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Understanding Color Management for Printers 12/15/11

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Understanding Color Management for Printers 12/15/11 Understanding Color Management for Printers 12/15/11 Understanding Color Management 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 Gamut / Color Space / Color Model - - - - - - - - - - - - - - - - - - - - - - - - 6 Rendering Intents - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7 Ink 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 + Green =Yellow. Red + Blue = Magenta. Magenta +Yellow = Red. Magenta + Cyan = Blue. R = Red G= Green C = Cyan B = Blue M = Magenta Y = Yellow K = Black Green + Blue = Cyan. Yellow + Cyan = Green. Red + Green + Blue = White Cyan + Magenta + Yellow = Black RGB coloring mixes light to make different colors. RGB is an additive system (adds light to make color) CMYK coloring mixes pigments 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. White Point: 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 photography. 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 spot color 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 inks 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 printer 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)
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