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

Understanding Color Management for Printers 12/15/11

Understanding Color Management for Printers


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Table of ContentsUnderstanding Color Management for Printers - - - - - - - - - - - - - - - - 1Table of Contents - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2Color Concepts - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3

RGB / CMYK - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4L*A*B* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5Gamut / Color Space / Color Model - - - - - - - - - - - - - - - - - - - - - - - - 6Rendering Intents - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7

Ink Control - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 11Ink Restriction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 12Ink Linearization - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 15Linearization - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 17Ink Limit (Combined Ink Restriction) - - - - - - - - - - - - - - - - - - - - - - 18

Controlling Color - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 19ICC Profile - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 20

Workflows - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 23Workflow (Photo with a RIP) - - - - - - - - - - - - - - - - - - - - - - - - - - - 24Workflow (Photo with Epson Driver) - - - - - - - - - - - - - - - - - - - - - - 25Workflow (Proofing with a RIP) - - - - - - - - - - - - - - - - - - - - - - - - - 26Workflow (Production with a RIP) - - - - - - - - - - - - - - - - - - - - - - - - 27


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Color ConceptsTerms to Understand


RGB / CMYK .

RGB / CMYK

C = CyanM = MagentaY = Yellow K = Black

R = RedG= GreenB = Blue

Cyan + Magenta + Yellow = BlackRed + Green + Blue = White

Magenta +Yellow = Red.

Red + Blue = Magenta.

Magenta + Cyan = Blue.

Yellow + Cyan = Green.Green + Blue = Cyan.

Red + Green =Yellow.

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.


L*A*B* .

L*A*B*

L+

L-

A- A+

B-

B+

L* = Luminance (Brightness)A* = Green to RedB* = Blue to Yellow

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

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.


Gamut / Color Space / Color Model .

Gamut / Color Space / Color Model

Color Model = RGB or CMYKColor 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.

Color Space Gamut

Color Model

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derstanding Color Management for Printers

ndering Intents

Rendering Intents

aturation

ow It Works:reserves the Saturation (color brightness) of colors. ut of Gamut Colors: will be moved to the closest fully saturated, in gamut color. Gamut Colors: may be moved to the closest, more saturated colors.hite Point: will not be changed.

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

ownside:o color accuracy.

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HCPO stination gamut. The other

he gamut, to maintain the

In visual relationship between

W

WUU

DLe mut colors, the contrast


ndering Intents

erceptual

ow It Worksompresses all colors proportionately to bring out of gamut colors into gamut.reserves the visual relationship between colors.ut of Gamut Colors: the furthest out of gamut color will be moved to the edge of the de

out of gamut colors will be moved in the direction of the center of tvisual relationship between all colors.

Gamut Colors: will be moved in the direction of the center of the gamut to maintain the all colors.

hite Point: will not be changed.

hen To Use:se for photography.se when color accuracy is not as important as image detail.

ownside:ss Contrast: Because the gamut will be compressed proportionally to handle out of ga

between light and dark will also be reduced.

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ndering Intents

elative Colorimetric

ow:ut of Gamut Colors: will be moved to the closest in gamut color. Gamut Colors: will not be moved.hite Point: will not be changed.

hen:se for photography or productionse when detail in the shadow areas is importantse when visual accuracy is more important than measurable accuracy.

ownside:ut of Gamut colors may not be visibly accurate. Gamut colors may not measure accurately because the white point is not adjusted.

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sted.


ndering Intents

bsolute Colorimetric

ow:ut of Gamut Colors: will be moved to the closest in gamut color. Gamut Colors: will not be moved.hite Point: will be changed.

hen:se when measured color accuracy is more important than visual accuracy.se when spot color accuracy is important.se for proofing

ownside:lthough the colors may measure accurately, they may appear “shifted” because the whit

White Point adjusted to match destination. White Point not adju


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Ink ControlUnderstanding Media Saturation and Ink

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Ink .

P a and still increase gamut.In k.FaFa

1.


Restriction

Ink Restrictionurpose: To determine the maximum amount of each ink that can be applied to the medi Other Words: For each ink, determine the maximum gamut with the least amount of inct: As saturation is approached, gamut increase rolls off.ct: Applying Ink with no gamut increase causes problems with no benefit.

Print Target Patches

Target PatchesCMYK 5% theoretical increase per patchFrom 5% to 100%

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Ink .

2.

75= 80 65

the maximum ach CMY ink

applied to the still increase


Restriction

Measure and Graph each patch with the Eye One SpectroPhotometer.

C =M Y =

Determine amount of ethat can bemedia and gamut.

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Ink .

3.


Restriction

Register maximum patch for each color.

C = 75M = 80Y = 65

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Ink .

FaFa ep. P he gradient steps.

S

(step 2)

ient patches

.

F n actual 5% gradient change.F n actual 5% gradient change.


Linearization

Ink Linearizationct: The maximum amount of each ink that the media can accept is usually less than 100%. ct: The percentage of each ink that the media can accept is determined by the Ink Restriction st

urpose: The Ink Linearization step redefines the usable amount of ink to 100%, and evens out t

implified 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

4. Measure the 20 theoretical 5% gradient patches.

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

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

act: A 5% gradient change between 15% and 20% might require a 6% ink increase to produce aact: A 5% gradient change between 20% and 25% might require a 4% ink increase to produce a

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Ink .

In

ired) patch values


Linearization

k Linearization

Measured patch values Theoretical (des

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Lin .

(correction values)


earization

Linearization Measured patch values Linearization table

+

Target patch (desired) values

=


Ink Limit (Combined Ink Restriction) .

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 Explanation80 patches per row

1. Print swatch2. Inspect Swatch quickly and look for wet ink. Wet

ink = “over saturation”.

Ref # 0.05 Ref # 4.00


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Controlling ColorICC Profile

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IC .

B* to CMYK.

1.

ta.


C Profile

ICC ProfileNote: A printer ICC Profile is used to accurately translate color data from L*A*

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 Da

3 pages of an ICC profile target.

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IC .

2.

otometer).h.easured Data.

s have been read.


C Profile

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 (SpectroPhNote: The color measuring device reads the actual color value for each patcNote: All of the actual color values read by the Eye One are known as the M

Eye One SpectroPhotometer

Each line of patches is scanned by the Eye One, in sequence, until all patche

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3.


C Profile

Create the ICC ProfileNote: 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


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WorkflowsFor Production

For Proofing

For Photography


Workflow (Photo with a RIP) .

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

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.

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.

Epson InkJet:

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


Workflow (Photo with Epson Driver) .

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

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.

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.

Epson InkJet:

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


Workflow (Proofing with a RIP) .

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 (printing press). A proofing workflow must also be “color accurate” so that company specific colors (logos, etc.) are correct.

Color Model: Source Image: CMYK

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.

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 pressRendering Intent = Absolute Colorimetric (no paper white compensation because there is no paper

associated with this step).

Epson InkJet:



Workflow (Production with a RIP) .

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

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.

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.

Epson InkJet:


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

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