
Recently, a theoretical framework was presented for designing colored filters called Locus Filters. Locus filters are designed so that any Wien-Planckian light, post filtering, is mapped to another Wien-Planckian light. Moreover, it was also shown that only filters designed according to the locus filter framework have this locus-to-locus mapping property. In this paper, we investigate how locus filters work in the real world. We make two main contributions. First, for daylights, we introduce a new daylight locus with respect to which a locus filter always maps a daylight to another daylight (and their correlated color temperature maps in analogy to the Wien-Planckian temperatures). Importantly, we show that our new locus is close to the standard daylight locus (but has a simpler and more elegant formalism). Secondly, we evaluate the extent to which some commercially available light balancing and color correction filters behave like locus filters.
Rada Deeb, Graham D. Finlayson, Elaheh Daneshvar, "Locus Filters: Theory and Application" in Color and Imaging Conference, 2023, pp 1 - 11, https://doi.org/10.2352/J.ImagingSci.Technol.2023.67.5.050407