduction standards, a major development in recent years, has benefited both the printing and advertising industries. Print workflows rely on color proofing; now, Japan Color, JMPA colors, and other standards can serve as guidelines in establishing workflows. JMPA colors in particular make it possible to replace conventional proofing with DDCP or to use inkjet printers instead of presses for proofing. No extra work; simply specify JMPA profiles before output. Those involved know what to expect right from the start, when the original ad has been completed on-screen. Comparing images on ColorEdge monitors to documents printed with JMPA profiles brings you closer to a perfect match between monitor and proof colors. This requires expert knowledge of software and hardware, and this book can shed some on the subject. The first step is to try it and see. W.W. Abney. A TREATISE ON , 1918

©iStockphoto.com/wsfurlan © DWH Co., LTD. Color Management Basics 35 Color Management 02Basics

©iStockphoto.com/Hello Vector!

©iStockphoto.com/wsfurlan 36

Maxwell also established the visible to us. Newton’s original Light radiation, Wavelengths fundamental principle that light classifications of , , , reflection, absorption, travels in waves, and his research , , , and are too and color in light on electricity and magnetism led general for work in this context. and transmission to the development of the unified As for wavelengths we cannot Light can be described by its Combining red, green, and blue light to model of electromagnetism. Today, see (shorter than 380 nm or longer than 780 wavelength, which determines its produce was a famous feat by James both phenomena are identified as nm), scientists knew that these waves color in the spectrum. Two factors Clerk Maxwell (1831–1879) in lectures at manifestations of electromagnetic existed even before Maxwell's time. affect the wavelength of light: King's College in London in 1861, where he force. Maxwell showed that light is Sir Frederick William Herschel radiation and absorption. demonstrated the world's first color photo. a form of energy we can describe as discovered infrared radiation, with Maxwell also explored how we perceive visible an electromagnetic wave and that wavelengths longer than 780 nm, in Radiation of light: light in the . wavelengths of visible light lie in the 1800. This was followed in 1801 by When another form of energy In the 20th century, as we began to range of 380–780 nm (with one million a discovery at the opposite end of the is converted to light energy, light understand how insects and many other nanometers in a millimeter). spectrum by Johann Wilhelm Ritter, radiates from the energy source. This creatures are physically equipped to perceive One consequence is that shorter who identified ultraviolet radiation radiation is generated by chemical phenomena, researchers in animal behavior wavelengths of light are refracted with wavelengths shorter than 380 nm. or physical processes, such as the found that various creatures perceive various more sharply. Research on the Maxwell correctly concluded that burning or heating or cooling of wavelengths of light. What we perceive as spectrum since Newton has made the electromagnetic waves exist at atoms or molecules. It is worth color, for example, is the specific range of it possible to assign values to these wavelengths, but that our eyes noting here that the definition of the spectrum that the particular RGB-sensing the spectral wavelengths that are simply cannot perceive them. “white” light varies. system of our eyes reveals to us.

icEne edicin ision adar dcast ic Gene m rg M e V R oa in tr ra to y r g c t le o A B r E

wavelength(1nm=10-4m) ultraviolet rays infrared rays

human being

butterfly

deep-sea

Each animal species perceives color differently. monkey Animals are equipped with what we may regard / fowl as unique optical instruments. The particular biological hardware of one species lets it perceive fish different wavelengths of light than another snake species. In each case, perception results from long-term evolutionary changes to promote 300 340 survival in various environments. ultraviolet rays infrared rays Color Management Basics 37

Light absorption and reflection: Spectral data and For objects that radiate light, For transmissive objects as well, Absorption is the opposite of spectral curves radiance can be measured and transmissivity can be measured and radiation, occurring when light charted. Radiance is the relative charted. Transmissivity is the ratio energy is converted into another Objects can be broadly classified intensity of light energy radiated at of incident light to transmitted light form of energy, when the atoms or into three categories based on how various wavelengths, based on the at each wavelength. In the chart, green molecules of an object or medium they interact with light. In each case, total amount of light energy. In the indicates the transmissivity of ink. struck by light absorb the light. spectral curves show how objects chart, yellow indicates the spectral A colorimeter can be used to How much light of the various affect light of various wavelengths. curve for , with the diagonal measure the spectral data of any wavelengths is absorbed depends on The following chart shows examples line indicating values for an ordinary object and derive spectral curves. the chemical structure of the object of several spectral curves. incandescent () bulb. Thus, spectral data provides a or medium. Interactions between Similarly, reflectivity can be detailed record of the amount of wavelengths and the structure of ① Radiant objects (such as daylight measured and charted for objects light reflected at each wavelength, the object cause light to be reflected or monitors) that reflect light. Reflectivity is the something that cannot be confirmed from or absorbed into the surface. ② Reflective objects or objects that ratio of incident light to reflected by sight alone. Measurements of this Thus, reflections can also be viewed absorb light light at each wavelength. In the chart, kind require an instrument called a as radiation occurring after light is ③ Transmissive objects indicates the reflectivity of spectrophotometer. partly absorbed. red objects.

Transmission of light: 100 Ancient scholars puzzled over Daylight spectra the nature of clear materials and the (%) light passing through such materials. Reflectivity of a red object Their confusion arose from a 80 misunderstanding—that color was Transmissivity of cyan ink inherent in the surface of things. ower ① Radiant objects Light passing through clear or al P Incandescent (tungsten) bulb semitransparent substances such as 60 water, air, film, or ink is transmitted through the substance. This occurs ② Reflective objects/ light-absorbing objects when more of some wavelengths Relative Spectr 40 of light are absorbed than others as they strike molecules and particles in a substance. The thickness of a particular object determines the 20 Monitor (red ) extent to which various wavelengths are absorbed or passed. Only a vacuum fully transmits light of all ③ Transmissive objects 0 wavelengths.

