At school, we first learnt that we could mix all the colours of the rainbow from three primary colours: red, yellow and blue. Then we were taught that light is made up of a continuous spectrum of colours (Richard Of York Gave Battle In Vain) and that all of them together create ‘white’ light.
Our next lesson was that TV monitors and print produced colours in different ways. In both cases, they rely on deceiving the human eye by using lots of dots of a few colours to give the impression of more colours. A TV monitor uses red, green and blue, whereas in print it is mainly cyan, magenta, yellow and black. These are commonly referred to by swots as RGB or CMYK. Even famous painters from the Pointillist movement painted using only distinct dots of individual colour. At University (or as a print apprentice) we refined this knowledge further to learn that the colour we see reflected back from a print will appear differently in different lighting conditions and on different surfaces. We also learnt that one in eight men have some form of colour deficiency. So, how can those of us that don’t live under laboratory lighting conditions ensure that the colour we see on our monitor or from our desktop printer will be closely represented by a printing press costing half a million pounds?
Go right back to some of your earliest masterpieces – painting by numbers. This time though, we will use more than the six colours that were in the painting set. Thanks to some lovely people at Pantone we are able to pay exorbitant sums of money each year to have reference books of colours – a bit like having to pay for Dulux charts (yikes, we haven’t even mentioned BS, RAL or others colour systems yet). These books help to define what a colour is by reference to its colour values expressed in CMYK, Spot Colour, RGB, Lab or # and for different types of surface. It’s all fascinating stuff, honestly. So, if you have set your heart on achieving a specific colour, such as a corporate logo, then please make sure to let us know what you know. Preferably the Pantone reference for CMYK Coated (glossy to most of us). If you are supplying the artwork, or uploading images, then you would be wise to convert Spot colours to your preferred CMYK. Unless you tell us differently, the computers that convert the design file (into the data required by the printer to know which drops of which colour to put where) will convert the file as their clever programming dictates.
There are several colour models but we will concentrate on the four most important ones: RGB, CYMK, LAB and HSB.
This is the colour space you are most exposed to through its use in television and other screens. RGB stands for Red, Green and Blue and is how we see colour on a monitor. Each pixel in your screen can be switched to a shade of red, green or blue with each shade represented by a number ranging from 0 to 255. Black has an RGB value '0 0 0' (R=0, G=0 and B=0). White is represented by the RGB value '255 255 255' (R=255 G=255 and B=255). In total the RGB model can represent more than 16 million shades.
RGB is sometimes referred to as an additive model in the sense that when red, green and blue are combined, they create white.
The printer’s favourite, CMYK stands for Cyan, Yellow, Magenta and Black relating to the four coloured inks used by printers to produce the colour you require – in practice this means as close as they can to your preferred colour given they are using just four inks. Because of this limitation, spot colours specifically formulated to represent a specific colour are used as the only colour or as additional colours. For the same reason, we may refer to using 6 colour processes or more where possible. The original artwork is still set up in the colour space CMYK but the printing press itself is able to better represent the target value by using more than a four colour system by the addition of other colours such as Light Cyan and Light Magenta or Orange and Violet.
CMYK is sometimes referred to as a subtractive model in the sense that when cyan, magenta, yellow and black are combined, they absorb all the light to produce black. LAB
Once again, LAB is a short form for the three values used. Luminance ranges from 0 to 100; the A component ranges from -120 to +120 (from green to red) and the B component ranges from -120 to +120 from blue to yellow. Its main advantage is that it is device agnostic and therefore can be used to accurately translate colours from one medium or device to another.
HSB defines any colour by Hue, Saturation and Brightness.
The main point here is that the colour on your computer screen is unlikely to look the same once printed and that different artworking and printing software may translate the same intrinsic colour differently. It is therefore critical to the final print outcome to start the artworking process in CMYK since this is the colour space that will be used when printing. It is also makes sense for the designer to convert any Pantone or spot colours to CMYK values before sending to print.
For more expert advice, please contact us.
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