Re: Viewfinders

[graywolf]

A pentaprism is a 5 sided solid glass prism. A penta mirror is a 5 sided hollow 
equavalent made up of platic mirrors glued together along the edges. Both 
reflect the image multiple times ending up with the image from the reflex mirror 
right side up and right way around. The advantage of the glass prism is it has 
very good light transmission. The advantage of the mirror prism is it is light 
weight, and can be made cheaply if desired.

A well made (expensive) porro prism (another name for a mirror prism) is almost 
as good as a good glass prism (they use them a lot in binoculars). A cheap 
poorly made porro prism is a piece of junk.

--
Joseph Tainter wrote:
"1. Penta Prism (old and/or expensive) vs Penta Mirror (modern and/or
cheap) - construction."
Thanks, Boris. Those were the terms I was looking for.
But what is the difference between prism and mirror viewfinders? Don't 
prism finders use mirrors?

Joe

--
graywolf
http://graywolfphoto.com/graywolf.html