Printers use the CMYK Colour Model, a Subtractive Colour Model for printing, beause addition of ink is subtractive. It includes cyan, magenta, yellow and black (key) colours. Black is used to adjust the shadow and contrast of images.

Inks used in colour printing are semi-transparent and can be printed on top of each other to produce different colours. To vary the amount of ink, a method known as screening is used, where lighter shades are represented as tinier dots. This is like mixing white paint with colours to lighten them, but in this case white is the paper itself. In colour printing, the screened image, or halftone for each ink colour is printed in succession. The screen grids are set at different angles for each ink, so the dots form tiny rosettes, which when viewed from a disatance appears to form a continuous-tone image.

The halftones can be viewing a printed picture under magnification.

Types of Printers

Inkjet
Supertank (InkTank)
Laser

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