Printing

  1. What is 4Colour Process (CMYK)
  2. What are the other ink colours?
  3. Paper & Envelope Sizes

What is 4Colour Process (CMYK)

Printing In order to be printed, colour photographs need to be separated into primary colours. The primary ink colours are called "Four Colour Process", the colours being cyan (bluish), magenta (pink/reddish), yellow and black. Similar inks are used in colour inkjet printers.

Printing presses can only print solid colour in the image area, while no ink prints in the non-image areas. To achieve the required result the photograph is converted into a pattern of very small and clearly defined dots of varying size. This process is called screening. The printed result is an optical illusion relying on the eye to mix the dots of the four process colours. The pictures displayed right show the result (top) with the four colour process separations underneath. Amounts of the four process colours differ across the image combining to give the final mix of colours.

CMYK is a subtractive colour model used in colour printing. This colour model is based on mixing pigments of the following colours in order to make other colours:

  • C=Cyan
  • M=Magenta
  • Y=Yellow
  • K=Key (black)

Four-colour process cannot adequately simulate all special colours. At times results can be quite similar, but in many cases, it is not accurate enough and additional special colour inks are used to achieve the required result.

Short for Cyan-Magenta-Yellow-Black, and pronounced as separate letters. CMYK is a colour model in which all colours are described as a mixture of these four process colours. CMYK is the standard colour model used in offset printing for full-colour documents. Because such printing uses inks of these four basic colours, it is often called four-colour printing.

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What are the other ink colours?

Special colours are those where four-colour process is not used. Examples are metallic, fluorescent and Pantone (PMS) inks.
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Paper & Envelope Sizes

The following tables show the range of sizes (in millimetres) that can be obtained by the progressive subdivision of the basic sizes A0 and B0. These are finished trimmed sizes
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