400 500 600 700 wavelengths(nm) 38

Color rendering defined The suitcoat and pants that appeared The following figure shows to match at the store somehow clash colors affected by metamerism and Publications that discuss at a party. Or the bouquet of flowers colors that maintain a consistent and color rendering color often address favorable that looked beautiful at the florist appearance. These three products or unfavorable color rendering looks dull and lifeless under your appear identical under natural properties, but the underlying at home. There are countless , but incandescent lighting concept of color rendering is rarely examples. brings out a reddish tinge in two defined. It is worthy of initial We can reverse the underlying of them. Of course, we can also consideration, since this is a key issue principle applying in all these cases imagine the opposite effect. in the context of metamerism. to create color with a consistent As for ensuring consistent Color rendering is the effect of appearance by combining multiple colors through the data used in the color of the light source on the color components. For example, photographic prints or printing, appearance of color in objects. This instead of creating gray from newer inkjet printers can reduce the characteristic is known as the light and white as usual, we can effects of metamerism, but a D50 or source’s color rendering property. create the same color by mixing D65 light source is recommended The is one way complementary such as red and for post-printing proofing. Use the to compare relative performance in blue-green, yellow and bluish , isochromatic samples at the end of this regard. or blue and orange. this book.

Metamerism Three requirements are essential in perceiving color: light, objects, and our eyes. Metamerism occurs when these elements are out of sync from their normal relationship. The phenomenon can make two colors

that appeared identical under one With metamerism light source look different under another. Our eyes are susceptible to metamerism, but in fact, the phenomenon also affects other instruments that operate on principles of RGB light mixing, such as scanners and digital . Realistic examples are often cited in explanations of metamerism. Buy fresh fish that looks delicious at the deli, and you may lose your appetite when you see the colors With metamerism Without metamerism under fluorescent lighting at home. ©iStockphoto.com/CreativeLogicConsulting Color Management Basics 39

Color tinge. The color remains blue even at those with a at 5000 K higher . This is because have a yellowish tinge. In general, is a scale the additional wavelengths emitted at this system of notation is only used to distinguish colors of light. these temperatures are too short to be approximate. Of the many radiant Color temperature is measured in seen. light sources that exist, none perfectly Temperature White Light Source of Light Balance (a unit of absolute temperature), and Next, a system of notation was matches the characteristics of a black values are followed by the symbol devised to describe radiant light body. Strictly speaking, descriptions 10,000 K Clear blue sky K. Color temperature is expressed sources relative to a . of color temperature are thus the relative to black-body radiation, Measurements were made to correlated color temperatures. The as described below. Although the determine the spectral distribution of system of notation also applies only and sky appear to change color various light sources. These put light to radiant objects. It cannot be 9,000 K between sunrise and , we can bulbs at 2800 K and sunlight at 6500 applied to reflective or transmissive express a constant color in terms of K, and people characterized colors at objects, since the black body model temperature relative to black-body various levels. Computer monitors approximates the molecular process radiation. As a scale for expressing and televisions have specific white of radiation in objects that emit light. 8,000 K the color of light, color temperature points that affect other colors. For was first proposed by British example, monitors with a white point physicist William Thomson (Lord at 9300 K have a bluish tinge, while 7,000 K Kelvin). Clouded sky A more detailed explanation will clarify these ideas. Because Relationship of color temperature to the Fluorescent or strobe lighting molecules release energy in the spectral distribution in light sources 6,000 K form of light as objects cool, all Noon sunlight objects emit light when heated. In HMI Metal vapour this context, the theoretical concept 5,000 K of a black-body, as proposed in 1859 by Gustav Robert Kirchhoff, 9,000 K is useful. This ideal object reflects and transmits no light whatsoever. 4,000 K Because all wavelengths of light are 7,000 K fully absorbed, all light emitted is in 6,000 K Tungsten the form of . Since we can calculate wave- 5,000 K 3,000 K Relative Spectrum Power lengths in black-body radiation, we 4,000 K know that the change in spectral 3,000 K curves is constant (as demonstrated by Max 2,000 K 2,000 K light Planck in 1900) and can be predicted. A black body glows red at 2400 K and yellow at 5000 K. At 6500 K, it turns 500 600 700 white; at 9300 K, it takes on a blue 400

