Inside digital cameras : RGB and CYMG colour filters
November 13, 2007
There are two types of colour filters used in digital photography. They are RGB and CYMG referring to number of coloured filters used in each method. In RGB type colour filter, filters of three primary colours are used – Red, Green and Blue with half of the colour elements are green as the human eye is more sensitive to this colour. In CYMG type colour filter, cyan, magenta, yellow and black filters are used and type of filter is used mostly in colour printers and a few digital cameras.
RGB Filter
RGB uses primary or additive colours (red, green and blue) and mix them in different amounts to produce various colours. When these colours are added in exactly equal amount, the result is you will see white colour. When there is no light hitting on the photosites, you get black. In this method, red and green filters sit over the pixels (photosites) on the sensor arranged one after another. The next row of pixels is covered by similarly arranged array of green and blue filters and so on. This is how the filters are arranged in a Bayer filter or in display devices like televisions and computer monitors. Recently, improved RGB patters are used in digital cameras to produce better results.
CYMG Filter
CNMG colour filter uses four colours - cyan, magenta, yellow and black to capture the colour information of the image. In this method, colours are produced using reflective and subtractive technique and this type of filters use slightly light colour tones when compared with RGB. Since, they use lighter colour tones, they allow much more light to fall on pixels of the sensor and work well with sensors that are prone to noise during capturing of the image.
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