How do you make a selection within a selection?
Photoshop CS5: If I only wish to select the black portion of the below image (to create a layer mask with it), how would I do so? It was generated by clicking "Make Selection" from a vector shape that's made up of several paths (each of the triangles, then the rectangle that encloses them). Thank you in advance!
As a related follow-up, how do I add to a selection? i.e. If I make one selection, how do I keep adding more parts to it? Necessary to use paths?
The modifiers for selection tools are alt and shift in various combinations. The tool icon will change to reflect the mode (+/-, etc)
make a square selection
hold alt and then select a square within the existing selection (-)
hold shift, add a square (+)
hold alt+shift, select a portion of the existing selection area (x [intersection])
One can ctlr (cmd) click a layer icon in the layers palette to use that as a selection, and the same key modifiers can be applied (with the addition of ctrl).
I frequently store portions of complicated masks as hidden layers for easy mixing and matching while working.