CMYK? Which CMYK ?!

When you don't specify your colour space by embedding an ICC profile, you aren't specifying your colours. "Just print it CMYK" doesn't mean anything. Or rather, it means lots of things.

If I print 100% cyan from an HP Designjet, and 100% cyan from a Mimaki JV3, I get the same colour right? If I get 100% red from my monitor, and 100% red from your monitor we see the same colour right?

Well - NO! We don't. They're unlikely to be very different. 100% cyan from two commercial printers won't be a dark blue and a sky blue apart. But the chance of them being such a good match you can't see a difference is tiny.

So 100% Cyan does not ensure we get the same colour from each machine, it just ensures we get 100% of that machines cyan ink. 

So "just print the CMYK numbers" only ensures that you get that image, on that machine. That machines version of your colour numbers. Those numbers in that machines colour gamut. (to be accurate, those numbers in that machine/settings/media combination.) in colour management terms you are assigning the profile of that device setup to your image. By definition, you are changing your colours, because you won't have created that artwork in that colour space.

Question 1: Does it matter to you?

These colours are all the same as far as CMYK numbers are concerned. 30C, 50M, 0Y, 0K. If this variation is something you can live with, if close is close enough, then you really don't need to invest any time in tightening up your colour communication. 

If however, you want the colour you specify to mean the same colour to each and every printer/monitor you send it to, then you need to define WHICH CMYK space you are working in. (or WHICH RGB space, if you're working in RGB.)

Question 2: How do I explain the colours I want accurately?

The bottom right patch is 30/50/0/0 in US Web Coated SWOP v2, the AdobeCS default CMYK space. We'd assume this space if you sent a CMYK doc without telling us the space.

However. if you say "I want 30/50/0/0 in the US Web Coated SWOP v2 colour space" we, and any other printer worth knowing, know exactly what colour you require. You do this by including the ICC Profile where possible, OR  by simply telling the printer the space the numbers are in. 

It matters far less WHICH space you are in, than not specifying a space at all. 

If, like many of our clients when we initially discuss colour, your response is "I've always just sent CMYK numbers and prints have always been ok." there are three things to consider.

1) Have they really been ok? if you've been working in US Web Coated SWOP, and your printer has assumed it, then your prints have been ok, although you may still have had issues with elements of the prints, or problems with comparisons with other sources.

2) How much has being vague about colour really cost you? Either you've got lucky, or someone is testing your artwork to check that it looks "ok". Perhaps running a print or two to check spot colours. They're not doing that for free, the cost is built in to the purchase price. The less pre-press time your files take, the harder you can bargain on price.   

3) How dull have your prints been? There's a full article HERE about wide format printing and the SWOP workflow. Suffice it to say, the default CS space, US Web Coated SWOP, is a small space. Your wide format printer can print more colours than you can specify in SWOP. There are more vibrant colours, deeper shadows, brighter whites, than you can ask for if your artwork is in SWOP. Your digital camera can capture colours you can't specify in SWOP.

In the meantime we'll keep asking "which CMYK", helping Hudsons' customers make their graphics stand out from the crowd by using all those lovely colours that SWOP user's can't even specify.