BobKipper

That's really helpful BofG. Thanks again. I had another look through the help but couldn't find it mentioned.

Many thanks BofG - that would make sense. Not sure why this didn't occur to me. Is that the case even if the document colour format is the same but the profiles are different? Any idea if this is documented in the help? I'll have another search.

If the colour model I select via the colour panel doesn't match the model of the document, can anyone tell me how the values are converted? For example, if I set the document to 8bit RGB and choose the sRGB profile, then I select the CMYK sliders on the colour panel for input, how are the values converted from CMYK to RGB? There appears to be no obvious way to select an 'input' profile (unless I've missed it). The help does hint at the conversion being approximate, but doesn't say how it's done. Is a generic mac profile adopted, perhaps? Using Apple's colour picker, it's explicit what profile space you're inputting with. Hope someone can help.