How is it possible that an image colour is not produced as I remember it?The subject of colour has been treated in a vast body of empirical research, scientific theory and heated debate. Colour is a phenonenon that exists only in the brain of the observer: an experience caused by the sensation of photons arriving in the eye of the observer.The camera manufacturer is given the task of capturing these photons (which have the property of wavelength, but not colour) and of causing them to be represented them in a way that creates a recognisably similar experience in the brain of the viewer. The systems engaged in this process are different from the direct physical environment and inevitably lose, modify or distort the original. A colour reproduction is never the same thing as the original. What is important is that the experience created by the reproduction is recognisable the same as the natural object.In digital cameras the colour of the filters placed on the imaging sensor is the starting point for colour creation, these colours are then processed in camera to produce all the other colours required to make the final image. This process involves using highly advanced colour processing algorithms which - in high quality products - are designed to reproduce the image colours in a way that matches the subjective memory of the target audience, who will be viewing the result through a certain colour reproduction system (print, monitor). One of the colours most prone to exposing the differences in the naturally experienced colour and reproduced is the case of purple. The image above shows the visible light spectrum from 400-700nm and also the Infrared and Ultraviolet light spectrums either side of visible light. The colour purple does not exist in the visible light spectrum, it is created both in the eye and digitally from a mixture of red and blue, because of this the reproduction of purple is therefore very subjective and depends entirely on human perception.Some colours are more likely to produce differences because of their spectral characteristics, cobalt blue has a spectrum which goes, in part, into the infrared region which the human eye cannot detect, therefore humans memorise a blue colour which is made up of only the cobalt blue spectrum which the eye can detect. Digital sensors (and film) are more receptive to red content of cobalt blue colour spectrum making the image appear more purple. Although all digital cameras are equipped with a filter to cut infrared light, differences can occur between the colour we see and the colour that is reproduced on the image. Print Share By Email Share By Social Ask A Question FaceBook Twitter