It's generally a given that for the same dollar spent you get better optical quality in a porro over a roof.
The downside seems to be that because of their design, porros are not as durable as roofs especially in holding their collimnation. This is true because roofs focus internally and have a single hinge.
I thought I saw somewhere that manufacturers had found a way to focus porros internally and to have them hold their collimnation with a single hinge.
Would anyone please comment.
I have found that porros offer a transparency of view that all but the best roof prism binos cannot offer. The porro prism system is simpler. One less trip through the reflections of the prism. It also seems true that porros are somewhat more delicate than roofs. And I believe you are right about internal focussing porros being more rugged -- as well as better for waterproofing/fogproofing. Pentax porros have been internal focussing for many years. Minox and Leupold have recently offered internal-focussing binos that are impressive. One drawback to the internal focussing design seems to be a modest field of view compared to conventional porros and the best roofs.
ScoutMan,
Internal focus Porros are nothing new. Kern Focalpin Porros from 30 years ago used an internal focusing lens system just like the one used in many current roof prism bins. Swarovski SL Porros from 20 years ago had completely immobile cemented prism clusters and a single hinge. Neither of these things has anything to do with the prism type.
Among current Porros there are some internal focus models with single hinges sold by Minox, Leupold and Opticron. Pentax Porros have single hinges, not sure about internal focus. The idea that roof prisms hold their collimation better probably comes from the inferior method of collimation used in most cheap Porros now in which set screws are used to adjust the prism shelf. It's more shock resistant to have an fixed shelf and collimate with eccentric objective rings.
Henry