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[sebastienne]

Halp!

I clearly don't understand how digital images work.

I've been merrily working on Lashings poster images in the GIMP - all finished and ready to go, but oops, they need to be in CMYK colour format. Only GIMP doesn't support CMYK colour. Oh well.. I think my work computer has PaintShop Pro on it.

So I bring the images to work, open them, and re-save them in CMYK...

And now the purples have gone red, and the emerald greens have faded to mint, and I don't know wtf is going on. Surely computers transfer colours seamlessly from RGB to CMYK every time you hit "print"... so why can't PaintShop Pro do it?!

Can anyone advise?

Luckily, these printers want me to submit my images as PDFs. But I have learnt a valuable lesson for next time...

Comments

[marrog.livejournal.com]

Yeeeeaaaah it's not quite that simple. The thing is that CMYK is a print format, not a screen format, and RGB is, well, vice versa.

Not only will a document not look the same on your screen when it's converted to CMYK from RGB, but it probably won't look the same printed out as it does on your screen, either.

Basically what you need to do if you want to be sure how it's going to come out is tweak the colour levels on your screen until they look back like what you want on the CMYK format, then print it out, preferably on the exact printer you're going to use for the poster run, then return to base, tweak again, ad nauseum or until you're happy. You basically can't know what your poster is going to look like until it's been printed out on the exact printer you're going to be using.

Which, yaknow, isn't an option for most folk, which is why graphic design firms/print shops get to charge what they do for what they do. It's a fucker, sorry.

(Oh, and printings can even look different printed out from the same computer to the same printer if they've been open in a different programme on said computer. WTF, AIR?)

[h0m54r.livejournal.com]

Note also that on Windows at least you can't take a CMYK file and print it. At least not without it being converted back to RGB (using the screen process) first, since the Windows print subsystem knows only RGB. Then it's converted to whatever colour space the printer is working in by the printer driver. (I think this is why you get two different outputs for the same CMYK file in different programs - they both have to convert down to RGB and will do so differently.)

Asking clients to provide images in CMYK format means that printers don't have to worry about matching colours from one person's screen to their printer - the RGB colour space contains colours that can't be printed (at least not on all printers). It shifts the colour management problem to the customer. Unfortunately in many cases (i.e. when work is being done by people other than publishing/design professionals) this isn't where the problem should be left, as it will lead to substandard output (for the reasons discussed). It will also lead to poor customer experience and a negative perception of the industry or at least firm. Basically every dealing I've had with the print industry has given me the impression that they really don't like having customers (or at least not short-term single-run customers) and would rather they went away.

[andustar.livejournal.com]

The files I sent you were already in CMYK. I should probably have warned you to keep them that way :S

It's not possible to transfer colours 'seamlessly' from CMYK to RGB. They're different colour models. CMYK works by printing dark ink onto white paper, and RGB by mixing light. There's not a one to one correlation of colours between the two. It's a bit like assuming a piece of writing translated into a different language should be fully translateable back to the original without any errors. This is why working with print files on a monitor is a bit of a pain.

I'm sorry, I did vaguely mention it in my email but I shouldn't have assumed you knew what I was on about!

Хороший блог!

[derronavu.livejournal.com]

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