false colour

Definition: Assignment of arbitrary colours to an image. * Usually applied to images derived from extended spectral range imaging e.g. (a) colour film with infra-red sensitivity (b) multi-spectral imaging from remote sensing satellites e.g. reds may be allocated to infra-red, greens to visible wavelengths, blues to ultra-violets.
Playing with colours
Infra-red colour film is, ipso facto, false colour because we cannot see infra-red so what colour can it be? The answer is 'red', which means that actually red objects must be shown as another colour -- usually green -- while green objects are shown blue. Film consists of the usual subtractive tri-pack structure but: cyan dye is infra-red-sensitive; yellow dye is green-sensitive and magenta dye is red-sensitive. Poor old greens obviously get squeezed out to grey i.e. they are not 'seen' at all by such films.

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