Method 5 at this link (http://m.wikihow.com/Take-a-Screenshot-in-Mac-OS-X) is EXACTLY what I’ve been looking for.
When I sharpen photos in Adobe Bridge, I press/hold the option key (Mac) while clicking the masking slider to see the areas being affected. Often, that black and white preview is so cool to look at, so I’m glad there’s a screenshot option that includes a timer.
It’s the only way to get a screenshot of this adjustment screen because the keys to make the adjustment are some of the same ones needed to take a screenshot.
Here’s the regular photo and what the above sharpening adjustment looked like at one point in the process.
I may make a whole series of these!