The purpose of this study was to understand CIE (Commission Internationale del Eclairage) Colour Rendering Index (CRI) and its deficiencies. Another aim was to find out limitation of CIE CRI for LEDs. Finally, current works on colour rendering of LEDs was examined in the study. CIE (Commission Internationale del Eclairage) Colour Rendering Index (CRI) is the only internationally recognized colour rendering metric. This metric expresses the colour rendering properties of light sources based on colour shift of test objects when illuminated by reference illuminant and test source. The CIE method to obtain CRI is called CIE test colour (sample) method. Despite of prominence, CIE test colour method has numerous deficiencies. The problems of CIE test colour method became more serious when applied to white light emitting diode based sources. Various studies have indicated that even LEDs with low values of CIE CRI can produce visually appealing, vivid, and natural light. CIE technical committee TC1-62 concluded that the CIE CRI is generally not applicable to predict the colour rendering rank order of white LEDs light sources. The colour quality of light sources is not just a colour difference. Colour discrimination, colour harmony, colour preference, colour acceptability, visual clarity, and brightness are some known dimensions of light source colour quality. For different application different light sources are suitable and relevant dimensions of light source colour quality should be used to select appropriate light sources as per the application. The universal colour rendering metric should be able to define all the dimensions of light source colour quality.
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