Wavelengths(nm) Guide to Agfa 40

CIE The historic CIE meeting took place Discovery of tristimulus Color-matching experiment in September 1931 in Cambridge, by color perception RGB, the dominant coincidence the city where Newton How can we verify this basis for in digital imaging, is not necessarily had published Optics. This marked , who postulated our sense of color experimentally? ideal for color management. the first international attempt to retinal RGB receptors, observed The environment shown below Everything you rely on in pro- establish a system for observing that many colors can be created is used to demonstrate how we duction, from your eyes to devices and measuring color under specific from the three primary colors of perceive color and derive the ratio such as scanners, monitors, and conditions of illumination and red, green, and blue. These theories of constituent colors that match a printers, covers a slightly different observation. were later refined by Hermann reference color. Subjects compare the RGB . In other words, there is The 1931 CIE system defined von Helmholtz, who presented colors of the top and bottom halves ① (the field of a different range of colors between a standard observer spectral curves for each color. In of a circle seen through a hole in view for observing colors) ② red, green, and blue for each device. ; standard practice, it is useful to understand a screen and respond to questions (light sources) ③ Fortunately, the values representing illuminants ; the CIE that tristimulus principles form the on the perceived colors. Behind ④ colors on one device can be XYZ set of tristimulus values; and basis for describing individual colors the screen are the two sources of (in reference to a color space converted relatively easily into Yxy notation as combinations of three primary these colors: a trio of red, green, and and diagram), among other (the three primary colors, to those for other devices. No other colors (such as RGB) and for deriving blue lamps system shows special matters. HSB and similar color models. test the tristimulus theory of color perception) promise as a standard color space Through many refinements, this across from a reference light source. for typical applications. However, system was improved in the ensuing RGB levels are adjusted until the other colors do in fact lie outside years. In 1964, the definition of the subject feels the top and bottom the RGB triangle. For this reason, standard observer was refined. 1976 (R) halves match. This demonstrates the International Commission on saw the addition of ① perceptually tristimulus color perception and Illumination (CIE) has devised a uniform color spaces called CIE (G) makes it possible for us to derive the new international tristimulus color LAB and CIE LUV ( L*a*b* a n d corresponding ratio of red, green, system, envisioned as the master L*u*v*, respectively), ② a method for (B) and blue. system for all other color spaces. quantifying how "close" two colors vHelmholtz's sketh of estimated spctral sennsitivity of three fundamental processes.( 1860) The most reliable color spaces are (in the form of ΔE*), and other are therefore based on this XYZ guidelines. CIE later developed (Δ E2000) color space developed by CIE. the ΔE00 color-difference F Target Color Photographers and designers rarely equation and defined the wide work with CIE XYZ directly, but sRGB gamut for digital cameras, White Screen Masking Screen color experts must know about this among many other achievements. Test Light F system, which is used internally The organization remains a leading when computer software handles authority, setting trends in color color, and in other applications. specifications. CIE hoped to establish an Red, green, and essential shared point of reference blue light levels are Primary Light R+G+B adjusted until the for manufacturers of paint, dye, observer perceives the ink, textiles, and so on, used, for top and bottom colors B as matching. example, when specifying product G Primary v The Color-Matching Experiment colors. R Color Management Basics 41

CIE standard observer identified after measurement with a technology enabled researchers to relatively perceptually uniformity, wider than 2°, and the gauge this subtle discrepancy, and in such as CIE LAB and CIE LUV. CIE color measurements clearly data was reexamined. This problem 1964, CIE added the supplementary The value is called the ΔE* (Delta require a controlled environment was especially pronounced for the standard observer (based on measurements E) or , and a color in several basic respects. First are range of colors from blue to green. from a 10° field of view) to account for difference equation is used to requirements regarding the observer. Again, anatomical considerations fields of view wider than 4°. A calculate this value. Of these two To determine the definition of a arose. The is an area new notation was introduced to color spaces, CIE LAB is often used “normal” observer, data was gathered at the center of the in which distinguish between these 2° and 10° in professional settings. as several subjects peered into the more cones than rods are found. But fields of view: X10Y10X10. However, Determining the distance color-matching equipment. even within a field of view wider in the absence of indications to between two colors involves plotting The 1931 definition of a standard than 4°, which includes an area the contrary, a 2° observer is still their coordinates, then measuring observer specifies a 2° field of view without many cones, color can be assumed. the distance—i.e., color difference— for measurement, since most cone discerned. between the two points. cells (color-sensitive photoreceptors) are Only slight discrepancies were ΔE* and color difference In the case of CIE LAB, the color concentrated at the center of the noted between color as perceived difference between the two colors retina. This remains a common from these different fields of view, is expressed as ΔE*ab, which is To calculate how “close” two standard even today. rarely rising to discernible levels. calculated as follows: colors are, we use color spaces with 2 2 1/2 In 1964, discrepancies were But advances in measurement ΔE*ab = (ΔL* + Δa* + b*2) . However, this is easier to understand if we describe the practical significance of some color difference values. Generalizations are as follows: ΔE*ab = 0.5… The difference is nearly imperceptible. ΔE*ab = 1.0 …A very slight difference can be seen. ΔE*ab = 2.0 …The color difference

1.7 ㎝ is clear when one color is placed 8.8 ㎝ over the other, but the colors look identical when two small samples are compared. A tolerance level of around ΔE*ab = 6 is common in typical printing applications. However, values around ΔE*ab = 6 are significant given the performance of current equipment, so an approximate value of ΔE*ab = 3 may be preferred in the printing 50 ㎝ industry. 42

Basic Terminology composition, black (K) is usually added to RAW Data: RGB: the other colors. The less cyan, magenta, An image format in SLR cameras. A model used to produce colors from You may encounter a variety of unfamiliar terms and yellow are used, the more red, green, Although JPEG files offer both additive of the three in the context of color management. Some terms and blue are apparent. Thus, CMY can be convenience and smaller file sizes, typical primaries of light—red, green, and blue. are defined as they are introduced in this book. interpreted as a special application of the SLR cameras can save files in a proprietary Color is produced in the RGB model for Here we provide a basic reference glossary. RGB model. (See Fig. 1) RAW data format. The term RAW derives equipment that uses color in a way that CMY(K): CMM: from the fact that data is saved nearly resembles tristimulus color perception. A model used to produce colors from An abbreviation of color matching unchanged from the raw information Our eyes and all devices such as scanners mixing of the three module or method. As one component captured by the CCD. Since RAW data and monitors use a particular set of RGB primaries of cyan, magenta, and yellow. of a color management system, CMMs is not subjected to image processing to colors that differ slightly from others. Unlike mixing, in which use profile information, describing device refine sharpness, white balance, or other In other words, there are as many RGB the three primaries are added to black, characteristics, for color conversion from the parameters, professional photographers formats as there are devices. Describing color is produced in the CMY model by color space of one device to that of another. generally save in RAW format, then use colors in the RGB model thus requires subtracting particular wavelengths from Profiles are device- or tool-dependent, and image editing software to achieve the identification of the specific device. white. This model is used in printing. To individual profiles utilize the CMM of the desired effects. overcome limitations associated with ink same manufacturer or developer.

Visible Light 0.8 Cyan Red RGB monitor gamut B

0.6 CMYK-based Magenta Green gamut S H 0.4 γ= 1

0.2 Yellow Blue

0 Fig. 1 Fig. 2 0 0.2 0.4 0.6 Fig. 3 Fig. 4

RGB Workflow: which more ink in intermediate colors sRGB: management for equipment such as Although images or graphics files are is required. Here, special profiles must Standard color space, established as computer peripherals. Data established traditionally converted into CMYK be used in color separation to avoid a specification by the International by the ICC regarding device-specific format before submission for printing, problems. Electrotechnical Commission (IEC) in color reproduction characteristics (written RGB workflows have emerged in the past HSB: October 1998. sRGB covers a slightly in conformance with color reproduction standards) are few years. With RGB workflows, after A that describes color not as narrower gamut than color spaces such as called ICC profiles. approval from the printing company, a combination of primary colors but as a Adobe RGB, and the gamut is restricted in Illuminant: images and layout files are submitted combination of the three attributes of , certain areas, including hues of emerald Formal definitions of an illuminant are in the RGB format used by the saturation, and brightness. Based on the green and cyan and hues of orange, bright difficult to understand, and they may photographers and designers involved, Munsell system, HSB separates the color- red, and yellow. For this reason, sRGB refer to a mathematical description of and an optimal conversion method is related attributes of hue and saturation may be considered less than optimal for the relative spectral power distribution of then applied by the printer. People are from the attribute of brightness (also called photography, graphic design, or other light sources. For our purposes, consider moving to RGB workflows in part due to or the Munsell value), which is unrelated professional applications, although it an illuminant equivalent to a light source. the many problems that have emerged at to color. As a special case of the HSB generally presents no problems for general In practice, there are several “standard the design stage from CMYK conversion model, the Munsell system is perceptually use. illuminants” (A–F). The specific one chosen of perfectly captured . RGB uniform. The HSB model is also generally ICC Profile: varies with the application or country workflows are desirable when using somewhat more intuitive than the RGB The International Color Consortium of use. The most familiar is probably wide-gamut ink such as Kaleido, for model. (See Fig. 2) (ICC) establishes specifications on color illuminant D. Illuminant D50 and D65 are Color Management Basics 43

the recommended light sources for color ColorNavigator after connecting the color devices have a particular value, while adjusting brightness so that the management. viewer to a ColorEdge monitor. (See p. 71.) and accurate image reproduction requires darkest part matches the black of the Color Viewer: Gamut: an overall gamma of 1, accounting for all monitor edge, outside the scanning lines. Color viewers are dedicated display units The range of colors that can be repro- devices used from initial image input to Of course, white level and contrast must used to evaluate colors after printing. duced. The of common devices final output. (See Fig. 4) be adjusted thereafter. Many formats are available, ranging such as monitors and printers can be Example: Using a scanner with a gamma Color System: from small units used by designers and compared—for example—by plotting of 0.45 and a monitor with a gamma of 2.2 According to JIS Z 8105-1982: a series photographers to large units sold with them on an xy chromaticity diagram. yields an overall gamma of 1. of definitions (using particular symbols), and printing presses. Although few Japanese (See Fig. 3) Page 30 provides a detailed Black Level Adjustment: the system formed by these definitions, models have been produced in recent illustration of gamuts. Adjusting a monitor so that the darkest intended for precise color matching. years, the color viewers mentioned in Gamma: image displayed (black) is rendered Systems applying to the sequence of this book (marketed by German-based JUST or A value that expresses the relationship accurately as black. Monitor calibrators colors standardized by the International U.S.-based GTI) are popular models. Using of image input to output. For example, are normally used, but if no calibrator Colour Association (AIC) are called color JUST color viewers for color proofing a gamma of 1.0 would yield a straight is available, a image created in order systems. Color order systems were on EIZO monitors, viewers can adjust line at a 45° angle for equivalent input Photoshop with about 20 intermediate classified by the late color scientist Deane color viewer brightness and intensity in and output when shown on a graph. All steps from white to black can be displayed Judd of AIC as (1) systems combining

