local contrast tool feedback


I have tried the latest dev version including the local contrast tool and I think it is a great tool!
Thanks :grinning:

I noticed that it is a perfect addition to the shadow/highlights tool. Example given:
Raising shadows with the latter somewhat flattens the affected area. With the local contrast tool I can now bring back of the some so called “pop” in those areas.

Playing around with it also lead me to an idea. Would it be possible to add an option that allows to make the local contrast tool work only on the areas affected by the shadows highlights tool?
This way we could bring back local contrast in those areas without affecting the other areas. this could be done by a check or something like that.

(Alberto) #2

hi @McCap, thanks for the feedback!

I think it should be possible in principle, but I haven’t checked how the s/h tool works. however, the fate of the s/h tool is uncertain at this point, for many people it does more harm than good in many cases, and we are discussing whether to get rid of it completely…



Admittedly, I rarely used it myseslf. There’s other tools which do the job better, like wavelets or retinex…Which is also the reason why I asked some months ago what is behind the s/h tool.

Out of curiosity, Is the local contrast tool based on unsharp masks?

(Alberto) #4

Yes, USM with large radius essentially


After some more playing with this tool I am guessing that the darknesss and lightness levels are basically what I did in this tutorial with the curves on the detail masks.

This also leads me to two suggestions:

  1. Add a selectable luminance range for this tool, like in the wavelets contrast tool.

  2. Maybe allow for more than one instance of the local contrast tool. This way you could do what I did in above mentioned tutorial and you could also add contrast on different scales. How to implement this I dont know exactly. Multiple local contrast tools would just look stupid. Something like in the local lab version, where you can select a number of control points would be good. In this case I don’t think that more than two or three instances of this tool would make any sense. The advantage of this over CbD or wavelets contrast (where I already have multiple levels) is that one could make instances work on different luminosity ranges and the ability to fine tune darkness and lightness makes it much more controllable.

What do you think?


I hope the shadows/highlight tool stays. It has done me much good and no harm I know of. I almost always keep the sliders at small values, often one of them at 0. I often go back and forth between Shadows and the Black slider. S/h is a convenient, effective tool. Sometimes you want to work on the Lab-L curve, sometimes you want to use sliders, sometimes both.

(Gord) #7


(Alberto) #8

Thanks for the feedback. Regarding multiple instances/local editing, my opinion is that we want to do this right and find a solution that is general enough to work for the whole of RT. I’m not interested in hacking something tool-specific at this point… (other people might have different views though)

(Alberto) #9

Fair enough. If people find it useful, I suppose it will stay (though it’s not up to me to decide…)

(Alberto) #10


(Gord) #11

Sorry, it would have been better if I had expressed myself more like @RTCharles. It was late, I was tired, but I should be better than that

I think the shadows/highlights tool can be useful, and I think that if it is removed it will become apparent that many users will be upset by its removal, at which point the maintainers would find themselves embroiled in controversy.

(Morgan Hardwood) #12

I use S/H as well, also at low values.


I understand from @Morgan_Hardwood’s reply to the local lab thread that you are busy cleaning and restructuring RT, which is great!
It also makes sense that things like the ones I suggested be implented or not once it is decided how local lab will work in the future as my suggestions would very well fit into a local lab version.

So thanks for all your (and @heckflosse and @floessie and all the others), for your hard work.
I’m looking forward to the things to come and will occasionally make random suggestions when an inspiration particle hits my brain. :wink:


Yes, of course it can be useful, but only to some extent. I wouldn’t remove that unless there was something better on the horizon. Now, it produces haloish effects and often must be used in conjunction with different tools, which isn’t obvious.

(Alberto) #15

actually, right now we are busy cleaning things up for the upcoming 5.4 release, which will have a ton of cool* and useful* new features. after that, then, the plan is to rework the internals to accommodate (also) for local editing…

*YMMV, of course :slight_smile: