till now I did color correction with the bezier curves, usually quite simple just by using one or two curves for luma and a color and then applying another effect for saturation and the results i m very happy with.

the question is: how do people usually use the Lift / Gamma / Gain effect? do you have a specific way / workflow advice for me or maybe there s a link to a general tutorial how to use this effect? I saw the same thing in shotcut and other video editors , but I couldnt find a proper advice on how to use this tool. how is this generally called? Thanks

I'm a "Curves-guy" myself and still prefer that way of working.....although I'm not that adept with Bezier handles.

The Lift-Gamma-Gain effect/tool is really just another approach to manipulating the curves via the HSL (Hue-Saturation-Luminance) color model.

https://en.wikipedia.org/wiki/HSL_and_HSV

So with this effect you have three sets of color wheels (controlling hue and saturation) and levels sliders (luminance/lightness) each for controlling Lift (Shadows/Black point), Gamma (Mid-tones) and Gain (Highlights/White point). Like any color correction tool, to use it properly you really need to monitor adjustments with the support of the videoscopes - WFM, RGB Parade or Histogram if you prefer, and sometimes Vectorscope, especially for skin tones - unless you are comfortable eye-balling it.

This article by guru colorist Alexis Van Hurkman gives a very helpful overview of the somewhat confusing terminology that surrounds color correction tools as they are applied in different software.

http://www.provideocoalition.com/whats-in-a-name

As for tutorials, I couldn't find anything specifically for KDenLive, and I'm new to it myself. There are a couple of videos on YouTube that demonstrate the basic principles of Lift-Gamma-Gain. This one (using Adobe Speed Grade) I found especially clear and applicable to the LGG effect as it is provided in KDenLive:

https://www.youtube.com/watch?v=aHABKXpinVU

Presented by Andrew Devis I think. Really like his CC tutorials. Note that there it's called Offset-Gamma-Gain - see what I mean about the terminology ?

Hope that helps.

Edit: I know you didn't ask about, but in this context it's probably also worth mentioning the SOP effect:

https://userbase.kde.org/Kdenlive/Manua ... on/SOP/Sat

There, you are basically doing the same thing, but manipulating the individual R,G,B channels curves directly through the Offset (=Lift), Power (=Gamma), Slope (=Gain) controls, plus Saturation control. That confusing terminology thing again ! If you are used to using RGB curves, you might find that approach more familiar/intuitive, again with the aid of the scopes. Personally, I don't like nudging numbers.

Oh, yes, and of course there are also the Bezier Hue, Saturation and Luma curves if you are familiar with using them...me not, apart from tinkering with the Saturation curve to experiment with 'vibrance' control. But together they constitute a curves equivalent of the (HSL) Lift-Gamma-Gain effect/tool, although I'm still not sure if the Bezier 'Luma' curve there actually represents (HSL) 'Lightness' or (YCbCr) 'Luma' values (not the same). Maybe should look at that. Anyone know?

@ Inapickle wonderful, thank you so much for these articles!!

learning (and seeing i m not the only one confused by all these names etc... ) a lot of things today, thanks again!

looks like i ll stay also with the curves for now like i feel comfortably with them and it seems easier / faster for me to apply the look i want.

what i m concerned now a little bit while tuning the colors is the propierties I can adjust of the clips (maybe i should open a new thread for this?):

I can choose a colorspace and also "full luma range". When I render a video that will be played back later in a cinema via digital projection, I m not sure what makes sense here. Also: when i dont toggle "full luma range", is the range automatically limited to a certain level?

You see i m very much in the beginning of understanding all this color stuff

kalimerox wrote:@ Inapickle wonderful, thank you so much for these articles!!

You're welcome. Needless to say there's a wealth of information on color correction and grading out there on the web, from beginner to advanced.

