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Understanding Management for Printers 12/15/11

Understanding for Printers

Understanding Color Management for Printers 12/15/11 Table of Contents Understanding Color Management for Printers ------1 Table of Contents ------2 Color Concepts ------3 RGB / CMYK ------4 L*A*B* ------5 / / ------6 Rendering Intents ------7 Control ------11 Ink Restriction ------12 Ink Linearization ------15 Linearization ------17 Ink Limit (Combined Ink Restriction) ------18 Controlling Color ------19 ICC Profile ------20 Workflows ------23 Workflow (Photo with a RIP) ------24 Workflow (Photo with Epson Driver) ------25 Workflow (Proofing with a RIP) ------26 Workflow (Production with a RIP) ------27

Page 2. Understanding Color Management for Printers 12/15/11

Color Concepts Terms to Understand

Page 3. Understanding Color Management for Printers 12/15/11 RGB / CMYK

Red + =. + = . Magenta +Yellow = Red. Magenta + = Blue.

R = Red G= Green C = Cyan B = Blue M = Magenta Y = Yellow K =

Green + Blue = Cyan. Yellow + Cyan = Green. Red + Green + Blue = Cyan + Magenta + Yellow = Black RGB coloring mixes to make different . RGB is an additive system (adds light to make color) CMYK coloring mixes to make different colors. Pigments absorb some frequencies (colors) of light, and reflect the desired frequency (color). CMYK is a subtractive system (absorbs undesired, and reflects desired light to make color). RGB and CMYK are opposites of each other.

RGB / CMYK Page 4. Understanding Color Management for Printers 12/15/11 L*A*B*

L*A*B* values are device independent reference values. L*A*B* values can represent any color and brightness. L*A*B* values plot a color’s location in a 3 dimensional color space.

L* = Luminance (Brightness) L+ A* = Green to Red B* = Blue to Yellow B+

L* range = 0 (Dark) to 100 (Light) A* range = - Green to + Red B* range = - Blue to + Yellow A- A+

B-

L-

L*A*B* Page 5. Understanding Color Management for Printers 12/15/11 Gamut / Color Space / Color Model Color Space Gamut

Color Model

Color Model = RGB or CMYK Color Space = A theoretically defined range of colors within a color model (SRGB, Adobe RGB, etc.). Gamut = The actual range of colors that a device can reproduce.

Gamut / Color Space / Color Model Page 6. Understanding Color Management for Printers 12/15/11 Rendering Intents

Saturation

How It Works: Preserves the Saturation (color brightness) of colors. Out of Gamut Colors: will be moved to the closest fully saturated, in gamut color. In Gamut Colors: may be moved to the closest, more saturated colors. : will not be changed.

When To Use: Use when the exact relationship between colors is not as important as rendering bright colors. Use for charts and graphs.

Downside: No color accuracy.

Rendering Intents Page 7. Understanding Color Management for Printers 12/15/11

Perceptual

How It Works Compresses all colors proportionately to bring out of gamut colors into gamut. Preserves the visual relationship between colors. Out of Gamut Colors: the furthest out of gamut color will be moved to the edge of the destination gamut. The other out of gamut colors will be moved in the direction of the center of the gamut, to maintain the visual relationship between all colors. In Gamut Colors: will be moved in the direction of the center of the gamut to maintain the visual relationship between all colors. White Point: will not be changed.

When To Use: Use for . Use when color accuracy is not as important as image detail.

Downside: Less Contrast: Because the gamut will be compressed proportionally to handle out of gamut colors, the contrast between light and dark will also be reduced.

Rendering Intents Page 8. Understanding Color Management for Printers 12/15/11

Relative Colorimetric

How: Out of Gamut Colors: will be moved to the closest in gamut color. In Gamut Colors: will not be moved. White Point: will not be changed.

When: Use for photography or production Use when detail in the shadow areas is important Use when visual accuracy is more important than measurable accuracy.

Downside: Out of Gamut colors may not be visibly accurate. In Gamut colors may not measure accurately because the white point is not adjusted.

Rendering Intents Page 9. Understanding Color Management for Printers 12/15/11

Absolute Colorimetric

How: Out of Gamut Colors: will be moved to the closest in gamut color. In Gamut Colors: will not be moved. White Point: will be changed.

When: Use when measured color accuracy is more important than visual accuracy. Use when accuracy is important. Use for proofing

Downside: Although the colors may measure accurately, they may appear “shifted” because the white point is adjusted.

White Point adjusted to match destination. White Point not adjusted.

