Parametric masks in Darktable - beginners help please!

Very new to proper processing and not up on the jargon, so please be gentle.

The problem is this:

Grey horse, dark background, horse highlights get blown out if I crudely hike exposure. Object is to set up a mask to isolate the horse so I can adjust EV. Complexity, especially when you take mane which is normally more “wind-blown” than in this example into account, makes drawing a mask very very hard.

I’ve seen examples of how to make the technique work but it’s foxing me.

Could someone be a star and try and assume I have the Exposure mode open and am trying to work out which mask settings to start with…channel, opacity…you tell me, because I don’t have a clue :slight_smile:

Or is there an altogether easier way?

What exactly do you want to achieve, make the dark green background lighter? Horse and sky seem to be well exposed for me.

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@dweeble, is this what you want?
432474864999e09f458225da46476ab0a0bb8ed2_2_1035x775.jpeg.xmp (5.1 KB)


I fooled around with L and S (L because horse is bright and Saturation because horse has almost no color. Basically just found out two properties that horse has and used them to isolate it.) parametric masks and then added a drawn mask (because clouds in the sky had those properties too!) to further isolate the horse.

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Thanks guys…Shreedar, thanks for the screenshot, I will play round with those settings tomorrow morning when I’m fresher. Right now my brain is fried! But interesting that it was trial and error which got you there, clealry practice will make perfect…we hope.

PS Shreedhar…sorry about mispelling of yr name.

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If you start typing my name beginning with an @, then the forum will give you choices to select. That way, there is no chance of any misspelling. :wink:

Parametric masks always require a bit of ‘trial and error’. The horse obviously had very little color so (H)ue would not be a good starting point, (L)ightness would be starting point and then try to refine the situation with (S)aturation or ©hromacity. Once you have achieved good coverage of the horse use a simple line mask to eliminate other parts of the image (such as the sky) that you do not want to change.

@shreedhar
I am just learning about masks. I opened your xmp, and learned a lot from it. Thank you.

I am puzzled by the dark clump of leaves to the left of the horses head that is pretty much unselected by the mask. I tried to add a drawn mask to include it, but no matter how I select the settings for polarity and “combine masks,” I can’t just add the leaves to the original selection.

I think I have found the answer to this is that it is not possible.

@Underexposed, why not duplicate the instance and draw a new mask just for that part? It is actually better that way to reverse your process, i case you change your mind. You can name each instance according to the area it targets (horse, clump of leaves, sky etc) so when you open your xmp file again, you will know what each instance is doing.

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I’ll test that. I have another problem now. darktable started overwriting any existing xmp file for an image whenever I try to reopen any image. So I can’t open your xmp. I remember the settings, so I can try out what you said, but I am trying to solve this new problem.

You can make a duplicate of your XMP within darktable and after that you can copy the other XMP file into your image folder.
Then the ‘original’ image is the one you copied and the ‘duplicate’ is your original.
You can delete versions you don’t need within darktable.

@shreedhar, I tried duplicating the instance and drawing a new mask. I also tried a parametric mask using hue as the selection criteria, which did a much better job of picking out just the dark leaves.