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Lift and Gain in LumaLiftGainGamma effect are always zero

LootHunter
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Hello.

Recently I've decided to learn video editing a bit and kdenlive looked like good tool to do that. So, I'm working through tutorials now. Well, long story short - when I add LumaLiftGainGamma to the video clip, I can't change Lift and Gain parameters. Changing Gamma works - both typing and dragging the bar, but LIft and Gain always stuck at 0,000.

I'm using the last 19.11.80 version on Windows 10.

Are they locked somehow and I have to do something? Or is this a bug?
mickae
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hello,
yes, it is a bug and has already been reported.
But there is one consolation: If you want to use lift/gamma/gain, you can't move the colours in the colour wheel in lift only, in gamma and gain it works. And in Lift you can still move the values: You only have to click with the mouse on the R or G or B value and then move it up or down with the mouse wheel. Don't be irritated by the dot in the colour wheel, it jumps somewhere. Otherwise, the filter "Lift/gamma/gain" is very important and a great help in adjusting colours.
mickae
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Hello to the developers,
please fix this important filter: Lift/gamma/gain. Every video editing software has this central effect - all professionals I know use exactly this tool.
Please fix.
Where is the best place to make this request?
berndmj
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mickae wrote:Hello to the developers,
please fix this important filter: Lift/gamma/gain. Every video editing software has this central effect - all professionals I know use exactly this tool.
Please fix.
Where is the best place to make this request?

Works for me in kdenlive 21.12.0 (latest version) on Windows 11. Will check later on Linux ;-)
mickae
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Hello brendmj,
thank you for your efforts. I will now describe the error in a little more detail:
Lift/gamma/gain does not work properly. Not even in the current Kdenlive version 21.12.0, neither on Manjaro Linux nor on Windows 10.
If you move the center point in the color circle of Lift with the mouse, nothing happens. With gamma and gain the color is moved with the center point in the color circle exactly as expected. But this function is the normal operation, also with other programs.
With Kdenlive you can only change the values for Lift, if you change the underlying numbers for R, G or B, then the center point will also shift a little bit.
The same error also occurs in the AppImage.

My question: If this abnormality is probably the case for everyone, I suspect that lift/gamma/gain is not used that often. What do you use for your color grading or correction?
berndmj
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Ok, so I tinkered with it a little bit. First off, I am not a color grading expert.

My understanding is this: Lift applies to the shadows, Gamma to the mid-tones , and Gain to the highlights of any given image. That is what the vertical sliders do: If I slide them up or down I lighten or darken the respective areas. If I want to do the lightening or darkening only for certain colors I move the center of the color wheel accordingly.

When moving the dot in the color wheel of Lift, nothing happens. Agreed. But what should change if the vertical slider stays where it is? Only when I move it should the image change, right? But this is where the effect indeed behaves erratically because when I move the slider up or down the dot jumps around like crazy changing the hue (coloring?) of the image. So there is something wrong.

Interestingly, once I moved the slider for Lift I can move the dot and the image changes accordingly. Also, entering values directly behaves strangely: I cannot overwrite or delete like expected. And, I would expect the sliders to be all in the same position and the RGB values the same when using the effect for the first time or after a reset but Lift shows RGB @ 0, Gamma @ 1, and Gain @ 1 with the slider at the lower quarter of the scale.

Since you need the effect to work properly and seem to know the subject matter I suggest you log a bug @ https://bugs.kde.org or an issue @ https://invent.kde.org/multimedia/kdenlive/-/issues.
mickae
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Hello brendmj,
great that you can also find the error. I am not the only one with my computers.
Of course you can lighten or darken the shadows with the slider. But "Lift gamma gain" is mainly responsible for color correction.
If I'm only concerned with brightness, I always use "Levels" to set the black point, the white point and possibly also the gamma.

Do you know how to report the bug correctly? I think I've done that before, but it's a horror for me to bite my way through it.
I looked at both of your links - and immediately clicked away. I do not understand all this. I would have to have everything translated first and hope to still have energy to understand something.
If you have the strength to help me there very gladly, that would be great.
By the way, with Shotcut, which also has an almost identical tool, everything works as expected. Both have as a basis this MLT.

Translated with http://www.DeepL.com/Translator (free version)

I have now reported a bug, I am curious what happens and if I did it right.
berndmj
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mickae wrote:I have now reported a bug, I am curious what happens and if I did it right.

You have done well!

I have added a screen recording to your bug report (https://bugs.kde.org/show_bug.cgi?id=447948).
mickae
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Hallo Bernd,
thank you very much for the support. I really hope that Kdenlive will continue to develop and soon really become a very good, professional video editor for Linux.
Danke
mickae

 
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