How can I paint with 90% opacity over existing areas on a layer mask without increasing the opacity?

Question

I often run into this frustrating problem when using layer masks.

I have a layer to which I have added a layer mask. Now I select a black brush and paint over it with 90% opacity to hide that part of the layer and reveal the layer below which is grey. If I now paint again over the same area using the same brush, the effect sort of adds up and I now see that area as black instead of grey.

Is there any way at all that I can avoid this? Is there any setting with which the brush will not paint the part that I have already painted?

Answer 1

Rather than using opacity of the brush, you should choose shades of gray for your brushes. That way overlapped strokes will not add up and get darker.

You can also use "Lighten" and "Darken" blend modes on those brushes to avoid messing up other parts of the mask

For example, let's say you painted part of the mask with pure black, and it's just how you want it. Now you want to paint some of the rest of the mask with an 80% gray colour. Set the blend mode of the gray brush to Darken, and it will darken anything you paint on that is still white (or ligher gray) but will not affect any parts of the mask that are black (or darker than 80% gray)

If you've already done it another way and have a few dark patches you want to fix up, select the color you want with the eye dropper and then paint that color over the darker areas you didn't want darker.

If there are harsh boundaries between light and dark, you could even try blurring the mask with gaussian blur to smooth the transition.

Answer 2

First, always make sure you are painting the mask, and not the layer.

So remember with layer masks, black in the mask = 100% transparent. Any level of gray between equals that much transparency.

You can always paint the mask with 100% black, and then go to the masks palette and turn the opacity of the actual mask down to 90% (see below)

If you cannot find the masks palette in your current interface, go to Window > Masks.

Another way to accomplish this is to just use your brush set to 100% opacity and use #414042 instead of solid black to paint in the mask.

Answer 3

Can't you paint with opaque layer, 90% gray instead of semitransparent layer and black?

EDIT: what I meant is that instead of using a black brush with 90% opacity, use 90% gray brush (following your comment I understand that the opacity is applied to the brush rather than the layer, but the same advice holds here). With the black brush, multiple strokes on the same place essentially change the color (90% x 90% etc.). With the opaque gray brush, the subsequent stroke is not additive, but rather replaces the previous color, but in this case the new color is the same as the old one so you end up with the pixels unchanged.