In ISO standards it can be found information about tone value reproduction
limits depending on screen ruling (12647-2) or print substrate type
(12647-6.2).
For example:
-in ISO 12647-2 for screen ruling between 40 and 70: 3 % to 97 %,
-in ISO 12647-6.2 for coated paper 3 % to 85 %.
I would like to not discuss about this specific values rather about how to
achieve CMYK files with some tone value reproduction limits.
We can get CMYK files in different ways. But my wondering is concerned in
getting CMYK files from RGB files. One way to do this is using CMS:
RGB file through source profile to LAB to (through) destination profile to
CMYK file.
But how to create an ICC CMYK profile that creates separations with some
tone value reproduction limits?
During creating an ICC profile in separations options we can find some
options for example: TIL, black (!) start, UCR, GCR, etc. Why it is
impossible to adjust starts for rest of colors (CMY)?
For example using “isocoated.icc” and sRGB and RGB image after conversion
(perceptual) the highlights are C 0% M 0% Y 0% K 0% or C 1% M 0% Y 1% K 0%.
Another way to get separations with specific tone value limits is to cut in
RIP highlights and let them start from 3%, but this operation doesn’t
compress the image range but cuts the image highlights resulting in image
loss.
Summarize:
How to get correct CMYK files with specific tone value range using CMS?
Question on different subject:
Does anyone know any free software that lets plot given LAB values on LAB
diagram (3D diagram) or AB values (2D diagram)?
Simon
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