Porro v Roof - which & why? (1 Viewer)

[Quacker]

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

 

[lvn600]

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.

 

[henry link]

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.

 

[Leif]

Steve: As Henry suggests, at a given price a porro will tend to give better optical quality simply because roof prism binoculars cost more to make for the reasons given. They also tend to have a more 3D feel to the image due to the greater separation between the objective, but focus less close for the same reason. Porro prism bins tend to be larger and hence less comfortable to hold. I have also noticed that the focus on porro prism bins tends to be stiffer and they are harder to waterproof. This is because the eyepieces must slide back and forth on tubes, but the gap between the eyepieces and the supporting tubes must be small to allow water proofing, and large to allow an easy free focus i.e. you can't have both. (Actually you could focus a porro prism instrument and make it easier to waterproof by moving the objectives to focus and adding a watertight glass window in front of each objective. But the manufactuers have not chosen this approach, presumably because it would make the instrument expensive, and it would still be bulky and probably would not sell.) Someone (Henry?) once pointed out that on many porro prism bins the two eyepieces flex slightly (my Nikon Egret 8x40 does this) which does not help matters. Lastly, as Henry suggests, there are not many good porros made today as manufacturers tend to put their latest wizzy technology on roof prism bins. They seem to regard porro prism bins as something for beginners, though I guess the blame for that lies with us customers since money talks.

On several occasions I borrowed a friend's Optolyth 10x50 porro prism bin which in many respects was a rather nice glass, knocking for six a similarly priced roof prism instrument, but it had little eyerelief, a small fiddly focus wheel, and was not waterproof.

Leif

 

[Leif]

Henry: I've just noticed that you have already mentioned that a porro prism bin could be focussed by moving the objectives, with cover glasses to gain waterproofing. Do you know if this is this new to Canon or have other manufacturers done this before? (I'm referring to porro prisms bins of course, since Zeiss and Swarovski have done this with roof prism bins.)

Leif

 

[mcdowella]

I'm not completely sure, but the statement " The Pentax-developed inner-focus optical design contributes to the reduced size and weight of these models, despite the large aperture of their objective lenses. At the same time, it improves the image sharpness and reduces distortion to a minimum." at http://www.pentaxuser.co.uk/pages/news/nws_PCFbinoc.htm suggests to me that Pentax may make a porro with internal focus. All the same, if you ignore the problems of waterproofing, the traditional moving-eyepiece porro focusing appears to be mechanically and optically simpler.

 

[Swedpat]

For me it depends on purpose and situation. They have both of them advantages and disadvantages. A porroprism bino gives better optical performance for the price, but a roof bino is mostly more durable. One disadvantage with a roof bino is the starfilter effect which comes up when looking at strong light sources. This effect isn't in the most cases visible or a big problem, however. But I guess this effect is the reason it's very uncommon with roof prism boating binoculars. When looking at dark sea against lighthouses and other light sources this effect likely isn't desirable. Maybe someone here can confirm my theory?

 

[Wehr]

Most of the modern designs are roofs. Roof prisms are much more expensive than porro prisms. Therefore roof bins are expensive. Making modern porros as stabil, waterproof, gas filled and with internal focussing as top roofs would render the porros perhaps even more expensive than roofs. But there are no such modern porros available, because people want to have roofs. Optical quality can be made the same, no technical reasons for differences. Porros' objectives can be bigger in diameter and porros provide a bit more 3D on short distances.

 

[henry link]

Henry: I've just noticed that you have already mentioned that a porro prism bin could be focussed by moving the objectives, with cover glasses to gain waterproofing. Do you know if this is this new to Canon or have other manufacturers done this before? (I'm referring to porro prisms bins of course, since Zeiss and Swarovski have done this with roof prism bins.)

Leif

Leif,

I'm guessing that at least some WP reverse porros use moving objectives with cover plates. Its hard to tell from the Pentax press release Mr. Mcdowell refered to whether their "inner-focus" means focusing element, moving objective or perhaps moving prism. The only traditional porro I know about that used a focusing element was an old Kern 7X50, highly prized now by collectors.

Henry

 

[chartwell99]

Leif,

I'm guessing that at least some WP reverse porros use moving objectives with cover plates. Its hard to tell from the Pentax press release Mr. Mcdowell refered to whether their "inner-focus" means focusing element, moving objective or perhaps moving prism. The only traditional porro I know about that used a focusing element was an old Kern 7X50, highly prized now by collectors.

Henry

The Nikon reverse porros from the mid-1970's used moving objectives with cover plates. I owned an 8 x 24 at the time and thought the approach had promise. Interestingly, Nikon used moving objectives and protective cover plates for its high end roof, the 8 x 40 Classic Eagle as well. My guess for the lack of popularity of the approach over the years is light loss issues resulting from the additional optical surface.

 

[Quacker]

Thanks for the replies - I am considering both Nikon 8x32 SE Porros and 8x32 HG's - both quality bins, both with their own followers and because of the lack of waterproofing, the SE's (though regarded by some as the finest optics available) seem to be second choice.

Having read all about these in the Nikon bins section, I'm now a little further forward.

Regards

Steve