The CIE Colour Rendering Index (CRI) is arnwell-known descriptor for the colourrnrendering properties of light sources. Beingrna single number the CRI is a veryrncomprehensible figure of merit. Thernaccuracy of the CRI in predicting specificrncolour rendering aspects is relatively low.rnCRI is an average of only 8 colours andrnaccounts only for the size of the colour shift.rnFurthermore the CRI is specifically related tornthe aspect of colour fidelity. Other colourrnaspects such as colour preference, colourrnharmony, colour appearance are notrndescribed by the CRI. Ever since itsrnintroduction the CRI has been criticized butrnthe metric still stands and is commonlyrnused.rnIn the past decade solid state lighting hasrnstrongly developed. In the development ofrnsolid state light sources visual experimentsrnhave been done which showed that the CRIrnnot always matched with the results of thernobservations. This has led to a newrntechnical committee within CIE with thernobjective to improve the current CRI or torndefine a (possible additional) new metric.rnPossible improvements to the CRI can bernthe choices for other sets of object colours,rnother colour transformations and the usagernof other (better) colour spaces. However ifrnthe index remains a single number the mostrnimportant question is still whether this will bernseen as a significant improvement by bothrnmanufacturers of light sources and users.rnManufacturers want to communicate thernrelevant properties of their products in arncomprehensible and meaningful way. Forrncolour rendering this implies that only onernaspect can be considered being colourrnfidelity. Other colour aspects such as colourrnappearance, colour harmonies etc. dependrnon the application and cannot be used as arnlamp metric. So until now manufacturersrnhave used the CRI as a single numberrnrepresentation for colour fidelity. To endusersrnsuch an average number provides norninformation on specific hues nor on therndirection of the colour shifts. So thernchallenge is to find a way to providernadditional information on colour rendering tornend users in a comprehensible way. In thisrnpaper we will discuss a number of ways tornimprove the information on colour renderingrnproperties of light sources to end-users withrna focus on making the information more huernspecific and nevertheless comprehensible tornthe end user.
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