Impact analysis of introducing cone-fundamental-based photometric system in units and metrological applications

Cone-fundamental-based photometry has garnered attention for its ability to provide better representation for quantifying visual sensation. Recently, the CIE and Consultative Committee for Photometry and Radiometry (CCPR) have started considering the possibility of adopting a revised spectral luminous efficiency function, V F ( λ ), based on the CIE cone fundamentals, as a standard function to derive photometric quantities, instead of the current V ( λ ). While adopting a scientifically more rigorous photometric function in the SI is quite important, there is significant controversy surrounding the proposal to replace the current function with revised ones. To support discussion on the applicability of the revised functions for future photometry, two types of analysis were conducted; one examining the potential change in photometric values and the other assessing an instrument quality index to evaluate the impact of replacing the standard photometric function V ( λ ). The results showed that the discontinuity of photometric values, caused by the differences between the photometric functions, was wavelength-dependent and could not be fully compensated by modifying the definition of the base SI unit. The replacement of the current function with revised ones also causes inconsistencies in the qualification of photometric instruments, leading to the conclusion that the potential changes from this replacement are not negligible from a metrological point of view.