A pentamirror is an optical device used in the viewfinder systems of various single-lens reflex cameras instead of the pentaprism. It is used to reverse again the upside-down and laterally reversed image coming from the reflex mirror.
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.
This optical device is often (more precisely) referred to as roof pentamirror because of the roof-like ridge.
- Mike Stensvold. The Complete Idiot's Guide to Photography Like a Pro, 2002, page 26.
- David D. Busch. Digital Photography All-in-One Desk Reference for Dummies, 2006, page 106.
- Paul R. Yoder. Opto-Mechanical Systems Design, 2005, page 435.
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