Narrative's full-screen mode lets you focus completely on a single image, giving you a distraction-free way to evaluate your shots without leaving your culling flow.
How to use full-screen
Press F on your keyboard to toggle fullscreen on or off at any time while culling.
Once in full-screen, everything works exactly as you'd expect:
Rate images using your number keys as normal
Navigate between images using the arrow keys
Press F or the ESC key to exit full-screen and return to your standard view
That's it, no interruption to your workflow, just more screen to work with.