Dye Sublimation Color Management

Achieving Accurate Color Output Using Standardized Processes

Color Gamut

The gray area represents the entire chromatic range. The colored triangle represents the color display. This is a typical CRT gamut reflected by the sRGB ICC profile.

Definition of GAMUT 1.

The subset of colors which can be accurately represented within a given color space or by an certain output device and ink combination.

2.

The complete set of colors found within an image at a given time. Converting a digitized image to a different color space, or printing it to a given medium generally alters its gamut.

RGB and CMYK

RGB and CMYK are two different color spaces. The RGB color space uses light in colors of red, green, and blue to create the visible spectrum. Our eyes see color in terms of reflected light, so the observed world is closer to RGB than CMYK. That is why native RGB devices that use light to create color, such as film recorders, scanners, and cameras can reproduce color fairly accurately.

RGB. Three colors of light, red, green and blue make white light. Cyan, magenta and yellow are also combinations of RGB.

The intensity of light also changes the color.

CMYK. Three inks, cyan, magenta and yellow make black. In practice this black lacks intensity, so a separate black (K) is usually added. Red, green and blue are made from CMYK.

Typical Color Spaces

Comparison of typical wide RGB gamut for a color accurate display, standard RGB gamut for an ordinary color display and a typical CMYK gamut for standard pigment inks.

The Adobe RGB profile reflects the wide RGB gamut, the sRGB profile reflects a standard RGB gamut.

Rendering Intent

Handling Out-of-Gamut Colors • • • • • Standard Rendering Intents Perceptual Relative Colorimetric Relative Colorimetric Black Point Compensation Absolute Colorimetric Saturation

Rendering Intent

Perceptual Graphic to be printed Printer • • • • Relationships among colors are preserved Color space is uniformly shifted Absolute colors are not preserved Technically reversible depending on RIP

Rendering Intent

Absolute Colorimetric Graphic to be printed Printer • • • In gamut colors are preserved Out of gamut colors are shifted Not reversible

Rendering Intent

Relative Colorimetric Optional Black Point Compensation • • • • • • Absolute Colorimetric with Compensation for White Black Point Compensation also compensates for Black In gamut colors are corrected for white and black points Out of gamut colors are shifted Black Point Compensation not supported on Adobe Output Not reversible

Rendering Intent

Saturation • • • Only CIELAB Lightness or L* is preserved All colors are shifted Not reversible

Simple Color Management

Chromatic and Ink Limitation Clipping Causes Unpredictable Results

ICC Color Management

Standards Based Approach to Achieving Predictable Color

Standard Adobe Design Environment

The standard Adobe design environment is RGB using the Adobe RGB color profile. The target CMYK space is typically US Web Coated (SWOP) : an offset press.

Color Conversion Space

ICC Profiles Connect Design and Output Spaces Using the L*a*b* Space as the Intermediary RGB L*a*b* CMYK

Color Conversion Space

R G B

34 74 141 28 63 123 4 48 97

L a

15 9 12 3

b

17 16 -56 -46 -33

C M Y

98 80 8

K

39 97 79 14 58 95 71 26 81 ICC Profiles are the basis for transforming color from the source space to the color conversion space and then to the printer. They can be thought of as tables that define conversions to and from L*a*b* space. Color values not in the table are interpolated.

Late Binding

RGB devices will have distinctly different white and black points than CMYK output in relation to the colors that are produced. RGB Display Device CMYK on White Fabric Conversion between RGB and CMYK accounts for differences in gamut and white points. Optionally there can be compensation for differences in the black point. Late binding allows these to be mapped accurately to the final output device.

Output CMYK Color Mapping

Navy Blue Pantone 282 Adobe RGB: 0 45 98 Dye Sublimation CMYK (Elvajet) Differs with Rendering Intent Proprietary RIP algorithms also impact the color output. SWOP CMYK: 100 68 0 54 Absolute: Perceptual: Relative BPC: Relative: Saturation: 96 82 14 71 96 73 11 61 94 65 10 71 95 80 17 75 97 78 09 61

ICC Color Management

Standards Based Approach to Achieving Predictable Color Pantone Spots Late binding: Design in RGB let RIP convert to CMYK Modified late binding: Design in RGB and Named Colors

ICC Color Management

Standards Based Approach to Achieving Predictable Color Single Environment Two Profiles 1. Printer Profile RGB to CMYK 2. Named Color Profile • • • RIP optionally bypasses printer profile and uses the named color formula if it exists.

Unnamed colors should be specified in RGB.

Do not use raw CMYK specifications.

ICC Color Management

Linearization: Controls Perceived Optical Density 45% color value 1.25 optical density 1.25 optical density ?? pixel value

ICC Color Management

Ink Limits: Improve Optical Density and Control Chromatic Shifts Gray Cyan Magenta Black Blue Red