What is CMYK?

What is “CMYK” or “Four colour process”? – using tints

In four colour (CMYK) printing, before the file reaches the printing press all the colours are converted into three primary ink colours (red, yellow and blue) together with black. Using mixes of these colours, a large number (or gamut) of colours can be reproduced. The principle is similar to mixing paints at primary school – red and blue make purple, yellow and blue make green, and so on – but of course far more technical. CYMK produces a good range of colours and, of course, full colour photographs.

The four colours used in four colour process printing are Cyan (blue), Magenta (red – or more of a bright pink), Yellow and Black. Abbreviated to CMYK (with K standing for black). The process is the same whether printing lithographically or digitally.

Tints

Tints are a vital part of printing. Shades of any colour can be produced by clustering together groups of extremely small dots with white space between. The greater the white space (or put it another way: the fewer fine dots in a specified area), the lighter the colour will appear.

Tints are described as a percentage – a 50% tint will produce a colour half the strength of the original. The ink itself remains the same colour, but by having half as many fine dots in an area instead of a solid block, to the eye the colour is lighter.

Four colour process uses mixes of tints of each of the four colours to great effect. Interestingly, rather than the inks physically mixing together (like the paint in our primary school analogy), using a clever clustering of each of the Cyan, Magenta, Yellow and Black dots (at a microscopic level) tricks the eye into doing mixing and seeing a different colour.

For example, a group of 50% yellow dots with 50% blue dots will appear as a green. Gradual changes in the percentages of all the four colours produces a surprising large range of different colours and will faithfully reproduce full colour photographs. The spaces between the dots are as vital in CMYK colour reproduction as the coloured dots themselves.

Nowadays, the creation of these dots in tints is entirely the task of a computer. All pre-press reproduction is processed by computer and output direct to the digital press or litho printing plate. A colour document can be converted to “CMYK” at the touch of a button. When we started, that process was performed in a dark room all manner of specialist camera equipment.

This is a very brief overview into the use of tints but please, if you have questions do let us have them as we would be very happy to talk further on the subject!

Remember that with our lithographic printing, a huge range of coloured inks are available beyond the four process colours, including fluorescents and metallics. Spot colours can be added in addition to the CMYK process for extra effect!