Pentamirror

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 laterally reversed image coming from the reflex mirror.^[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.^[3]

Notes

^ 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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[1] Mike Stensvold. The Complete Idiot's Guide to Photography Like a Pro, 2002, page 26.

[2] David D. Busch. Digital Photography All-in-One Desk Reference for Dummies, 2006, page 106.

[3] Paul R. Yoder. Opto-Mechanical Systems Design, 2005, page 435.

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