It pays to grasp the basic color theory behind these tools, but IMHO the best way to get acquainted with them is to put a suitable color reference chart on the timeline, open up the video-scopes and push the controls around, seeing how they affect the luminance and channel (parade) waveforms and watching the color changes on the chart - you'd soon get a feel for how the LGG color wheels work. Here's a chart that I use a lot for reference, conveniently resized to 1920x1080:

http://i.imgur.com/VhP96Ks.jpg

You can find the original DQ-Tool reference charts for download here:

http://www.photoindustrie-verband.de/dq-tool

kalimerox wrote: I can choose a colorspace and also "full luma range". When I render a video that will be played back later in a cinema via digital projection, I m not sure what makes sense here. Also: when i dont toggle "full luma range", is the range automatically limited to a certain level?

Not exactly sure what you're asking here. If, as I suspect, you are referring to the "full luma range" flag option in the advanced clip properties, this description in the KDL Manual explains it pretty well:

https://userbase.kde.org/Kdenlive/Manual/Full_Luma/en

If it is that and, after reading the description, you're still not clear about what it does and the implications for editing your video sources, it would be helpful to know what your source video is/recorded on, and the native luma range.

Thank you again for these links and advices!

I m on it practiciing and will go deepter into the kdenlive manual before asking more questions

My source material is from a sony a7s, recorded in 25 p with different picture profiles, but usually with a cine gama and a lot of low light recordings but also daylight. As i understand from the article, toggling the full luma range option would just make sense for me if I export the files to work on it with another grading tool etc (which i m not gonna do.). so as soon as i do color grading in kdenlive i shouldnt click "full luma range"...
but what i thought i d do for some clips is: align audio and video and render out in lossless h264 to reimport into kdenlive for color grading. in this case it would make sense, right?

Thanks for all these advices, I just imported the chart into kdenlive and wil start playing a bit with it...

I'd like to able to advise you on this, but other members who actually own a Sony a7s would likely be in a better position to do so. For one thing, you do not say what the native (YUV) luma range of your source clips is. Also, having gone on to perform some further tests I find myself a bit at odds with some of the statements in that description of the "full luma range" option as it applies to my own workflow, and that I need to work through.

Suffice it to say that it does pay to know and/or examine the (YUV) luma ranges of your inputs and outputs, and especially if you intend to use an intermediate format for your processing. For now, I do that by bringing the files into Windows and examining the YUV histograms and values with AVISynth filters (Histogram and ColorYUV). In Linux the same could be done with AVISynth and VirtualDub via Wine. I'm checking that out just now.

http://www.garratt.info/blog/making-videos/

There maybe be other tools, like VapourSynth, which has it's own port of the AVISynth Histogram filter but I haven't tried it. I'm still getting familiar with the linux environment.

Still I hope the information I provided on Lift-Gamma-Gain was helpful, at least.

Cheers.

@Inapickle: thank you very much with the useful information you are posting here!

I'm still not completely clear myself how to deal with different luma ranges. In video projects I'm doing in my day job (I'm not a video pro at all, video is just a pet tool to this interesting new channel for conveying knowledge) I often have mixed sources: real-life video recorded on a Prosumer Canon HF G30 in H.264, and then HDMI recordings from a Surface tablet screen. While no-one probably notices any problems here, I would like to better understand the overall processing pipeline.

When I was yonger, I was under the impression that going digital would solve a lot of problems. Now I'm slightly wiser in that I have seen so many instances of "the problems just change, but never get less".

I have a Canon HF-G10 myself, which like the HF-G30 records with an effective 16-255 luma range. I don't and have never owned a DSLR with video capability. Nearest to it, if it counts, is a Nikon AW120 'all weather' camera, that shoots 1080/30p mp4 with full scale 0-255 luma.

I'll come back on some of the things I've discovered about the implications of selecting the "full luma range" option when processing native clips off the HF-G10 and AW120, and the various transcode intermediates. I'm a bit tied up today.

Take your time. I would like to ask you to open a new separate discussion thread on your findings re full luma range. Thank you very much for this interesting discussion.

yes, thank you guys! very good infos here! and good idea to open up a new thread about the Luma range etc.. think this whole topic is interesting for a lot of people.

Et Voila !

https://forum.kde.org/viewtopic.php?f=272&t=130641&p=349799#p349799