Jim, roof prisms are used for compactness. They don't offer any optical advantages over Porros and must be made to a tight standard. You usually see them in very high-end binos, and those inexpensive sporting compact binos, such as my Brunton 12x25mm seen in the PSO photos on mt Gallery page. The "roof" term applies to its resemblence to the peak of a houses roof for two of the internal reflections. C. --- Jim Gibson <xajax99@yahoo.com> wrote:

Chuck & Kim I saw your post that mentioned roof prisms. I had never heard the term so I decided to google up some information. There are tons of sites talking about roof prisms and two that I thought might be of interest are included here:

Roof physics http://www.kireinc.com/english/Roof_Prism.htm

Comparison

http://www.birdwatching.com/optics/roof_vs_porro.html

After reading several articles, I am not sure how roofs differ in appearance or construction from the Porro. The roofs look just like the prisms I had in and old pair I once had.

Jim

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