Hi, Tony.
We have some of what you are looking for:
Flat - we have this, and call it "YC."
Chroma (sometimes labeled "3.58") - we have this too, and call it "Luma."
Low pass would be useful to show an average value for setting midtones, but in digital video we're often looking for the peaks--which won't be visible in low pass--since peaks are what can cause problems.
Robin Sato
Synthetic Aperture