E=klogI+C 100

80

60

40

Sensation Intensity (E) 20

0 0 20 40 60 80 100 Fig. 5 Physical Intensity (I) Fig. 6 ©EPSON Fig. 7 Fig. 8 colorants, (2) color mixing systems, (3) of equipment color characteristics. Profiles Metamerism: Fechner discovered a critical relationship color appearance systems, and between (1) created through characterization are A phenomenon whereby two colors between sensation and stimulus. and (2), color charts for printing systems. sometimes available from manufacturers. match under a particular light source An example of this relationship is Color Inconstancy: Calibration: but not under a different light source. apparent in the fact that even if the Color appearance varies with changes Calibration involves measuring the Similarly, under a different light source, actual brightness of a light source is in the color temperature of the light display or output of a particular device, colors that originally appeared different doubled, the increase in brightness is not source. The appearance of and determining any variance from a may appear identical. Taking this necessarily perceived to have doubled. photographic works on display depends predetermined standard, and adjusting phenomenon into consideration, we Sensation is not proportional to the greatly on the color of the illumination. the device to eliminate the discrepancy. recommend a color viewer with a D50 or quantity of physical stimulus. This (manufactured by New inkjet printer ink Standards used in calibration are either D65 standard light source when proofing relationship is illustrated in the chart. Epson) reduces such color inconstancies. average values derived from several units on monitors, from printed documents, or We now understand that as stimulus Attempting to reduce the effect of light through characterization or universal in printing environments. (For details, see p. 38.) increases, the intensity of sensation sources is, in effect, the opposite of standards. Afterward, a profile to Fechner's Law: traces a curved path that gradually metamerism. (See Fig. 7) compensate for the measured discrepancy Law proposed by German scholar Gustav attenuates. This is known as Fechner's Characterization: with the standard is applied to RGB values Theodor Fechner (1801–1887), a pioneer in law, a key concept in color systems, Calculating average values for the same created by or transmitted to the device. the field of psychophysics, which explores which quantify color. (See Fig. 8) devices made by a particular manufacturer. the relationship between sensation and Characterization enables approximation stimulus. 44

Precautions for indoor color is viewed under sunlight are lighting for color evaluation with optimal. But since the nature of a color rendering index of AAA In Practice lighting sunlight varies depending on the would be desirable. Additionally, weather, time of day, orientation, equipment for viewing the materials Determining illumination is season, and location, standard of interest (original photos and printed the first step in introducing a color lighting conditions are determined documents) in isolation under ideal management system. Lighting is the by ISO specifications. D50 lighting lighting is available from suppliers of First, critical factor for accurate viewing conditions are considered optimal design and platemaking equipment. of color in originals and in the for printing. Create an environment These are sometimes identified results as displayed on monitors or that will bring you as close to D50 as as “color viewers.” For design and build an prints. This requires some thought possible. Keep the following points performance reasons, models from even in closed environments, where in mind. U.S.-based GTI or German-based environment the entire workflow up to the final JUST are recommended. quality check is performed at a Choosing the right for assessing single location. By coordinating light source Precautions related all conditions in the color-viewing color environment, you can ensure that to the brightness of all off-site tasks (at the offices of clients, As the D50 light source, create an indoor illumination designers, and platemakers and printers at environment in which the entire 100 z for various times) are performed under indoor space and the materials color evaluation Once the indoor illumination to be viewed (original photos and (an AAA color identical80 conditions, allowing you is ready, seek the optimal viewing rendering index) printed results) are illuminated by to build an environment that’s arrangement for original photos fluorescent lighting designed for reliable60 for substituting color data and printed documents so that color evaluation. A variety of these in DTP or in remote proofing. only these materials are under the 40 specialized lamps are available, and The ideal indoor lighting environ- D50 light source while conditions z A portable viewer ment serves as the basis for meeting leading manufacturers offer them from JUST in surrounding areas resemble

Specific energy (%) 20 designed to the same specifications. Normlicht of the requirements for a variety of a . By simulating a Germany For example, N-EDL fluorescent colors. Environments in which darkroom, you can keep light 0 380 400 500 600 700 780 reflected from external sources from Wavelengths (nm) affecting color evaluations. However, 100 100 Color Rendering A typical white given the difficulties imposed fluorescent light Your monitors, printers, and Index AAA-type by working under darkroom 80 daylight color 80 similar equipment will fulfill the conditions, as a practical alternative,

main role when you introduce a 60 60 consider ways to reduce indoor color management system. But illumination to the extent feasible. One approach might be to use fewer don't forget the environment 40 40 fluorescent tubes where multiple

used to assess color. Here, the key Specific energy (%)

20 Specific energy (%) 20 lamps are installed. elements are indoor illumination If possible, use fluorescent lighting 0 0 with louvers to reduce from and your choice of monitors. 380 400 500 600 700 780 380 400 500 600 700 780 monitors. Wavelengths (nm) Wavelengths (nm) 100 ©iStockphoto.com/Night And Day Images

80

60

40

Specific energy (%) 20

0 380 400 500 600 700 780 Wavelengths (nm) Color Management In Practice 45

Precautions regarding temperature values, so that the two the colors of furniture color patches match most closely under a D50 light source. (General and walls guidelines are as follows. For D50 lighting, a

ΔE of 1.01; for D65 lighting, a ΔE of about 1.27; Even if you dim the lights, and for three-band fluorescent lamps at a color brightly colored furniture or walls temperature near D50, a ΔE of about 1.61.) may reflect significant ambient light, Try using the card to check light or light may enter from windows, sources. Note that the performance mixing with the colors under of fluorescent tubes will change over examination, preventing accurate time, so they should be replaced at assessments. Ideally, choose relatively regular intervals. dark furniture and use thick curtains to block external light or take similar measures. These decisions should Monitor selection probably be made on a case-by-case criteria basis, since imposing rigid working conditions may ultimately hinder The monitor is the most import- productivity. ant device in a color management system. Ideally, the colors displayed Confirm correct lighting on the monitor will simply flow conditions from step to step throughout the entire process down through You may want reassurance printing. For this reason, a monitor that the environment you have that can reproduce color accurately carefully arranged is optimal by is essential. Until a few years ago, switching to fluorescent lighting CRT monitors were the most and taking other measures. You commonly deployed; LCD monitors can check illumination using the were regarded as lacking the color color temperature meters used by accuracy required for desktop photographers and other imaging publishing and similar tasks. But the professionals. Measure the color emergence of the ColorEdge series temperature of monitor surfaces completely transforms this state and color proofing environments. of affairs. Since the release of the ColorEdge CG220, LCD monitors D50 lighting should register at about 4900 – 5100 K to provide the desired have become the main-stream for environment. One alternative to printing and design use. expensive color temperature meters is the Simple Metamerism Sample in Appendix B. The card has been printed to account for specific color ©Durupa 46

