Regarding the SOTS 35mm reference to 16mm target … I noticed that all matching/prediction attempts produced colorized tree-trunk shadows for the 16mm. (Such poor distributions are allot easier when viewed on the LCD screen I’m using, simply by changing my head position – never before thought of that as a plus.) I’ve come across something similar when using HSL color transferring between same pictures.

When the L (lightness) of the 2 pictures have differences (contrast, brightness), the transferred HS (hue,saturation) “colors” are altered by the destination’s different L, and sometimes unacceptably so. I’ve found that pre-matching the lightness of the destination to the source (very easy to do on the B&W L splits) produces a proper color transfer result.

Enough of your excellent matches show such anomalies that they cause you constant push-here-pull-there touch ups. Would some sort of R-G-B pre-normalization step, to create a better distribution for your limited samplings, save you such re-adjustments? (I would suggest using a larger sample pool, but the increased storage and processing requirements for such diminishing returns might be prohibitive.)