I´m experiencing an unfamiliar problem with Photoshop, perhaps a bug.
I´m assembling a lot of panoramas in Photoshop, and this takes a bit of mask tweaking.
For some areas, I use a soft brush in the Layer Masks at ~40% opacity, and heres the problem:
When painting with black at 40% over an area, and then immediately afterwards with a 40% white brush, it takes several passes with the white brush to make up for the one brush stroke with 40% black in the mask. Why is this?
Mathias
#1
Actually, no matter how many times I pass the area with a 40% white brush, the mask never reaches 100% opaqueness. I have to use a 100% white brush to patch the transparency hole.
This is sRGB.
Mathias
#2
It sounds to me like a half-life sort of issue, Mathias. 40% gains could never reach 100%.
#3
Hi Mat,
The best I can achieve with a white brush @ 40% is 1%k after a boatload of strokes. However, as soon as I switch the percentage to 50 or above, I can get 100% white (0%k) with 8 strokes or less. Interestingly, I cannot achieve 100%k by using the 40% opacity black; it tops out at 99%.
What do dis mean, Leon?*
*David Letterman to Leon Spinks, circa 1986.
#4
Mathias,
That's how opacity works in Photoshop (brushes and layers). Each additional stroke is that percentage of the remaining opacity. So, for example, after one 20% stoke, there is 80% transparency left. If you do another stroke, you add 20% of that 80% to the 20% that is there from the first stroke. The math is .2 + [.2 x .8]= .36. For the next stroke, the math would be .36 + [.2 x ..64] = .488 or about 49%. The long version of that formula would be .36 +
[.2 x (1 - .36)] = .488
After 9 strokes with a 20% opacity brush you end up with an opacity of only 87% [.8656].
You can test this with the info palette (stroke a path repeatedly).
-Jay Arraich
#5
That all makes sense.
However, why does it take so many white strokes to make up for one black stroke at the same brush opacity? Its like its not 40% black, but 80% black or similar..
Maybe I´m just not getting it.
Mat
#6