Monitor selection reveals that the curves are not linear, shipment to compensate for from indoor lighting when working criteria which explains why some image variations between individual LCD under conditions not resembling areas appear washed out. In contrast, panels. a darkroom, we recommend using When selecting the monitor right the ColorEdge series (except for the a monitor hood or darkroom for you, your key criteria should CG19) has 16-bit internal processing Monitor viewing curtains. The ColorEdge series include the number of display colors for solid performance rivaling CRT environment comes with a monitor hood as a and their display stability. ColorEdge monitors. Support for the Adobe standard accessory (optional with the monitors support calibration. While RGB color space with the ColorEdge Once your indoor environment CG19 and CG232W). DIY monitor hoods more mainstream LCD monitors CG221 makes it an especially good and monitors are ready, prepare may be used, but always apply a can also be calibrated, making them choice from the standpoint of the monitor viewing environment non-reflective material such as black more viable choices for applications display colors. itself. Remember that indoor light velvet to the inner surfaces. involving color management, To guarantee uniform per- and other factors can cause glare measuring the actual gamma curves formance, each ColorEdge monitor on glass monitor screens and subtly of conventional LCD monitors is measured and tuned before affect contrast. To prevent glare

16-bit prossesing 10-bit prossesing Error Percentage Error Percentage

Gradation [0–255] Gradation [0–255] v The gamma values of each ColorEdge unit are v A ColorEdge series hood optimized before shipping. v Conversion differences between 16- and 10- bit processing: 10-bit processing generates more conversion errors, particularly in darker areas; 16- bit processing (with ColorEdge monitors except the CG19) results in more precise conversion.

Monitor adjustment solutions. This method offers the by clicking to indicate the desired a good idea to recalibrate monitors most accurate adjustment and values. It also allows easy profile after moving them or changing The last requirement to management, but requires dedicated creation. indoor illumination. ensure faithful color reproduction equipment. The other approach is is adjustment — specifically, to use monitor adjustment software Calibration intervals calibration. Broadly speaking, bundled with other applications or there are two methods of monitor operating systems, such as Adobe Monitors must be calibrated calibration. One approach is to use Photoshop (using Adobe Gamma) and Mac regularly. Calibration software such a combination of hardware (in the OS X (using ColorSync). (Note: Adobe Gamma as ColorNavigator Agent (p. 71) can form of calibrators or spectrophotometers) is not supported by Mac OS X.) This method automatically notify you when it is and dedicated software, as in i1 lets users make adjustments simply time to perform calibration. It is also 47

JUST colorCommunicator × EIZO ColorNavigator www.just-normlicht.com

JUST colorCommunicator is the first viewing booth available worldwide that communicates with EIZO ColorNavigator monitor calbriation software tor precisely coordinate the on screen representation and the standardized light to each other. 48

As international specifications L*a*b* values when printing colors based proofing systems as part of Standard printing on color reproduction in printing, are reproduced on the monitor certification for proofing systems the ISO 12647 series specifies and measured. This certification capable of reproducing printing colors and basic printing characteristics program was launched in April colors in compliance with ISO soft-proofing and requirements for digital 2008. One requirement for monitors 12647. The criteria for monitors proofing. This has paved the way is screen uniformity. Proofing include (1) screen uniformity, for establishing and introducing systems are certified as supporting (2) monitor profile accuracy, (3) Soft-proofing is an approach that has become more widely known since last year, and interest is surging, standard printing colors in line with printing conditions corresponding accuracy of gradation characteristics, since it lets the user essentially preview on the regional needs: by Fogra in Europe, to GRACoL C1 and SWOP (4) gamut, and (5) viewing angle monitor how documents will appear after offset or SWOP and GRACoL in North C3 and C5. In the certification characteristics. inkjet printing. Actual deployment of equipment for America, and Japan Color in Japan. examination, all 1,617 patches of IT What makes the FograCert soft- soft-proofing is also taking off. The factor driving Printing characteristics, paper, and 8.7/4 are displayed and measured proofing system noteworthy is that this trend is the establishment of standard printing target CMYK patch values (L*a*b*) for evaluation, enabling objective the accuracy of monitor display practices designed for consistent quality and greater production efficiency. Updated certification programs have been tailored to particular judgment based on numerical colors is evaluated by examining for proofing systems (including monitor-based printing conditions and standard values. Display colors in the center color differences relative to a master proofing) are also earning industry support, as the ICC profiles provided, making it of monitor screens are measured, print, ensuring ample accuracy not certification organizations promote higher accuracy. easier to assemble digital proofing but to ensure accuracy across the just for checking color and color systems with inkjet printers and screen, the screen is measured while proofing at the prepress stage, but monitors. As a result, soft-proofing displaying the three levels of white, also in scenarios like viewing color is starting to take off in Europe and gray, and dark gray to check for samples on the monitor in printing North America. uneven colors and luminance. A environments. high level of uniformity is required IDEAlliance Monitor for certification. Japan Color Proofing Systems An EIZO soft-proofing system (comprising ColorEdge LCD monitors support- Standard printing colors and Certification ing color management as the display device and digital proofing, including soft- industry-standard Adobe Acrobat Professional proofing, have caught on in Japan Focusing on proofing (color sample) as the viewing software) has been certified somewhat later than in other systems for web offset printing, as a system enabling simulation of regions. Nevertheless, as with the SWOP certification program GRACoL C1 printing colors. This FograCert, the Japan Printing accepted IDEAlliance calibration is a good example of an affordable, Machinery Association (JPMA) has techniques and characterization low-maintenance, soft-proofing taken the initiative in establishing a in 2006. With the sheetfed offset system. certification program for businesses printing standards of GRACoL, and for processes that reproduce these standards have been updated printing colors conforming to Japan as certification for proofing systems FograCert Softproofing Color guidelines. JPMA is also applied to offset printing. Objective System looking to establish certification for evaluation methods were also Fogra, a German industry digital proofing systems. established for monitor-based soft- association, establishes and proofing systems, which determine conducts certification for monitor- any color difference from target

