CMYK & RGB; The basics.

To put it at the most basic level, when we see a colour photo or picture on a piece of paper we generally see that it is made up from tints of 4 colours; cyan, magenta, yellow & black. When we see colour on a computer screen or any other digital display it is made up from red, green and blue.

Primary colours

Think back to junior school and mixing those poster paints, lots of different colours can be made by mixing basic colours together. Back then, generally we were taught that red, yellow & blue were primary colours. When two primary colours are mixed together we get secondary colours; orange, purple/violet and green. If you then mix a secondary colour with one of the primary colours that made it we get a tertiary colour. Often this is expressed as a colour wheel and within this wheel we gain a range of available colours, this is sometimes called a gamut. I know, for a lot of people this is a bit like being taught how to suck eggs but I want to go through the basics to better explain the more complex concepts.

So with this red, yellow, blue system (RYB) a gamut of other colours are available and this has been used in the art world for the longest period of time. The science of colour has come along a bit since RYB's inception and it was discovered that a far larger range of colours becomes available by using cyan (blue), magenta (red) and yellow (CMY). Then the printing press came along and printers decided to adopt this better system and to add an extra dimension of tone to their gamut; black was added (K for key).

Subtractive colour

I mention the science of colour because it became just that. The older RYB method was more of a discovery rather than a reasoned, understood system. The biggest breakthrough came with the advent of physics with its understanding of how we see colour, that being white light is actually made from all the spectrum of visible colour. Thank you Sir Isaac Newton and your prism.

In other words when we remove a colour from the white light, we end up with the other colours and their mix results in a shade of a colour. When white light reflects off a surface, whatever that surface absorbs or fails to reflect in the colour spectrum hitting it means it only reflects back the remaining colours. Hence why that surface looks the colour it is.

This diagram shows that if a surface appears cyan, it's because red elements of white light has been absorbed and the reflect light you see is made from the blue and green parts of the spectrum.

Additive colour

RGB works in a different way. Its colour gamut is made up by a process opposite to subtractive colour. When a diaode or pixel emits light, it is either red, green or blue and if it emits all three equally you get white light. By adding more light you get lighter shades until you reach pure white, in subtractive colour the more you add, the darker it gets until it comes close to black. This becomes important when considering a design for print, we'll get onto that later on. With RGB the gamut available is far bigger than in printed inks, subtle tones and certain bright colours simply aren't available in CMYK or RYB.

My next post for the tutorials will cover additive and subtractive colour in more detail from the viewpoint of the designer. I'll post a link here once I've written it!