What is CMYK?

Why does my file have to be CMYK?

Why does my file have to be CMYK?

By In information On September 21, 2015

Why does my print ready file have to be CMYK?

The printing process requires files to be supplied as CMYK. This format is used by all offset/litho printers and whilst digital presses can work with RGB files, the on-board rip (computer) doesn’t always do a very good job of converting the colours and you could end up with something you didn’t set out to achieve in the first place. So it is always recommended to make sure your colours are converted before sending to print, so you get exactly what you set out to achieve.


Whilst we all think we can put artwork together, some applications cannot work in CMYK. For example Word, Power Point, CorelDRAW (unless you are a pro and know how to create the CMYK file) and many other basic/cheaper desktop applications cannot work in CMYK. The key is to know how to provide a CMYK file from that application, or give your file to an experienced designer/print operator who can adapt your file to print correctly.

The software packages I have just listed above work in RGB – Red, Green, Blue. This process is not what is used to print on a press, the press has ink in to print cyan, magenta, yellow and black, and this combination produces all the colour variances. RGB is how your monitor displays colour, and how files display on the web/tablet/phone.

You can also print in spot pantone colours on a press, including metallic (gold, silver, bronze etc) and fluro (vibrant bright pink, yellow, greens etc). However, this process is more expensive, because you are dealing with special colours, not the standard CMYK. These inks cost more and each time you want to use a spot colour, the press has to be cleaned down to put that particular colour in the unit that prints on the plate. There is a lot more choice when using spot colours; you can achieve a much wider colour gamut that cannot be achieved with just CMYK alone. Whilst some RGB colours are vibrant on the screen they do not print this vibrant on the press in CMYK, so that is when you need to look at a spot colour choice instead. Whenever I create a concept proof I am working in CMYK, whilst your monitor or desktop printer may not be calibrated to the colours achieved on press, I will not create a concept using RGB, as this is not what you will get when it goes to print. If you need to see a colour proof before a big print run, I will be more than happy to provide one for you to sign off on.

Hopefully I haven’t gone into too much detail and confused you, but enough for it to make sense.