Brushes's blend mode reset on transparency mask

Im not an experienced user.
So I have a paint layer and its transparency mask that I set in isolate mode to see it.
The problem is that when I select the “adjust dodge” brush, and try to paint with it on the transparency mask, its blend mode has not the dodge effect. Worse, it reset to normal. I don’t even have to paint with it to reset it :
While on the transparency mask, just filter brushes by “fx”, select the dodge, select the lighten, then reselect the dodge. they both reset their blend mode to normal. That doesn’t looks very expected.
Am I doing it wrong ? Can’t dodge on transparency mask ? Serious Bug ?

The purpose of a transparency mask is to paint the mask either black or white or any lightness in between.
Painting black on the mask will make the layer the mask is attached to transparent in the black areas.

Using blending modes with masks is pointless unless I misunderstand what you mean?

Transparency masks only take into account lumetri or lightness values, for example painting on a transparency mask with 50 Percent grey will result in the layer attached to the mask being 50 percent transparent in that area.

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It seems that you can’t but this may not be a bug.
You can use the various blending modes on a Greyscale colour profile image but a transparency mask seems to be different.

You could paint on a paint layer to get the blending effects you want and then convert the paint layer to a transparency mask:
Right-click on layer → Convert → to Transparency Mask

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I just want to lighten/dodge area of the mask like if it was a black and white paint layer, and see the result in real time on the upper layer. That should not be a problem at first thought ?

Any method that could allow real time visual of the upper paint layer while making some lighten/dodge effect on its mask ?

Not that I’m aware of.
All you can do on a transparency mask is paint a shade of grey on it.
You can also use filters on it but they affect all of it.

There is a ‘trick’ you can do where you put an ‘imitation’ transparency mask over a layer and set the imitation mask to Erase blending mode.
You need to group the imitation mask and the paint layer to limit the layer stack range of the Erase blending mode.
Then, you can do whatever you want on the imitation transparency mask (which is really a paint layer with an ‘erasing’ effect on the layer below it).

Edit Add: That only works if you manipulate the opacity of the ‘imitation’ mask so it’s a more than a bit weird.

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this sound like a good idea, but can’t figure out how to make it works, even when manipulating the erase layer opacity. I tried like this :
A group layer with in it :

  • erase layer on top, that is a black and white paint layer with erase blend mode.
  • the paint layer at bottom with normal blend mode. (image that I want to mask some part)

With hindsight, it’s not a good trick at all since it doesn’t do what you want.
Essentially, you can’t do what you want to do because of the limitations of what can be done with a transparency mask.
However, the transparency mask does what it’s intended to do.

If you want this capability for a transparency mask then you need to start a topic in the Feature Requests category where you explain what you would like, how it would work and example work flows and images.

I suspect that the transparency mask has built in limitations that would make this difficult or impossible.

yes, in erase blend mode, the limitation is exactly the same as transparency mode.
And I still don’t understand how to use a simple erase blend mode on a layer. It has simply no visible effect.

It was a terrible idea but here is an example of Erase layer blending mode in use. Different opacities used on the Erasing Layer: