Rawtherapee and/or ART and the issue of masks

Hello everyone, I’ve got issues that browsing google for days has thrown no useful answers up for so figured I’d try actually putting my own topic up in hopes of something useful being discovered! It’s an issue I’ve seen discussed a lot, masks in Rawtherapee, but a lot of the time the answers seem either overly technical (and not actually answering the issue, more trying to prove to people that the specific image they’re working on CAN be done if you have an insanely detailed knowledge of the tools whihc is unrealistic for most users) or too vague and ‘yea but no’ is the line.

All I want to do is to be able to use a mask for specific tools (currently noise reduction and sharpening are the ones causing me issues) but nothing I find does the job well.
The basis of my issue is that I want to apply noise reduction to the background and not the subject (so as to not lose the fine details) and sharpening to the subject and not the background (so as to not sharpen things that are meant to be out of focus!)

In ART (the supposed better of the two programs for masking) the local adjustment tools seem to not give you noise reduction as an option to even mask. And in what has until now been my prefered program of Rawtherapee the masking system is ridiculously unintuitive with thousands of things you can adjust but none of them as quick and simple as a brush. I tried darktable as well but their overall interface is incredibly unintuitive and I didn’t get on with it at all so don’t fancy trying to shift my entire workflow to that.

Dealing with Rawtherapee, as that is what I’d like to get it working in, trying to make a mask that targets specifically my subject and not the background based purely on luminance (and the sliders around it which frankly are very confusing) seems an impossible task, there’s pictures that it just doesn’t seem possible and why would it? The idea the subject is always going to be distinct from the background in these values is ridiculous, of course it’s not! But because there’s no simple brush tool to help with just going ‘yep, I want you to include this’ or ‘nope, take this away from that mask’ you’re stuck with a mask that includes either too much or too little.

What are the reasons the developers are SO against the idea of adding a brush tool to simplify the entire process? It’s pretty much the only thing missing from Rawtherapee to make it compete with the real big boys of RAW editing!
The only reasons I’ve seen given seem to boil down to ‘other programs can do that’ and, yes, I can then go on and edit in GIMP for specifics with layers and masks etc, but then I’m working on a jpg so I’m getting a less adjustable image and I’m working on it all AFTER my initial edits when noise reduction and the like should be done earlier in the process. Surely this is an obvious improvement to make to the program which would be of benefit to the majority of users? I rarely run into things that I can’t at least find a workaround for however this one just stumps me. I’m shocked that, given I’ve seen it raised over many years based on the previous people I’ve seen raise it, it hasn’t been sorted by now. Is there any chance a simple brush for masks will be added in the near future or is it a pipe dream?

Local adjustments does offer a spot sharpening tool that has some masking capabilities. It’s not the easiest to use but you can sharpen what you want to sharpen in a mask way, if you want.

I mean, that sounds like you’re just talking about the masking tool I mentioned in my post? Where you have to use the luminance etc values to try and make a mask that targets what you want without being able to simply brush over what you want?

For art, you can use texture boost/sharpening for masked sharpening, and smoothing in mode guided filter and/or non-local means for masked denoising.


I probably didn’t understand/read you post correctly, as my Crohn’s has been acting up. I apologize if I missed it. That said, Darktable has painting/masking under most of it’s tools. I don’t think you can paint in RawTherapee.

Hi Alberto, if I’m remembering my names correctly you’re the creator/developer for ART right? I’ve tried those options (and the sharpening has worked for me!) but I’ve struggled with getting the denoise to work. What are the guided filter and non-local means settings?

I’m curious where you heard this from. No one is against brushes and whatever led you to believe the contrary should be corrected or clarified. The closest I’ve seen is merely an explanation of why it’s not implemented yet.

I think I found the sharpening tool that will work. From the manual, see below. I use the Focus mask first to see what is in focus. The “Sharpening contrast mask” button will match the focus mask and will sharpen from where the “Contrast threshold” is set at. For a poorly foced image I had to set the level pretty. You’ll see exactly what is to be sharpened and what will not be sharpened using the technique.

Contrast Mask

The “contrast threshold” and “blur radius” sliders allow you to control a mask that decides which areas are affected by sharpening and which are left untouched. Activate the “preview the sharpening contrast mask” button Contrastmask-off.png (in the toolbar above the main preview) to see this mask.


Well it depends on the picture, there’s no single configuration that works for everything unfortunately. As a (rough) indication, I would use the global denoise to deal with chroma noise and some luma noise, and then finish up with smoothing where I want a stronger action. Having a specific picture to work with would help though.


I’m not saying that everything is perfect for processing noisy images, which is probably the biggest challenge to solve at the processing level.
It’s not just luminance masks, you can consult the 2 examples on Rawpedia (which do not use all the possibilities - see choice “Advanced”)

and also

But I agree with you, processes to better select the area to be treated (or excluded) would be welcome, whether polygons, Beziers curves or a brush. If it’s not there, it’s not that it’s useless, or deemed not useful, but simply that I don’t know how to do it - it’s largely a GUI problem.


I remember one post (though I don’t have a link as it was a couple days ago I read it) that had some comments that the brush was an inferior option and the other tools were better in the way they targetted things (which made very little sense to me, a brush is the most specific targetting you can get). That post was from a few years ago so a ‘yet’ seems silly because when there’s posts going back to at least 2020 about it, and I’m sure I saw some in the 2010s too, that’s an awful long time for a ‘yet’ over what would be an incredibly useful funtion which has already been implemented to a degree in ART (A fork of the same program)!

I didn’t actually mean what are the figures to use for them, I meant more where do I find them (I might be being blind but I can’t see them) and what do they mean, like what do they do differently?

These are the things I’ve been trying but find they’re inadequate, the shapes you can make with the spots just aren’t precise enough and when I tried to go through all the settings in advance to get a more accurate mask I ran into the problem I stated in my original post, you can’t really target just the subject in most images (the example image of the mouse used felt like a bit of a stooge given the background is just one plain colour nothing like the subject, a relatively easy thing to differentiate!)

Local editing tab → smoothing tool → mode

If you’re activating “Preview ΔE” and fail to get the appropriate “masking” by adjusting scope you can switch it around. Make a Full image spot with generous scope and then add excluding spots to the areas you want to exclude. Remember to move the spots around, both full image and excluding, to control what areas are selected.

I’ve basically never had a situation where these simple moves don’t work.

I’m not sure that it was a developer who wrote that, but even so, the statement is not about opposing the inclusion of a brush tool. While Local Adjustments has been in development for long time, it’s just been a little over a year since it was officially released. Before that, RawTherapee did not have any “serious” local editing capabilities. It is a significant change to what RawTherapee is capable of and is still very much in its infancy.

Keep in mind RawTherapee is maintained by a small team of volunteers (new team members are always welcome!). @jdc is the driving force of Local Adjustments, but as he has written, brushes require lots of work on the GUI and he is not an expert in that area. What we need is someone who has the skills to implement brushes and the motivation to make local editing their top priority. Also, the local editing feature in ART has a completely different lineage, so it’s not so easy to port to RawTherapee.