I was doing some more testing yesterday (DK9) and wrote some notes on what I observed:
As already noted - Lightness strength is constant if variable opacity (pen settings) is off i.e. ‘Lightness strength’ doesn’t appear to do anything if pressure sensitivity is off in the main ‘Opacity’ setting.
I noticed in that instance; the main opacity slider appears to have a very small effect on the lightness opacity down to about 10% - then it starts to fade out more noticeably.
I also noticed with colour rate off, the lightness will only display if painting on an already opaque area or layer; It doesn’t show at all on a fully transparent area or layer.
I’m not sure that’s actually a problem; just figuring out what the limitations are and whether there’s any anomalies that shouldn’t be. It’s possible a user could want to apply an impasto texture only on it’s own layer - but that’s not possible with this limitation. There are workarounds for that anyway (e.g. using a mid-grey with an overlay layer).
I’m not sure about the suggestions for the impasto issue - it sounds a bit odd to me. The current implementation might not be ideal, but it does feel quite authentic as noted by @Daishishi - you would expect a brush to leave bristle marks when you work back over painted strokes; and that’s what it does. It spreads out and becomes thinner/less textured as you work back and forth over the laid paint stroke.
As an emulation of real media, I can choose a soft blending brush without lightness to flatten any areas I want to be impasto-free; in a similar way you would pick up a soft dry brush when oil painting.
So - I think it’s good in it’s current state, and mostly feels right when I’m painting. I’m not against what @Voronwe13 is saying though about it being a digital medium; You would ideally expect to have the flexibility to reach zero lightness with the brush if you’ve set those parameters.
By the way - has it already been mentioned somewhere how the current implementation actually works on a fundamental level? I’m curious in case I can think of anything practical that might help.