LEARN: CMYK versus RGB - the great conundrum

I have been doing some mentoring recently with some lovely designers and showing them how to create beautiful textile designs in Adobe Photoshop & Illustrator. These are designers who are skilled in their own areas, but are new to the world of CAD (Computer Aided Design) Textile Design. Throughout the training, the age old question of whether you should work in CMYK or RGB mode came up for discussion.

This is a subject that baffled me for a longtime - as a very visual person, who learns by seeing, I struggled with the technical difference. Often I just ignored this setting in the hope that it would either just ‘go away’ or that I would be lucky and guess which one I should be using.

Then one day it dawned on me how I could remember it; I've been sharing this information with my students who also found it useful, so I thought I would share this nugget of information with you too:

OK, firstly, what do they mean:

CMYK stands for Cyan, Magenta, Yellow and Key (Otherwise know as Black).
RGB stands for Red, Green and Blue.


When printing could only be done manually (so not Digital images), printing was done in CMYK - often as a lithographic or screen printed method, or some other method that lays a colour down one at a time.  A bit like mixing paint and layering these on top of each other. The more colour you add, the darker the image gets (finally with the ‘K’ the image is black). So CMYK all together = black (dark colours).

I remember when I was about 7 years old trying to mix the colour black by getting all the poster paint colours available in the classroom and mixing them together in a big tub; the result was a horrid muddy brown colour. I then was told by my teacher (to my great disappointment) that no matter how many different poster paints I mixed together, black was black, a 'colour' in its own right and I couldn’t magically make it. 

Therefore, with regard to CMYK I just remember all the colours I mixed together to get a dark muddy mess. It helps to remind me that the absence of C, M, Y or K, gives you white (or the background colour you are working with) because no colour has been ‘mixed/printed’.



Conversely, RGB, is an 'additive' colour model, where the three colours (red, green and blue) add together to make white, and is more for screen and digital media. It is like a prism, where white is split into the spectrum of colours.  In the case of RBG, it is the lack of these colours that gives you black. Think of a black hole in outerspace if that helps; where the gravitational pull is so strong that even light can’t escape - hence its name 'black hole'. (yes I like sci-fi!)!

With RGB, it is the opposite to CMYK, where all three colours combined give you white. In the same way that if white light is reflected through rain, you get a rainbow.  RBG is often used for digitally printed fabrics etc. and designs that are to be used on a website or in some form of digital content/media.

What happens if you have used the wrong one?

Now, here’s the thing; you can convert from CMYK to RGB quite easily. A CMYK colour to an RGB colour is often identical. This is because RGB as so many more colour possibilities and matching the RGB colour is easier.  However, RGB to CMKY conversion can be less successful; this conversion often results in the colours looking muted, muddy or dull. This is because CMYK can be a more limiting palette.

So which mode should you work in?

Well, it actually pays to do your homework. If you are working for a client or know that you are going to get something printed with a specific manufacturer - check with them first which colour mode they require. In my experience of dealing with many different types of manufacturing and printing industries (ceramics, wallpaper, lampshades, fabric, stationery), they all have different requirements. So it pays to find out first from the company who will be doing the professional printing which colour mode they use. If you are not sure, then I tend to work in CMYK in Illustrator and RGB mode in Photoshop. This is because the type of files Illustrator produces (vector) are more akin to screen printing (a CMYK process). Whereas, Photoshop produces raster files which are more akin to digital printing. Of course, this isn’t always strictly the case, but it can be a good place to start.

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Until next time - April x

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