Color modes RGB CMYK

[ihnacy]

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Hi. I'm creating a logo in AI CS5. The document is in CMYK mode and for a certain element I use a pure Cyan color (C100 M0 Y0 K0). The professional CI-books of giant corporations have a color specification in CMYK, RGB, sometimes Pantone CMS. But as I checked in some of the CI-books, the RGB values are not just converted values that are recalculated from CMYK in Color Window in Illustrator or Photoshop (in my example that would be R0 G158 B224). They are somehow different. My question is: how to proceed when I have ready-made CMYK values? How can I get RGB values that will best match the values from CMYK mode?

Would be grateful for any suggestions for a beginner!

[James Jones]

Not sure what you're asking really?

[ihnacy]

Not sure what you're asking really?

Well, what is the procedure to find the RGB colour for my cyan (C100 M0 Y0 K0) that will best fit its equivalent in CMYK mode using a graphic tool like Illustrator or Photoshop? My project is in CMYK mode and it contains some CMYK colours that need to have their equivalents in RGB. Straight reading the RGB coordinates from the Color Picker window when CMYK is (C100 M0 Y0 K0) doesn't seem to be the right move.
In other words:
I designed a logo in Adobe Illustrator. Let's assume that it is a cyan rectangle (C100 M0 Y0 K0) and the document is in CMYK mode. I'm writing a CI book in which I'd like to attach colour specifications, like here:
ht tp://identity.uclahealth.org/body.cfm?id=84
So what do I do next to have both CMYK and RGB coordinates? Because RGB 83 104 149 is not recalculated CMYK 75 35 0 7.

[Cwilk]

There is no exact reference for an RGB to CMYK conversion because the CMYK colorspace is much smaller than an RGB ... so they will always look different.

A good example is when you see that something is 'Out of Gamut'. That means that there aren't enough colors in the CMYK spectrum to convert properly to RGB.

So my answer is that it doesn't matter because there is no direct conversion that will work exactly.

[ihnacy]

Thanks. So perhaps you could explain me this: when I have a document in Illustrator that is in CMYK color mode and I choose Cyan (that is C100 M0 Y0 K0) I get RGB as follows: R0 G158 B224. But on the other hand when I create a new document and set it to RGB color mode and pick RGB color 0 158 224 (same as before) I get "Out of Gamut" warning. Why? Shouldn't the colour be recalculated to CMYK as 100 0 0 0?

[Cwilk]

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Thanks. So perhaps you could explain me this: when I have a document in Illustrator that is in CMYK color mode and I choose Cyan (that is C100 M0 Y0 K0) I get RGB as follows: R0 G158 B224. But on the other hand when I create a new document and set it to RGB color mode and pick RGB color 0 158 224 (same as before) I get "Out of Gamut" warning. Why? Shouldn't the colour be recalculated to CMYK as 100 0 0 0?

It could be that it's too difficult to program to calculate all RGB breakdowns into a CMYK when converted because they don't really convert? I wouldn't want that programming job.