Considering paper gamut when printing vibrant photos
Tian Yang | July 19, 2015
After a friend’s recommendation, I bought a roll of Moab Colorado Fiber Satine 245 and made a custom icc profile for it (you can download the profile here). This paper yields a gamut that is 17% smaller than my current reference paper Hahnemühle Photo Silk Baryta.
To examine what kind of difference this 17% of gamut volume will make, I chose one of my photos as the test target, which has very vivid magenta colors.
After extracting all the unique colors from the focused area, I placed them into 3D space along with the two gamut shapes at concern. The orange wireframe represents the boundary of Photo Silk Baryta’s gamut, whereas the cyan wireframe represents the boundary of Colorado Fiber Satine’s gamut. As you can see in Pic. 2, there are lots of magenta colors that are too bright or too vibrant for either of the paper-ink combinations to print.
In order to print colors that are outside of any given paper gamut, printer drivers or RIP software will render the colors into the available gamut according to your chosen Rendering Intent. For this particular photo, I chose Relative Colorimetric which has yielded better print result than Perceptual.
Let’s see some visualization about how the calculation is done. In Pic. 3 and 4, each thin magenta line tells us how far and which direction one out-of-gamut color has to travel in order to fall into the available paper gamut. The outside ending of the line represents the original color, and the ending inside of the gamut area represents the rendered color that is to be printed on paper. The difference between the original color and the rendered one is calculated in Delta E and in turn represented proportionally by the length of each line.
For even greater contrast, I combined Pic.3 and Pic. 4 together to generate Pic. 5. I turned all the vector lines in Pic. 4 into cyan, and all the rest lines in various colors are the lines from Pic. 3. Green means shorter than 1 Delta E in length. Yellow means from 1 Delta E to 3 Delta E. Orange means from 3 to 6 Delta E. And finally Red means longer than 6 Delta E. As you can see clearly, for any beyond-gamut color to be printed on paper, the rendering process has to be of bigger measure if you are using Colorado Fiber Satine.
When printing vibrant photos with out-of-gamut colors, you inevitably lose luminance, shift hue and desaturate the color. For this particular photo, because the color is about an artificial lighting situation, I’m not so concerned about the accuracy of hue or saturation, but I do want to keep as mush brightness of the magenta light as possible. Therefore I chose Photo Silk Baryta as the paper because it allows less luminance drop.
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