Intersecting Two Selections in Photoshop

What happens when you press the Shift and Alt (Option on the Mac) keys together? Not a collision, but an intersection. Pressing both keys while dragging with a Lasso or Marquee tool or clicking with the Magic Wand tool creates the intersection of the original selection with the second selection.

To retain only the part of an image where two selections overlap, press Shift and Alt (or Shift and Option on the Mac) and then drag.

You can select a portion of an image with a tool such as the Polygon Lasso tool. Then press the Shift and Alt (Option on the Mac) keys at the same time and drag with the Rectangular Marquee tool.

Getting the Keys to Behave
Photoshop has a little glitch in its way of doing things. Well, not so much of a glitch as a conflict.
With so many ways of doing things with Photoshop, it’s no wonder that somewhere along the line you have to jigger with Photoshop to get it to do what you want. For example, how does Photoshop know whether you want to create a perfect square or add to a selection when you press the Shift key?

Let me lay this out for you:
-When you make an initial selection with the Rectangular or Elliptical Marquee tool, pressing the Shift key constrains the proportions of the selection, thereby allowing you to create a perfect square or a perfect circle.

-If you press Alt (Option on the Mac) with either of these tools, you can draw from the center out.

-If you press Alt (Option on the Mac) with the Lasso tool, the Lasso temporarily becomes the Polygon Lasso tool.

Unfortunately, despite numerous requests, the ability to read users’ minds wasn’t a Version CS upgrade feature. The following sections show you what you have to do to get Photoshop to recognize your wishes.