Pentamirror

A pentamirror is an optical device used in the viewfinder systems of various single-lens reflex cameras instead of the pentaprism.

[1] Instead of the solid block of glass of the prism in pentaprism system, here 3 mirrors are used to perform the same task.

This is cheaper and lighter, but generally produces a viewfinder image of lower quality and brightness.

[2] This optical device is often (more precisely) referred to as roof pentamirror because of the roof-like ridge.

This optics-related article is a stub.