This question was asked here How do I paste into a layer's mask in Photoshop?
but none of the answers work for me! It seems to be a common question on the web, but something is going on with my situation, because absolutely zero of the suggested solutions work.
I'm trying to paste the contents of one layer A into the new layer mask of another layer B, using Photoshop CC on OS X.
I select all of A and press Cmd-C. Then I try any of the following:
Click the "add mask" icon of layer B while the copied image is in the clipboard. I am told this will put it in the mask, but the mask is blank.
Alternatively, add the mask to B first, then click on it, then Cmd-V. This pastes the clipboard into an entirely new layer.
Alternatively, add the mask to B, then click on it, then Shift-Opt-Cmd-V. This does the same thing as Cmd-V.
Alternatively trying any of the Paste Special commands from the Edit menu. These all do the same thing as Cmd-V
EDIT: It occurs to me that maybe the problem has something to do with the fact that layer A is RGB, while masks are grayscale.
EDIT 10/17/2016 This is solved. I am new to the Mac world, and when I read the instruction to Alt-Click, I was doing Cmd-Click, when what I actually needed to do was Opt-Click.