Talk:Pentaprism

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The image shown (Image:Pentaprism.png) on this article is incorrect. A pentaprism is not a pentagonal prism, but a roof prism with 45 degree diagonal faces meeting at a peak at the top of the shape. This is required to reflect the resulting image laterally to unreverse the reversed image produced on the viewscreen by an SLR camera's reflex mirror. The true shape of a pentaprism can be seen on the photo near the bottom of this page: Pentaprism at Konica Minolta - dmmaus 00:45, 9 Mar 2005 (UTC)

A pentaprism is correctly shown in the diagram - it's used in optics, independent of its use in photography. However, the type of pentaprism used in camera viewfinders adds an extra roof section to one of the reflecting sides to give the lateral inversion. It's more properly called a "roof pentaprism" but casual use omits the "roof" part of the name. 128.196.200.115 18:11, 9 Mar 2005 (UTC)
I've added additional information about this to the article. It would be nice if someone could provide an image of the SLR "roofed" version. - dmmaus 05:35, 11 Mar 2005 (UTC)

Contents

[edit] Revert problem

Something has gone wrong when reverting. Appartently I can choose from a version with one contrib or another contrib but not both :-( I'll fix it as ASAP, using the history.

Everything is OK now, I hope. We have got all new stuff, ditched the vandalism and still retained the new interwiki-link. Shinobu 13:55, 8 Apr 2005 (UTC)

[edit] Is the Roof Pentaprism image correct?

I contribute mainly to the french wikipedia. I tried to translate this article to french (actually only the part concerning the roof pentaprism, and including it directly in an article discussing SLRs). The thing is that a user quickly removed it, stating the picture (as well as the text) is wrong.
Since other wikipedia's in the world use this roof prism picture (or a similar one with the same principle) I doubt this (and it seems quite OK to me anyway), but just to know: is there any other sources on the Internet explaining the way a roof pentaprism works, preferably with some sort of illustration? I made some search and found nothing. --Jérémie A. 12:43, 28 February 2006 (UTC)

It's correct, as is easily shown using secondary school level geometry. Shinobu 15:43, 3 March 2006 (UTC)

[edit] the roof

I can easily believe that such a thing works in theory, but what about in practice? That roof edge is right in the middle of the image. It's not going to be perfectly machined. It sure seems that the camera will have a line down the middle. AlbertCahalan 04:26, 9 April 2006 (UTC)

[edit] the image of 2 pentaprisms are incorrect

1) The un-roofed pentaprism that is coated (figure above) will result in an upright and same left-to-right image.

2) The roofed pentaprism (figure below) will result in an upright BUT different left-to-right image —Preceding unsigned comment added by Wibi82 (talk • contribs) 12:08, 6 October 2007 (UTC)

[edit] Light beam crossing

Someone must explain why the crossing of the rays doesn't affect the final image. —Preceding unsigned comment added by 79.114.19.68 (talk) 10:01, 1 May 2008 (UTC)