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Pentaprism and pentamirror are used in the viewfinder systems of single-lens reflex cameras.

A pentaprism is a five-sided reflecting prism used to deviate a beam of light by 90°.

pentaprism

Pentamirror is the optical device used in the viewfinder systems of cheaper 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.

pentamirror

Instead of the solid block of glass of the prism in pentaprism system, here 3 simple mirrors are used to perform the same task. This is cheaper and lighter, but generally produces a viewfinder image of lower quality and brightness.

五棱镜和五面镜用在单反相机的取景器上。

五棱镜是五面反射的棱镜，将光束转变90度。

pentaprism

五面镜是用在较便宜的单反相机的取景器上，使成像上下与左右均倒置。

pentamirror

五面镜不是用一整个玻璃棱镜，而是用3块镜子来达到相同的目的。五面镜更便宜更轻，但是成像的质量和亮度差。