Let’s take a look at the four photos shown below. Each of the photos is shown on four different screen monitors. Note how different the colours look on the monitors. Before colour management is implemented on the four devices, there are visible colour differences due to varying hardware technologies and colour settings. The default colour settings, for example, colour temperature, saturation and contrast, you find on your home’s display will generally cater to the colour needs of typical use. However, for commercial printing companies and for freelancers and professionals whose work requires colour precision, colour management becomes essential in their workflow.
LCD monitors of the same model will also exhibit colour mismatch due to deviations in backlight modules and colour filters. Calibration can reduce the colour differences between displays.
Below are devices that use different colour systems to produce colour. Optical devices use additive colour mixing while print devices use subtractive colour mixing.
1. Optical input devices: cameras, scanners
2. Optical output devices: monitor displays, projectors
3. Print device: printers
Additive colour theory states that colours are produced by mixing light, specifically red, green and blue light. These three colours are called the primary colours for additive colour model. Other colours can be produced by mixing various amounts of red, green and blue light to create secondary colours: cyan, magenta and yellow. Mixing red and green light gives you yellow light. The overlap of green and blue produces cyan. By combining blue light and red light, magenta is produced. When all three primary colours are added together, white light is created.
The commonly used RGB colour space uses the additive colour model, where red, green and blue light are mixed in various amounts to create a broad range of colours.
In the subtractive colour system, colours are produced by mixing colorants. Certain colours of light are absorbed (subtracted) by the colorants whereas others are reflected and seen by the viewer. The subtractive primary colours are cyan (C), magenta (M) and yellow (Y). If we mixed yellow and cyan, we would get green; mixing yellow and magenta gives us red; and combining magenta and cyan produces blue. Theoretically, the combination of all three primary colours would give us black; however, in reality, a dark brown results. Hence, a fourth colour, black (K), is added to colour printing to compensate for the imperfect colour produced from the primary colour trio.
This subtractive colour model is referred as the CMYK colour space, comprising of cyan (C), magenta (M), yellow (Y) and black (K).
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