Relationship Between Colour Rendering Indices and Subjective Colour Differences

CIE recommends R a and R i as indices of colour rendering properties in CIE13.3. But R a and R i have some problems to be considered. CIE224 was published to solve the problems above. But even the proposed index R f has some technical issues to be considered, and R f is not a replacement of R a neither for the purpose of rating and specification of products nor for regulatory or other minimum performance requirements.