Conversion from CMYK to Grayscale is wrong
Converting CMYK values to Grayscale will not give the expected result. C=50 M=50 Y=50 K=50 converts to 100% Grayscale in a CMYK document.
The same C=50 M=50 Y=50 K=50 converted to R: 92 G: 81 B: 76
in an RGB document it converts to 67,16% Grayscale, which looks more like the expected Gray value.
Ton
shared this idea
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Rob, based on the swatches in Swatches, this document, while being an RGB one, was created in CMYK color mode initially.
This means Black is CMYK 0-0-0-100. And K100 is lighter than RGB 0-0-0 (with my current Coated FOGRA39 profile it gives 29-29-27 when converted to RGB).
Color intent is extremely important. It defines defaults and dictates conversion rules for grayscale. If you convert each stop from being a gray tint into RGB — it will start matching. Same happens if you changed the color mode of your document back to CMYK.
However, the problem with lighter gray conversion indeed exists, and this case is only one consequence of it... I will merge this with a larger report. -
Rob Woods
commented
This is a massive issue! I am trying to make a gradient between a 25% grey and a 100% black. Solid colors of both are under the shape with the gradient applied and it is quite obvious that the gradient doesn't match the solid colors. This needs a fix ASAP! I pay a monthly subscription for working software, I don't want to just wait until someone gets round to fixing these bugs.
I run MacOS 10.14.5 and Illustrator 23.0.4
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Egor, I cannot remember when this started, but there are more problems with grayscale in Illustrator, although one mentioned in this report seems to be solved: https://illustrator.uservoice.com/forums/601447-illustrator-desktop-bugs/suggestions/41260390-embedded-grayscale-image-in-rgb-document-becomes-t
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Yes!
And this is also why probably shades in Color Guide look very much different for CMYK and RGB (but that’s my guess).
I have no idea when it started and should run some tests to figure this out.
Ton, do you have any memories on this? -
And when pasted from an RGB document into a CMYK Document, the same Grayscale percentages display lighter. See second attachment.
