I color corrected same frame in both Kdenlive and DaVinci Resolve using only one instance of HSL Primaries (Hue Shift, and Saturation scale parameters only), in DaVinci Resolve using Hue vs Hue and Hue vs Saturation curves. I matched every color to fit in the right position on vectorscope, but I get significantly different visual results for Blue color. You can see 100% crops below
What is more confusing is that, when i import that DaVinci crop into a Kdenlive, vectorscope reads “correct/same” value for the blues. Here are the vectorscopes:
When I imported DaVinci crop, it did not change color or something due to mismatch of colorspace or something. Both samples looked the same as in the first screenshot i sent, but vectorscope reads them as the same.
One on the left is from DaVinci, on the right is a Kdenlive. I will research more about it, and try different Gamma options in DaVinci to se if there is a match that will lead to explanation.
On the other hand when correct lightness of the colors in HSL Primaries to match on waveform I get good visual match too:
I’ve continued my testing and have determined that this issue is not related to the Color Profile/Gamma settings in DaVinci Resolve.
The waveform looks the same on both pieces of software when the footage is not color corrected. However, when you start moving the Hue Shift sliders in HSL Primaries in Kdenlive, it also affects the luminance, which is visible as change on the waveform monitor. In contrast, when you adjust the Hue vs. Hue in DaVinci Resolve, the waveform does not change.
I also checked the behavior in Shotcut, and it’s the same as in Kdenlive, a change in hue also changes the luminance. I suspect this is an issue at the effect / filter level, and I don’t know how difficult it would be to change.
That’s most likely not something we can solve. Effects/filters are provided by frei0r and avfilter libraries, so you would need to contact their maintainers if something doesn’t work as it should.
For HSL Primaries, yes MLT is the source of that effect. The scopes are implemented in kdenlive directly, so if you find issues with them, that is (probably) our problem (unless it’s in turn something they use that we don’t directly maintain ; ).
For other effects, there could be other maintainers that need to be contacted. They fall under a few different plugin umbrellas, but may not in turn be directly maintained by those umbrella organisations.