ISO 12647-7 Digital Control Strip 2009 3% A 100 60 100 70 30 100 60 100 70 30 100 60 100 70 30 100 40 40 100 40 100 40 70 40 70 40 40 40 70 40 40 70 40 70 40 40 3 10 25 50 75 90 100

B 100 100 60 100 100 70 70 30 30 100 100 60 100 100 70 70 30 30 100 100 60 100 100 70 70 30 30 100 40 100 40 40 100 10 40 40 20 70 70 70 70 40 70 40 40 0 0 0 0 3.1 2.2 2.2 10.2 7.4 7.4 25 19 19 50 40 40 75 66 66 100 100 100 80 70 70 100 Color Management In Practice 49

Windows Color System (WCS) is the CIE) is used as the basis for color monitors formerly used only in the Windows 's new color management management. graphic arts industry are becoming system, introduced in Windows Vista. A prominent example among popular as regular monitors and Color System WCS is positioned as a platform that the few applications that currently people use Office applications to (WCS) resolves issues with ICC profile-based support WCS is the Microsoft create and view business documents color management systems, although Office 2007 suite. Once Windows with images, demand exists for few applications using WCS have Vista color management settings correct monitor profiles specified been developed or launched to date, are correctly configured, images in device profiles and correct and the platform is not pervasive. with embedded color space profiles display colors reflecting sound color Among WCS’s distinguishing are correctly displayed based management. features, color conversion infor- on monitor color reproduction Additionally, printer drivers mation is kept separate from the information (in the monitor profile) for certain Canon printers can device profile as the basis of objective by Office 2007 programs. This is adjust printing colors to suit the measurement; a gamut-mapping in contrast to earlier versions of ambient light in the specific viewing model makes WCS more versatile Office applications, which process environment when printing business for color conversion; and CIE all RGB images as sRGB images. In graphics for presentation display. CAM02 (a ratified by environments where wide-gamut ©iStockphoto.com/S-E-R-G-O 50

The ecosystem of color management Principles in color management

In color document production, determined by rendering intent. One suited to photo printing and similar a match between monitor colors of four rendering intents is chosen applications. and printed colors matched without (perceptual, saturation, relative colorimetric, (Note: Preliminary investigations are advisable before creating workflows that rely on printer drive color management would be a and absolute colorimetric (p. 96)), depending settings. Manufacturers may change these settings remarkable coincidence. Usually, on the color matching goal. Note without notice.) color management is essential for that choosing the wrong rendering For application color management, coordinating colors among devices. intent may lead to poor results. For simply choose a profile for high Colors will not otherwise match since professional color management, start accuracy in the profile settings and the methods and materials used to by preparing ColorEdge monitors or disable color management in the reproduce color vary from device to others supporting calibration*( p . 4 3 ) driver. RIP color management is Color Scanner device. and a measuring instrument as slightly more sophisticated, but once Although our eyes may sometimes provided in X-Rite i1 solutions or the the principles are understood, this fool us into thinking that colors Datacolor Spyder series, then calibrate method can be quickly mastered. somehow match without color or characterize*(p.43) each device. Fortunately, while color settings management, measurements with Several workflows are conceivable across applications must be considered, color instruments generally reveal for color management involving Adobe Bridge in Adobe Creative Suite discrepancies. Whether they like it printed output, depending on the 4 makes it easy to coordinate a color or not, designers and photographers environment. These can be broadly environment comprised of multiple must learn color matching—or, more classified as either application applications. Color management is now specifically, color management. color management or RIP color less esoteric and much more familiar Color management can be management. Even in the production than it once was. Digital summarized by the relationships of this book, we distinguished between shown at right. ICC profiles, files that these approaches. Also available describe the color attributes of each are color adjustment functions device, are used to maintain the colors devised by printer manufacturers of the original across various devices and implemented in printer drivers. to the extent possible. (This is also called But since PostScript® files cannot be gamut mapping.) The parameters that examined (a prerequisite for most take priority when matching colors is printing), these functions are better ©iStockphoto.com/chuntise Color Management In Practice 51

Adobe RGB color space in soft-proofing

This refers to accurate colors choosing Adobe RGB as your shared Monitor throughout the entire workflow—in color space throughout the workflow, shooting, layout, and printing. This goal which may involve shooting with Adobe of color management, and the system to RGB-compatible digital cameras, achieve it, is fundamental to professional editing image data in production. Only with a complete color on Adobe RGB-compatible EIZO management system environment in ColorEdge monitors, and other steps place can you appreciate the benefits. before conversion to a CMYK format for An important first step is choosing a printing, you can arrange an effective common color space, which will serve as environment for color management, the unequivocal standard and prevent enabling soft-proofing with a higher needless cycles of color matching. By level of precision.