Rendering Intents Page 10. Understanding Color Management for Printers 12/15/11

Ink Control

Understanding Media Saturation and Ink

Page 11. Understanding Color Management for Printers 12/15/11 Ink Restriction Purpose: To determine the maximum amount of each ink that can be applied to the media and still increase gamut. In Other Words: For each ink, determine the maximum gamut with the least amount of ink. Fact: As saturation is approached, gamut increase rolls off. Fact: Applying Ink with no gamut increase causes problems with no benefit.

1. Print Target Patches

Target Patches CMYK 5% theoretical increase per patch From 5% to 100%

Ink Restriction Page 12. Understanding Color Management for Printers 12/15/11

2. Measure and Graph each patch with the Eye One SpectroPhotometer.

C = 75 M = 80 Y = 65

Determine the maximum amount of each CMY ink that can be applied to the media and still increase gamut.

Ink Restriction Page 13. Understanding Color Management for Printers 12/15/11

3. Register maximum patch for each color.

C = 75 M = 80 Y = 65

Ink Restriction Page 14. Understanding Color Management for Printers 12/15/11 Ink Linearization

Fact: The maximum amount of each ink that the media can accept is usually less than 100%. Fact: The percentage of each ink that the media can accept is determined by the Ink Restriction step. Purpose: The Ink Linearization step redefines the usable amount of ink to 100%, and evens out the gradient steps.

Simplified Explanation Using Cyan in as an example: 1. Maximum usable Cyan ink = 75%

2. Redefine 75% as 100% 3. Print new target using redefined levels (step 2)

4. Measure the 20 theoretical 5% gradient patches.

5. Compare the 20 theoretical 5% gradient patches with the 20 measured 5% gradient patches

6. Adjust the measured 5% gradients until they match the theoretical 5% gradients.

Fact: A 5% gradient change between 15% and 20% might require a 6% ink increase to produce an actual 5% gradient change. Fact: A 5% gradient change between 20% and 25% might require a 4% ink increase to produce an actual 5% gradient change.

Ink Linearization Page 15. Understanding Color Management for Printers 12/15/11

Ink Linearization

Measured patch values Theoretical (desired) patch values

Ink Linearization Page 16. Understanding Color Management for Printers 12/15/11 Linearization Measured patch values Linearization table (correction values)

+

Target patch (desired) values

=

Linearization Page 17. Understanding Color Management for Printers 12/15/11 Ink Limit (Combined Ink Restriction) Fact: Various combinations of react differently in terms of media saturation. Process: Various combinations of inks are printed at different saturation levels to determine the point that over satu- ration occurs. Purpose: Combined ink “over saturation” points are used to further restrict ink levels applied to the media.

Ink Limit Explanation 80 patches per row Ref # 0.05 Ref # 4.00

1. Print swatch 2. Inspect Swatch quickly and look for wet ink. Wet ink = “over saturation”.

Ink Limit (Combined Ink Restriction) Page 18. Understanding Color Management for Printers 12/15/11

Controlling Color ICC Profile

Page 19. Understanding Color Management for Printers 12/15/11 ICC Profile Note: A ICC Profile is used to accurately translate color data from L*A*B* to CMYK.

1. Print the Target

Note: A target consists of many color patches. Note: The more patches in a target, the more accurate the ICC Profile. Note: Each patch in a target represents a theoretical color. Note: All of the patches of theoretical colors are known as the Reference Data.

3 pages of an ICC profile target.

ICC Profile Page 20. Understanding Color Management for Printers 12/15/11

2. Read (Measure) the Target. Note: Reading the target is performed by a color measuring device. Note: The color measuring device in this example is an Eye One (SpectroPhotometer). Note: The color measuring device reads the actual color value for each patch. Note: All of the actual color values read by the Eye One are known as the Measured Data.

Eye One SpectroPhotometer

Each line of patches is scanned by the Eye One, in sequence, until all patches have been read.

ICC Profile Page 21. Understanding Color Management for Printers 12/15/11

3. Create the ICC Profile Note: In this example ProfileMaker 5.0 is being used to create the ICC Profile. Note: ProflieMaker 5.0 compares the Reference Data with the Measured Data. Note: The difference between the Reference Data and the Measured Data is used to create the ICC Profile. Note: A Printer ICC Profile is a list color inaccuracies inherent to the Printer. Note: A printer ICC Profile allows accurate translation from L*A*B* to CMYK by providing the color inaccuracy information inherent to the Printer. Note: A Printer ICC Profile is a table of color errors for a Printer.

