Leif and Ed,
Thanks for the response Now I really do not want to sound foolish, but a question remains here.
My educational background is a graduate Degree in Zoology, specifically Mammalogy. The field of Ethology was a strong secondary interest. When dealing with Mammalian behavior (or any form of Animal Behavior) a critical facet to understand is how your study subjects see their world. So I really do think I have a pretty good handle on stereopsis.
The only way any of this makes sense is to come to the conclusion that even though the beam of light from wide spaced objectives is moved to pass through the narrower space provided by the eye, is that somehow the 3-D aspect remains. Even though (of 4 total) there are two 90* passes which physically move the beam toward center of the ocular. Obviously the eyes can't be widened out to match the objective spacing. The fact that stereo effect is not lost in those moves is where I have a hard time with the perceptual handle. I assumed that one focused beam of light from a roof was the same as the same focused beam of light from a porro. Evidently not.
Ed, I am sure that two slightly different viewpoints provide a more 3D answer. |=)|
Steve,
This is a very good question. I did quite a good job of "confuddling" :h?: the issue for myself, as I was having the same conceptual difficulty, and it has taken me quite a while to wrap my head around it.
Not until I read Leif's comment did the penny finally drop ..... :t:
"The 3-D aspect" for a PorroI does remain effectively (through all the prism contortions), since, from each side:-
the original view (toward the viewed object) is from the perspective of the objective lens and it's corresponding additional offset from the exit pupil offset (from the centreline).
Think of the view from the objective lens toward the viewed object as "the input". The "input" is the visual information (the view) that comes out exactly the same (ok, except for magnification, abberations, distortions, etc) at the "output" (the exit pupil).
The fact that you have two "inputs" (one from each objective lens) delivered to two "outputs" (exit pupils - hopefully in-line with your eyes - barring facial asymmetry, and all the other clarence the cross-eyed lion antics of setting that for different distances), goes to make up the viewed image (magnification notwithstanding). So the objective spacing relative to your IPD does matter.
I'm sure that would've been easier with pictures, but at least now I think I get it?!! :hi:
I have no comment to make about magnification, other than I'm damn glad it helps me see better!
I also prefer a 70° Afov over a 60°, or 50° one. I don't have a frame of reference for anything wider in binocular world save from memory which has now vanished!
Chosun :gh:
Steve,
You may have already had your "Eureka" moment about this, but I think it might be be easier to grasp if simplified to one eye. The off-set of a single barrel of a Porro binocular acts just like a horizontal periscope, albeit a very short one. Obviously a periscope only works because the eye sees the world from the POV of the periscope's entrance, not it's exit.
Henry
I do see how folks may find those dogleg "half a porro binocular" monoculars ugly. As for the Carl Zeiss Jena "Turdmon" 8x21, well that looks like a dog's digested dinner. The Docter version looks OK though.Lee,
that's a good and interesting point. The question is why do Zeiss (and most other manufactorers) only use S-P prisms with their range of monoculars? With monoculars the ascendancy of the S-P prism over the porro is still even greater than with binoculars.
Steve
I do see how folks may find those dogleg "half a porro binocular" monoculars ugly. As for the Carl Zeiss Jena "Turdmon" 8x21, well that looks like a dog's digested dinner. The Docter version looks OK though.
Ed, I am sure that two slightly different viewpoints provide a more 3D answer. |=)|
As you know Steve, this forum has a very long and proud tradition of doing the utmost to dissuade anyone making enquiries about monoculars from going out and actually purchasing one || The arguments against always given are regarding the ergonomics. No question I have been affected by that.Norm, if you have to choose a monocular for occasional birdwatching and the optical quality is the same, would you prefer the porro or the roof version?
Steve
I have a 1989 set off Bausch & lomb Discoverers in 7x50 .They are the only set of bins I have ever owned.They seem very nice. I am thinking of going to a set of high quality roofs to get away from the heavy 7x50 B&LD. and a set of water proofs. I want to stay at 7 or 6 power because at 61 it is getting hard to keep them steady.
I think I will change my answer from "porro" to "I can't choose between porro and roof".
The last weeks I have used my Nikon 8x32 SE. I would choose the SE for it's sharpness, the 3D and the natural view. But yesterday I was birding with my Nikon EDG 8x42..and it is a very nice binocular. Very good focus, easy to use, you dont get so cold in freezing temperatures when holding it, bright, accurate colors, water resistant etc. It is privileged to have the opportunity to choose between two such fine binoculars!
But..if I really had to choose between the SE and the EDG..maybe I would choose the EDG after all. It may not be as sharp as the SE and the view is not as natural either. But it has so many strong features and basically not one real weakness, making it by far the best all round binoculars of the two. So..if someone had pointed a gun to my head I think I had picked the Nikon EDG 8x42 roof after all. Problably..
And if I would regret that choice, I can always sell the EDG and buy two new Nikon SE instead.. :-D
The optics on the 7x50 B&L Dis.are great and no shake from them. They are to heavy any more.
....... The only inexpensive 7 x 42 roof prism that I know of is Leupold's Hawthorne. Check their specs on the Eagle Optic's website........
Bob
All things being equal, optics, build, weather protection, what would your preference be?
And a brief description why?