So far as I know, the only reason to use CMYK on screen is for prepress work for something that's going to be professionally printed.
So the only context I can think of where you'd care about accurate screen captures of CMYK images on screen would be if you were writing online help for InDesign, Illustrator, or Photoshop. On Wed, Oct 22, 2014 at 7:34 AM, Craig Ede <[email protected]> wrote: > > > Yes, I think color conversions are that complex. > RGB was designed for monitors allowing a broad range of additive colors in > the form of light (i.e. lit pixels). > CMYK was designed for subtractive printing to paper offering a restricted > range of those colors; many of the RGB colors being "out of gamut" for CMYK, > meaning there is no formula to convert them. > Nobody serious is printing high-quality hardcopy using R, G, and B inks. And > I'm not sure why one would want to use CMYK to print to the screen. > > Craig >> From: [email protected] >> To: [email protected] >> Date: Wed, 22 Oct 2014 03:34:52 -0500 >> Subject: RE: CMYK vs RGB RE: PDF query >> >> Are colour conversions really that "complex"? >> They're just converting colour coordinates in one colour-space to those in >> another, using some straightforward formulae that are hidden under the hood. >> (The choice of formula, and what to do if a colour is 'out of gamut', >> depends on the 'rendering intent', of which we usually have a choice of >> four). >> The conversions will give 'round-tripping' errors if they're out of gamut. >> This is why better Adobe software (Illustrator, Photoshop, InDesign) maps >> RGB and CMYK via a device-independent ("LaB") representation, rather than >> straight from one to the other. >> The problem with FrameMaker is that the conversion algorithms it uses are >> crude rubbish. This is why they frequently give such awful results, not >> because it's "complex". >> >> From previous threads on the Adobe Forums, it seems that the conversion >> formula Frame uses is: >> >> RGB to CMYK: >> C = max(R, G, B) - R >> M = max(R, G, B) - G >> Y = max(R, G, B) - B >> K = 100 - max(R, G, B) >> >> CMYK to RGB: >> R = min(100 - K - C, 0) >> G = min(100 - K - M, 0) >> B = min(100 - K - Y, 0) >> >> ...which gives rubbish results. >> >> David >> >> ____ >> >> From: Jacob Sch?ffer (Grafikhuset) <[email protected]> >> To: <[email protected]>, "'Craig Ede'" <[email protected]> >> Cc: 'framers' <[email protected]> >> Subject: RE: CMYK vs RGB RE: PDF query >> Message-ID: <[email protected]> >> Content-Type: text/plain; charset="utf-8" >> >> It?s definitely NOT easy to explain this. Color conversions are COMPLEX. >> Anyway, RGB -> CMYK conversion is lossy, and CMYK -> RGB is also lossy. >> >> >> >> What is the point of the RGB switch afterall? Why not just pass through >> what?s input and remove this switch? >> >> *** Confidentiality Notice: This e-mail, including any associated or >> attached files, is intended solely for the individual or entity to which it >> is addressed. This e-mail is confidential and may well also be legally >> privileged. If you have received it in error, you are on notice of its >> status. Please notify the sender immediately by reply e-mail and then delete >> this message from your system. Please do not copy it or use it for any >> purposes, or disclose its contents to any other person. This email comes >> from a division of the Invensys Group, owned by Invensys Limited, which is a >> company registered in England and Wales with its registered office at 3rd >> Floor, 40 Grosvenor Place, London, SW1X 7AW (Registered number 166023). For >> a list of European legal entities within the Invensys Group, please select >> the Legal Entities link at invensys.com. 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