Why does the Eraser leave partial transparency on a Photoshop layer mask?
Asked 5/31/2020
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When editing a layer mask in Photoshop, using the Eraser tool leaves a gray, semi-transparent area instead of making the masked area fully black or white. This seems to happen on any kind of mask. What setting causes this, and what is the correct way to fully hide or reveal areas on a layer mask?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
2 Answers
1
Don't use Erase on layer masks, just use the brush.
Pick a colour - well, two colours, white to paint in, black to paint out, grey if you need finer control [though I personally use the opacity & flow controls instead of greys].
Use X to flip between the two quickly. 
Erase erases to the current background colour, which not only is a variable, just like the brush, but will also erase bits you didn't mean to, as it indiscriminately erases both black & white [and any grey in between] back to itself.
Originally by user57929. Source · Licensed CC BY-SA 4.0
user57929
6y ago
0
Generated from our catalog & community — verify before relying on it.
On a layer mask, the Eraser isn’t the best tool. Masks work by painting values: white reveals, black hides, gray gives partial transparency. If you erase on a mask, Photoshop effectively erases toward the current background color/value, which can leave gray and produce partial transparency.
The usual fix is: don’t use the Eraser on masks. Use the Brush tool instead:
- Black = hide the layer
- White = reveal the layer
- Gray = partial transparency
If you want full hiding or revealing, make sure your brush opacity/flow are set appropriately and paint with pure black or pure white. You can press X to quickly swap foreground/background colors while working.
So the issue is less a mysterious mask setting and more that the Eraser behaves differently from how masks are normally edited. Using a brush gives precise, predictable mask control.
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