Arnon

I did some experimentation and I think I have a slightly better preset. It's very close to the one proposed above. As my guide for correctness, I uses a conversion using the LAB color space using curves with both A and B opponent set as a flat 50%, eliminating color and leaving only the luminance channel intact as in the following: In LAB the luminance channel is perceptual. The actual mathematical formula used is quadratic, and cannot be fully replicated by the Black & White filter (I am not sure exactly how it works mathematically, but I have a guess or two based on the fact that any fully saturated single channel gets completely blown out to white slightly above 50%. I then used several reference images - some photographic color calibration images that are typically used for printer calibration, plus some synthetic images I generated to make "slices in the color space". I converted them to B&W using the LAB curves, and then manually played with the Black & white filter to get as close to possible to the luminance from LAB using the Black & White adjustment. For my purposes there was no point to hit an absolute optimal point as what I was after was to get a preset that would get me to a very good starting point that would be basically perceptual, would not suffer from blowing saturated colors to white and from which I can comfortably go ahead and tune an image to my liking. I use it for artistic purposes, not scientific purposes. So here are two presets I ended up with: for reference, here are examples of the difference between the LAB conversion and the Black & White adjustment conversion comparing the default and the preset: Default Black & White adjustment difference from Luminance: Preset 1 Black & White difference from Luminance: