Clever print management goes far beyond speaking to print companies to steal some great deals on print. We also act as consultants, applying our broad knowledge of print technology and print design to help you secure further savings, meet your company’s financial targets and achieve your other print goals. Here on the PMG blog, we like to share snippets of our print knowledge with the wider world. This week we’re exploring the CMYK colour model: what is it, why do we use it and how does it work?
The basics
Cyan, magenta, yellow and key (black) are the four colours that make up the CMYK colour model. These four colours are applied one-by-one to form the desired printed image. The CMYK colour model is known as a subtractive model, as opposed to the RGB (red-green-blue) model, which is an additive model. CMYK uses white as a base, so when colours are applied, ‘brightness’ is subtracted from the print. In RGB, white is the result of combining the three colours, hence the ‘additive’ label.
Halftoning/screening
At first, it may seem surprising that only four colours are required to print almost any image (strictly speaking, sometimes white ink is also used in some applications). This is where halftoning comes in. This process, also known as screening, involves the use of very small dots of colour rather than solid blocks. The human eye still perceives these dots as a solid colour (unless you look very closely). Different CMYK separations (i.e. each colour) are applied at different angles. When multiple separations are combined in this way, it creates a complex pattern of dots that appear as a solid block of colour when viewed. Colour halftoning therefore allows for hundreds (if not thousands) of different colours from combinations of cyan, magenta, yellow, and black. Halftonig also saves on ink usage.
CMY and the importance of black
Combining cyan, magenta and yellow gives an imperfect black. While the simplicity of using only three colours to print is appealing, black (key) plays a vital role in CMYK printing. It’s used for a number of reasons:
Text is often black, and usually requires fine detail, so the CMY separations must be applied with unerring precision and accuracy in order to create black text that isn’t blurry. It’s simply more practical to include black ink for this purpose.
Cost is another important consideration. Using three different inks to create a black that isn’t perfect is clearly more expensive than simply using a single ink to achieve better results.
Time is also a factor. The combination of three inks takes longer to dry, and may even cause the ink to bleed.
Newcomers to print design should also remember that the RGB colour model tends to be used for digital images, and these files must be converted into CMYK separations before passing them along to the print company.
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