Hi,

I also do a lot of still photography and mainly use darktable for post. In darktable there is a filter called color zones. Basically, it shows the color spectrum on the x-axis and allows adjusting of lightness, saturation and hue per color band. That way, you can e.g. massively intensify a blue sky without pulling the saturation of the whole image up.

Would something like this be achievable with existing MLT/frei0r filters?

-S

Have a look at the effects in the colour correction group https://userbase.kde.org/Kdenlive/Manua ... Correction

Maybe the curves https://userbase.kde.org/Kdenlive/Manua ... ion/Curves filter

Yeah, I thought about the curves but it's very hard to get a similar effect with those. That colorzones filter in darktable is just brilliant...

While I'm loving the curves frei0r is really lacking color grading filters such as the one you describe. In particular, such a single filter would allow to grade according to the six "main" colors more easily: saturation and "brightness" (quotes on purpose). We even have such a filter in The Gimp ... and it ain't known for doing useless filters.

If you can give a more precise specification of how this filter works then we could file a feature request with MLT or frei0r.

Well, I'm no expert in describing this stuff but check this out:

http://www.darktable.org/usermanual/ch0 ... olor_zones
https://plus.google.com/photos/+ArielKa ... 3724325345



You choose one of the tabs and then pull a node up or down which will increase or decrease saturation or lightness for this color band or modify hue, depending on the tab you selected. You can also move a node horizontally to adjust it more precisely to the band you want to modify.

Thanks for the pointers, I now understand better. So this is controlling luma and saturation according to hue. Controlling hue on hue is already available through the curves effect. For instance, Gimp basically uses six instead of seven (the eight corresponds with the first) control points; one for each RGBCMY. I've asked on the MLT website about such an effect and where exactly I could place such a feature request.

If you don't have it, I recommend installing darktable. There's ready repos/ppas for the major distros and if you also shoot photos every once in a while, it's a massively useful tool!

I am on the MLT mailing list and Brian Matherly recently wrote an NDVI postprocessor for frei0r on my suggestion. I was thinking on posting another suggestion there but first I wanted to check if there's any way to achieve this with existing tools.