Reference Data

Measured Data

ICC Profile Page 22. Understanding Color Management for Printers 12/15/11

Workflows For Production

For Proofing

For Photography

Page 23. Understanding Color Management for Printers 12/15/11 Workflow (Photo with a RIP) Note: A Photo workflow is used to produce visually accurate color on a digital printer. Measurably accurate color is not important Color Model: Source Image: RGB RGB to L*A*B* conversion: Input Profile: Controls the conversion of RGB to L*A*B* with no restriction of color gamut. Rendering Intent: Perceptual because it maintains the visual relationship between all colors (including out of gamut) but may loose detail in shadow areas. Relative Colorimetric because it maintains the visual relationship between all colors with no loss of details in shadow areas. Out of gamut colors may appear wrong. L*A*B* to CMYK conversion: Output Profile: Accurately controls the conversion of L*A*B* to CMYK. Rendering Intent: Perceptual because it maintains the visual relationship between all colors (including out of gamut) but may loose detail in shadow areas. Relative Colorimetric because it maintains the visual relationship between all colors with no loss of details in shadow areas. Out of gamut colors may appear wrong.

Media Saturation Control: RIP: controls Ink Limit, Linearization, and Ink Restriction.

Epson InkJet:

Workflow (Photo with a RIP) Page 24. Understanding Color Management for Printers 12/15/11 Workflow (Photo with Epson Driver) Note: A Photo workflow is used to produce visually accurate color on a digital printer. Measurably accurate color is not important Color Model: Source Image: RGB RGB to L*A*B* conversion: Working Space: Use embedded or assign a working space. Rendering Intent: Perceptual because it maintains the visual relationship between all colors (including out of gamut) but may loose detail in shadow areas. Relative Colorimetric because it maintains the visual relationship between all colors with no loss of details in shadow areas. Out of gamut colors may appear wrong. L*A*B* to CMYK conversion: Output Profile: Attach to an application (PhotoShop) to accurately control the con- version of L*A*B* to CMYK. Rendering Intent: Perceptual because it maintains the visual relationship between all colors (including out of gamut) but may loose detail in shadow areas. Relative Colorimetric because it maintains the visual relationship between all colors with no loss of details in shadow areas. Out of gamut colors may appear wrong. Media Saturation Control: Epson Driver: controls Ink Limit, Linearization, and Ink Restriction.

Epson InkJet:

Workflow (Photo with Epson Driver) Page 25. Understanding Color Management for Printers 12/15/11 Workflow (Proofing with a RIP) Note: A Proofing workflow is used to produce a sample of a “print job” before it is mass produced. Because it is intended to be used for “customer sign off”, it must look exactly like the “print job” that the mass production press will produce. The proofing workflow restricts the gamut of a wide gamut printer (Epson Inkjet) to emulate the output of a narrower gamut printer ( press). A proofing workflow must also be “color accurate” so that company specific colors (logos, etc.) are correct. Color Model: Source Image: CMYK

CMYK to L*A*B* conversion: Input Profile: Controls the conversion of CMYK to L*A*B* and restricts the Gamut to match a mass production press Rendering Intent = Absolute Colorimetric (no paper white compensation because there is no paper associated with this step).

L*A*B* to CMYK conversion: Output Profile: Accurately controls the conversion of L*A*B* to CMYK. Rendering Intent: Absolute Colorimetric with paper white compensation for visual and measured accuracy of colors.

Media Saturation Control: RIP: controls Ink Limit, Linearization, and Ink Restriction.

Epson InkJet:

Workflow (Proofing with a RIP) Page 26. Understanding Color Management for Printers 12/15/11 Workflow (Production with a RIP) Note: A Production workflow is used to mass produce “output” on a digital press. The printing must appear to be “color accurate” so that company specific colors (logos, etc.) look correct. Measurable color accuracy is important, but visual color accuracy is more important. Color Model: Source Image: CMYK

CMYK to L*A*B* conversion: Input Profile: Controls the conversion of CMYK to L*A*B* with no restriction of color gamut. Rendering Intent = Relative Colorimetric because it maintains the visual relationship between white and all colors.

L*A*B* to CMYK conversion: Output Profile: Accurately controls the conversion of L*A*B* to CMYK. Rendering Intent: Relative Colorimetric because it maintains the visual relationship between white and all colors.

Media Saturation Control: RIP: controls Ink Limit, Linearization, and Ink Restriction.

Epson InkJet:

Workflow (Production with a RIP) Page 27.