Ebook The Concept of Colour Renderin Revisited
Since the introduction of the currently used colour rendering index (CRI) calculation 1 method, many new light sources have been introduced and new methods for colour appearance evaluation have been developed. As early as when the so called tri-band fluorescent lamps became available, based on an optimisation of luminous efficacy and the colour rendering, questions have been raised on the validity of the CIE method of calculating colour rendering. In the mean time a number of new light sources, with different spectral power distributions became available, most recently those based on light emitting diodes (LEDs). It is anticipated that LEDs will be used in general practice interior lighting as well (several trials have already been carried out). Visual experiments show that the colour rendering impression and the calculated colour rendering indices do not correlate well for these sources 6.
At the time, when the CRI calculation method was elaborated the most commonly used colorants have been pigments with broad absorption bands. At present many narrow band colorants are also in use, as e.g. coloured offset printing inks, inks used in desktop printers, etc. It is important for the imaging industry to know whether the every day illumination used for viewing the results of their work will render the pictures in the same way, as seen under their proof-lights, i.e. whether colour constancy holds for their products or not.
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