Colours sampling and illustrator- never get the right colour

Question

Using mac colour sample tool, I sample a colour from a website ,get its RGB, then try to set it to an object inside Illustrator,

-in illustrator I am not on grayscale (cmyk)

-I set the colour sampler tool of the mac to be "RGB Adobe" , or "RGB"

-I get some colour sample from a website, then goes back to Illustrator

What happens, is that when I set the RGB on illustrator to an object, I get a similar colour (when sample it again with the tool I get different result).

Sometimes Illustrator even change automatically the colour I'v set ! It seems to me there is some problem in general with intensive colours.

(CS6, MAC retina display)

Thanks.

Answer 1

Your document is CMYK, the color you are sampling is RGB. When you set that color in your Illustrator document it is being converted from one color space (and mode) to another. Color conversion from one color mode to another will never be perfect and RGB contains a lot of colors that simply cannot be represented in a CMYK color space.

It depends on the exact color profiles being used and the conversion method but your colors most likely won't be the same.

A visual of the different ranges of colors possible in different color spaces:

If your output is for any digital medium (and will therefor be RGB) you need to set your Illustrator document to work in RGB. If your output is intended for print then you're stuck with converting your colors to CMYK and not getting exact RGB colors.