When I crop a photo in Lightroom, I often can’t judge whether I like it or not with the whole photo still showing, so I used to have to get out of the crop, decide, then go back in if I want to adjust it further.

Here’s a tip I picked up from Victoria Bampton (aka the Lightroom Queen) quite a while back:

• Open the crop tool, and set your proportions, if needed.
• Turn on Lights Out mode, with the shortcut L. Typing L once will dim the background; typing it again will black out the background.  Drag on the crop edges or corners to make your crop. In Lights Out mode, you will not see what is outside the boundaries of the crop.

• When you are happy with it, type L a third time to restore the background.
• As usual, put the crop tool away by clicking back on it or hitting Enter/Return.

Enjoy!