Calibrated colour imaging analysis of food

Colour is specified by the spectral distributions of three elements light source, sample and observer (CIE, 1986). Each of these was defined by the Commission Internationale de I Eclairage (CIE) in terms of spectral distribution across the visible spectral range, say 400 to 700 nm. The RGB colour signal of a digital camera can be expressed as  

In the human visual system, the JC f and Z tristimulus values are calculated from spectral power as given in the following equations (CIE, 1986). 

It is clear from equations 14.1 and 14.2 that camera RGB values do not match the CIE XYZ values because the camera sensors in general do not have the same 

In order to measure an object in terms of device independent colom from a digital camera, there is a need to correlate the camera RGB signals and CIE XTZ values. This is known as camera characterisation. 

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Hutchings JB, Luo MR, and Ji W (2002) Calibrated colour imaging analysis of food. In MacDougall DB (ed.) Colour in Food, Improving Quality, pp. 352-366. Cambridge Woodhead Publishing. 

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