Focussing screen

Enhanced focussing screens
Compiled by Q.-Tuan Luong for largeformatphotography.info ...

If your camera has interchangeable focussing screens and if you find yourself doing a lot of manual focus work you might want to consider investing in a screen that can provide you with useful manual-focus feedback.

split-prism - a focus aid that may be built into a focussing screen, giving a split image which joins together when in focus.
Sports finder - a folding frame viewfinder.
spot meter ...

See also: Autofocus, Element, Viewfinder, Sensor, Film speed