Since Lightroom is all about photos and most people like to see their photos larger on screen, I wanted to give you some of the shortcuts and secret handshakes to help make that happen
1. Just press the F key (for Full Screen) – This is definitely the simplest. Where ever you are in Lightroom, just press F for Fullscreen and Lightroom will show the photo full screen with all of the interface hidden.
2. If you want to zoom in to 100% (or some other amount), just go to the Navigator panel in the Library or Develop module. Then click the Fill, 1:1, or custom zoom option at the top left. Oh and while you’re at it, if you don’t want to click the options in that Navigator panel, you can use the keyboard shortcuts Cmd +/- (plus or minus) which would be Ctrl +/- on a PC.

3. If you’re in the Library module and you’re in Grid view, you can just press the Spacebar key to go 1-up on the photo you have selected. It’s not full screen view, because it still keeps the interface available. But it’s just a single photo view.