Inkjet Printer

Color Management in Adobe RGB

Prepress & Printing Design Photography

Adobe RGB Adobe RGB Adobe RGB

Process Print Layout Layout Check Data Shoot Image Masking, Compositing, Enlarging, Reducing, Printer Edit Adjustment Paths Soft proof instead of hard proof with DDCP’s and inkjet printers Printing Press Edit while simulating Edit Adobe RGB image No need for Photoshop CMYK color space ➞Soft proof color engine

By sharing a color space at each stage, the image will be rendered in the same way. 52

Color management Color management, does not draw on expertise with Color management the key to efficient DTP traditional processes, and ultimately, supports DDCP, CTP, LFP, in print workflows we must rely on the knowledge of advanced techniques of each and POD To understand the role of color individual involved. In many cases, Color management plays a greater role than ever, management in print workflows, Techniques such as direct digital as print workflows evolve. Here, we explore color frustrated designers and clients are management and its benefits. consider the stage of printing in the color proofing and computer-to- submitting material as they did context of DTP. Print workflows plate (DDCP and CTP) skip traditional before, including color samples or are becoming fully digital. Moving platemaking in several ways. In actual objects for reference. to digital print workflows has CTP, color DTP data is burned Digital color management simplified processes. Clients directly to aluminum plates from a is a different way of thinking, a and designers alike have more computer. CTP produces screens just comprehensive approach to color opportunities to deal directly with as on film, eliminating the step of from the initial stage through the printing data. The ability to traditional film-based platemaking. printing. Color management systems preview the final printing quality (This book was produced using CTP.) also account for differences among during prepress color DTP work Direct digital color proofers, a various environments (client, designer, paves the way to more efficient popular type of digital color proofer, prepress, and printer) and equipment, workflows and lower printing costs. take color proofing into the digital providing an environment that But some workplaces have yet to age. maintains a consistent appearance reach this stage. When the final Recent large-format inkjet for identical color data. Once the color data cannot be previewed as is printers (LFP) come with built-in color management system is in place normally expected during prepress color gauges for more consistent with the correct settings, you can or if it cannot be guaranteed under output. More businesses are using enjoy the benefits of simpler, more the current workflow, we often see these LFPs for proofing as part of efficient color DTP print processes. clients or designers compromising the color management process. Although moving to digital text and in color proofing of press samples. Models that provide additional digital layout information is also They accept discrepancies between support for new orange and green important, moving to digital color expected and actual colors. Or we ink are being used for proofing data to make it possible to achieve see subtle fine-tuning in prepress or with wide-gamut ink, such as Toyo the expected results after printing is at press, through corrections of the Kaleido Ink. If the stages of color critical. data submitted, ink adjustments, proofing and film proofing can be and so forth. Skill in these processes performed with color DTP data and ©iStockphoto.com/Liliboas Color Management In Practice 53 final print quality can be ensured, enhancing consistency in remote Wide-gamut printing with ink these steps can be omitted for proofing. like Toyo Kaleido Ink is gaining simpler, more efficient workflows. The EIZO ColorEdge series is an in popularity. The basics of color For this reason, businesses moving ideal monitor for color proofing. management are illustrated above; to CTP and other such technologies All RGB levels (0 – 255 for each color) are see p. 110 for detailed information should commit to a color factory-tuned for each monitor to on Kaleido Ink workflows. management system. ensure uniformity and exceptionally smooth gradations. Color Color management in management is easy, even in separate environments where several people print workflows are involved in remote proofing. Color management in print workflows enables consistent viewing of color data anytime Input Illustration Pagenation Print CTP and anywhere for modification, editing, or revisions. Toward this end, an environment for accurate color management must be created throughout the workflow. C ColorEdge can be instrumental in M this fundamental task of building Y K environments. As Adobe Creative Suite gains Profile Scanner Monitor A Monitor B Monitor C Printer Profile Profile Profile Profile Profile more powerful application color management features, even small- scale photographers and designers Printer Profile can set up color management environments with relative ease. In Japan, standards are in place Color Management System for the entire printing industry. Japan Color standards are used in commercial printing, Japan Color Proofing Printing JCN2002 for newspapers, and JMPA colors for advertisements.

Artwork created by John Ritter Artwork created by John Ritter Artwork created by John Ritter Artwork created by John Ritter Artwork created by John Ritter © 1993 Adobe Systems Incorporated. All rights reserved. Adobe Illustrator is a trademark © 1993 Adobe Systems Incorporated. All rights reserved. Adobe Illustrator is a trademark © 1993 Adobe Systems Incorporated. All rights reserved. Adobe Illustrator is a trademark © 1993 Adobe Systems Incorporated. All rights reserved. Adobe Illustrator is a trademark © 1993 Adobe Systems Incorporated. All rights reserved. Adobe Illustrator is a trademark of Adobe Systems Incorporated that may be registered in certain jurisdictions. Artwork may of Adobe Systems Incorporated that may be registered in certain jurisdictions. Artwork may of Adobe Systems Incorporated that may be registered in certain jurisdictions. Artwork may of Adobe Systems Incorporated that may be registered in certain jurisdictions. Artwork may of Adobe Systems Incorporated that may be registered in certain jurisdictions. Artwork may not be reproduced for commercial purposes. It is illegal to remove or modify this statement. not be reproduced for commercial purposes. It is illegal to remove or modify this statement. not be reproduced for commercial purposes. It is illegal to remove or modify this statement. not be reproduced for commercial purposes. It is illegal to remove or modify this statement. not be reproduced for commercial purposes. It is illegal to remove or modify this statement. For remote proofing environments, Epson's ColorBase printer calibration tool can be used to minimize variations between Epson inkjets. Recent models All alike at all points also feature built-in color gauges,