Hi David, squeezee has it dead right. The Pantone (solid to process) swatch book OR the conversion in PS or AI (assuming default settings) - give you the percentages you need to get the colour you want on a web offset press, on a particular paper, with particular inks.
Those numbers will only be accurate in those circumstances. On any other output device/paper you'll need different numbers to get the colour you want.
(take a look at
CMYK? Which CMYK ?! | Hudson to see that illustrated)
Here's the key point though - if your printer/ink/paper combination isn't accurately profiled - there is no way of getting an accurate screen to paper match. You're destined to always produce via the print/assess/tweak/repeat process... and that can be hideous. (especially if you're chasing a colour that isn't possible on your ink/media/machine combination - you can chase those for weeks and never hit them.)
Many designers "don't get" colour profiles. Weird when you think that you guys use them more than anyone else! You're using them all the time, in every element of your work. It crops up in discussion around CMYK most perhaps - just because there's so much bad information out there and printers who also "don't get it" - so you have the blind leading the blind. But you're using profiles in every website, in every browser, in every prog you use, and on every screen you look at. I'm guessing you have a number of browsers, take a look at
Profile check - iPhone in different browsers, especially older ones. Notice how the very same page looks different on each? You can accurately control colour on websites in all browsers provided you understand ICC profiles and how the browsers use them - but if not different browsers could show your website elements as different colours. This explains how safari/explorer8/firefox, and the iPhone4 display things.
iPhone4 and Colour Management | Hudson
Apologies for putting so many links in a post - but I saw the phrase "colour profiles doing strange things" and it rattled my cage. To "get your head around" colour profiles is simple, and will save you hours of time going forward. Here's a link that'll do the job for you!
The Online Colour Management Training Program | Hudson about half way down that page is a link called "sample video". It's actually the whole of the first lesson of the IPA's Colour Management Fundamentals course, and it's free to view. It's 13 minutes long, and it will get your head around colour management. At 12minutes in, it answers the very question you posed at the top of this thread.
I'd be really interested to hear if that sample video gave you information that will be useful in your work, your feedback would be greatly appreciated.
Regards,
Craig
