Position Paper: Changing the Colour Metrics?

The quality of light plays a key role in determining how naturally, vividly, and reliably we perceive colors. For decades, the Color Rendering Index (CRI) or R_a has been the primary metric used for this purpose and is well established in standards, product information, and lighting projects.

This position paper analyses introduction of R_f as a replacement for CRI, as proposed by the International Commission on Illumination (CIE) and recommended in CIE PS 002:2025. A SWOT analysis is used to systematically evaluate the opportunities, challenges, and potential risks of such a transition. 

As a result, the introduction of R_f as a replacement for R_a is fundamentally rejected due to the significant risks identified.

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