Specifications

The Digital Fine Print Course

Refining a Fine Print

Editing Out of Gamut Colours

Whenever the Perceptual gamut mapping intent in a destination profile fails to adequate-

ly separate out-of-gamut colours, then these colours will need to be manually edited into

the destination gamut. One approach compresses the colour gamut (range of saturation)

to bring the image into gamut and then expands the tonal contrast (range of tones) to

compensate for the reduced colourfulness. The LAB format is an ideal working space to

gamut compress an image because it separates lightness (tone) from colour.

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Lab edited image softproofed in U.S. Web Coated (SWOP) v2

The image is converted into LAB and softproofed through the output profile, in this case

U.S. Web Coated (SWOP) v2 which is a standard press profile for magazine reproduction.

The out-of-gamut greens are located in the a* channel (green to magenta) and not the b*

(blue to yellow) channel. Reducing the gradient of the a* curve therefore reduces the

range (gamut) of greens in the image. To compensate for the reduced green ‘vibrancy’,

the gradient of the L* (tone) curve is increased to enhance local tonal separation.

Lightness (Contrast) Curve a* (Magenta to Green) Curve b* (Yellow to Blue) Curve

The Layer Mask removes the gamut

compress from the orange (magen-

ta-yellow) barriers behind the car