I have a photo and a while ago I had added a layer on top of it which was pure white at 50% opacity.
How can I compensate that effect to get back the original picture?
I have tried adding a black 50% layer, but the picture becomes too dark and there is not enough contrast.
Answer
You can use a levels adjustment layer. I did this in Photoshop but the same technique can be used in other programs.
On the left I applied a 50% opacity white layer to show the effect. On the right I had the 50% effected text layer and then applied a levels adjustment layer.
Note: I moved the white part of the levels slider so the white background would not darken. This makes every pixel to the right of the white slider completely white.
Result
Attribution
Source : Link , Question Author : Community , Answer Author : AndrewH