http://www.liujianfei.com/blog/archives/52
单反相机中的五棱镜与五面镜
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.
pentaprism
pentamirror
Canon
xD xxD
xxxD xxxxD
Nikon
D70 and upper
D60 and lower, D5000
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。
五棱镜
五面镜
Canon
xD xxD
xxxD xxxxD
Nikon
D70 及更高
D60 及以下, D5000
