I have looked around and would like to know what is the difference, and advantages of both types of bino against the other?
Is it true, (generally speaking) that porros are not waterproofed whereas roofs are (not all of them of course).
Does it matter if you wear specs or not? - I must admit, I've only got or owned porros, but whenever I've used roofs they've impressed me - is there any great difference, or as usual, down to personal preference.
In my experience, a lot of both bins are seen, but I'd say most "casual" observers use porros, and most serious birders have roofs - this is not exclusive, but generally speaking.
Steve
porros tend to have a larger field of view. They are easier to manufacture due to the style of design. They tend to be at least as good optically dollar for dollar. They are however more bulky, less durable, and usually not waterproof. Top of the line roof binoculars like those manufactured by Swarovski and Leica are considered by many to be the best all around birding binoculars. Many still swear by the old-fashioned porros saying that they are better optical performers than roofs even though they may not be as comfortable to handle due to their design.
If optical quality were the only criterion most binoculars would still use porroprisms. The optically best possible roof prism (the phase-corrected Abbe-Koenig type used in the 42mm Zeiss FL) only approximately equals the performance of a porroprism at greater cost. The Schmidt-Pechan roof prism used in all other current binoculars will always produce a slightly dimmer image because it requires more reflections and mirror coating. In addition roof prisms require phase correction coatings. Without those the image is quite noticeably degraded as to sharpness and contrast compared to porro.
The above applies only to the prisms, which are only part of the total optics in binoculars. So an expensive roof prism binocular with a sophisticated eyepiece and objective design and the best possible coatings can certainly be optically superior to a porro with a simple objective and eyepiece even though the roof prism, taken alone, is actually slightly optically inferior to the porro.
Porros could use exactly the same internal focusing elements as roofs (or a moving objective combined with a cover glass as in the new Canon 10X42 L porro) and be just as waterproof. Eye relief is completely unrelated to the prism design.