I’m not a color scientist by any measure, so take all this for what it’s worth…
You got me to wondering what a camera’s performance regarding skin tones would look like. I have SSF data for two Arri cameras, one set from rawtoaces and the other from the OpenFilmTools project. Here’s a plot of the Arri D21 from rawtoaces:
Reallly pretty consistent with other other cameras for which I’ve collected data, some of which you can regard here:
https://glenn.pulpitrock.net/openfilmtools_ssf_plots/
So, to consider skin tone presentation, I retrieved the A01 and A01 patch spectra from the ColorChecker reference file, dark skin and light skin respectively. Here’s a quick-n-dirty plot of the values:
Row 2 is dark skin, Row 3 is light. Note that the highest energy in the light skin patch is at >600nm, but that’s where the Arri Red bandpass filter peaks, and falls precipitously after that. Inspecting the other cameras’ plots, same pattern. So, what would it take to “make better” skin tone response? Opening up the right leg of the red bandpass? This is something I’d like to better understand, from a “color mechanic” point of view.