Layer Mask Logic

[festus]

Hello,
I am wondering what the logic/reasoning is behind the use of layer masks.
Specifically, why, when you apply a mask to an image and you brush it, does the color from the below image appear?
Thanks,
fh

[Ofnuts]

(11-07-2023, 08:23 PM)festus Wrote: Hello,
I am wondering what the logic/reasoning is behind the use of layer masks.
Specifically, why, when you apply a mask to an image and you brush it, does the color from the below image appear?
Thanks,
fh

The layer is a way to edit the layer alpha channel (it can be the alpha channel itself, or a multiplier of the alpha channel). The alpha channel is the layer opacity, so where it is 0 the layer si transparent, and where it it 100% (or 255) the layer is fully opaque, with grays corresponding to partial opacity. When you paint black on the mask it makes the layer transparent.

The advantages over the eraser: the RGB content are not changed. You don't erase, you make things transparent, so you can make them opaque again. Also you can handle the opacity like a color and use the color tools. For instance increasing contrast sharpens edges, or you can create a gradient across the mask to make a layer transparent and so progressively blend with the underlying image.