play raw: mask and darken sky

I would like to develop a nice Darktable workflow for masking and then darkening skies which are overexposed relative to the main content.

An example I find difficult is shown here. The composition is unremarkable, it was chosen to highlight the issue (the lens has some CA, and the leaves are difficult to separate). What would you use?

Just to emphasize, I am primarily looking for masking solutions, and then an exposure correction. I find the tone equalizer tricky to use in this context, but if you prefer that it is fine too.

P1005231.RW2.xmp (10.0 KB)
P1005231.RW2 (23.1 MB)

These files are licensed Creative Commons, By-Attribution, Share-Alike.


I’m no expert at this, but maybe it’s a little more dramatic. dt 4.6.1. I didn’t try to do a full edit, I just played with the tones in the sky, mostly with ColorBalanceRGB.

P1005231.RW2.xmp (8.6 KB)

1 Like

Thanks, but the artifacts around the leaves you get are exactly what I am trying to avoid.

1 Like

Would this be dark enough? It is a mask on exposure that did the trick. The other changes are only to improve the picture.

P1005231.RW2.xmp (14 KB)

1 Like

Thanks, but just to clarify: I am looking for solutions without artifacts.

I’m afraid you’re going to have a hard time; without any masking and exposure manipulation, the CA around the leaves is so strong, that with corrections it creates an effect which resembles ‘ringing’. At least I think it’s CA.



Very hard because of the high contrast between the sky and the leaves + strong CA at the interface
I tried to stick to your conditions and only used a masked exposure instance with a basic pipeline,
I think if I reduce the exposure further in the highlight too many artifacts start to appear

P1005231.RW2.xmp (15.9 KB)

1 Like

Again, masked exposure adjustment is precisely what I am after.

But I am interested in other approaches too!

I think that is why the tone eq works much better… use the exposure compensation to move the mask to give you lots of room in the highlights and then just drag down from the right most node… its usually the best results… as for the CA if the raw CA correction, the CA module or lens correction still cant master it…you can use CC module gray tab…set on blue and masked with the details slider then reduce the opacity slowly…you can often fade that in … I can’t take a run at demonstrating this until later when I have access to DT but it should be possible maybe even try the colorfulness and drop the blue or blue/red with a details mask on those edges…

1 Like

Tone EQ is basically masked exposure. Here’s an attempt with the ‘linear’ compression from Boris’s video:
P1005231.RW2.xmp (15.7 KB)

P1005231_02.RW2.xmp (19.3 KB)

A close-up from one of them:


I think the main problem is, that there are parts of the sky which are burned out. Darkening the sky is leading to an emphasis of these parts. The CAs doesn’t make it easy, but are in my eyes less a problem, if you are willing to accept them. They are in the end already in the original RAW.

P1005231.RW2.xmp (19.8 KB)

I usually would edit the pic like that. But you asked for. :slightly_smiling_face:


My version…

P1005231.RW2.xmp (21.1 KB)

1 Like

I would not darken the sky too much because this gives an unnatural appearance. My attempt without local masking.

P1005231.RW2.xmp (11.5 KB)

darktable 4.6.1

P1005231_02.RW2.xmp (15.0 KB)


P1005231.RW2.xmp (12.9 KB)


Trying with RT dev and local editing. Some artefacts are visible

P1005231_RT.jpg.out.pp3 (19.6 KB)

Here’s a mask made with the GIMP color>threshold function after opening the raw in RawDigger:

After applying a 2.5px Gaussian blur to the mask, the GIMP gave me this after an adjustment or two:

“CA halos” not too obvious when viewed to f ill my screen.
Posted FWIW …

No exposure masking just the tone eq… I used a second instance in the blue channel to tweak the sky a bit…

Edit with no Tone eq

With tone eq turned on…

With all that dynamic range and blown areas in the sky personally I think the tone eq with its mask and curve will work much nicer than a masked instance of exposure applying the same correction to all pixels… in this case I often use rgb sum for the mask and I check the old guided filter as it sometimes can provide a bit more punch…

P1005231.RW2.xmp (17.6 KB)

Though just for kicks a very quick parametric mask and dropped exposure instance wasn’t bad zoomed out…

P1005231.RW2.xmp (25.4 KB)


Hi, not a Darktable user but, I’d like to suggest approaching this a bit differently. Instead of trying to darken the sky with a complicated mask, you might find it a lot easier to avoid the inevitable artifact issues by initially adjusting the image for the sky, and then bringing everything else up to where is needs to be. A much softer and less precise mask can be used to selectively bring up the general brightness around the sky without suffering too many unintended consequences. I know non-freeware is generally verboten (feel free to delete the image if there’s a problem with it), but here’s about a minute in Lightroom using the simple methodology above. it would look a whole lot better if the sky wasn’t significantly blown in the RAW file…

1 Like

Here is my second stab at it. Have managed to reduce the artefacts and yet managed to darken the sky. Essentially played with the exposure and the localised brilliance. Having said that, reducing the artefacts around the leaves, completely seems to be a VERY tall order

P1005231.RW2.xmp (16.4 KB)

1 Like