While working with transparent colors, I noticed the peculiar issue that when flattening transparency, the color changes quite noticeably.

I'm in CMYK colorspace, and I have below two shapes with the same basic CMYK red color, but the left shape is at 35% opacity.

enter image description here

After flattening transparency or rasterizing with white background, this is the result: enter image description here Interestingly, when I place a white shape behind the transparent one, it starts to look more like the flattened image.

enter image description here

This leads to the strange conclusion that the white artboard isn't really white? Why do transparent colors render differently on an artboard and on a white background?

UPDATE: This might be a bit irrelevant, but to add to the mystery, after turning on Simulate Colored Paper in Document Setup, and inserting the screenshots used here into the document, they seem to become transparent outside the artboard! And turning on Overprint Preview does not help.

enter image description here

  • 2
  • Just checked it. Really nice work on testing and trying to figure it all out! Up-voted your answer over there. Turning on simulate colored paper seems to be the best option, but it's weird they don't have it as default. What possible use would there be for turning it off?
    – fadelm0
    Oct 23, 2016 at 7:27
  • I suspect there's no use, just an oversight on Adobe's part!
    – Cai
    Oct 23, 2016 at 7:30

1 Answer 1


Check this post because this question was recently discussed here And yes the artboards in Illustrator are not interpreted as white as many of us believed for some time now and some of us still believe. So transparency will work differently over the artboard that is understood as "nothing" by the software or over a white object.

Hope the link below helps with all the answers and comments.

Opacity problem over white object in Illustrator CC

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