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Why no reverse porro from the big three? (1 Viewer)

matt green

Norfolkman gone walkabout
Spent some time glassing for garden birds this afternoon with an old nikon 8x21 reverse porro, unsure exactly which model it is but certainly not current and now looking rather dated with its intergrated fold down rubber eyecups/diopter adjustment..however the optics seemed really quite good and combined with the steady featherweight body it seemed like a very usable little piece of kit.

As far as I'm aware the big three do not, or have ever produced a compact reserve porro prism which seems a shame considering the formats potential to deliver something special with the right glass etc. Not sure about what size objective lens elements can be designed around these little binocs?

Rather like the sound of a high quality take anywhere 7 or 8x24, especialy as some 8x32 are almost the size of smaller bodied 42mm binoculars, surely a reverse porro would smoke a twin bridge roof with the same magnification and objectives?

Matt
 

henry link

Well-known member
The largest reverse Porro I recall was a Bushnell 8x30 Natureview. The design could probably be done with objectives close to 40mm. I would prefer that to the widely spaced objectives In traditional Porros.
 

[email protected]

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I never did care for reverse Porros much. Without the widely spaced objective lenses that the traditional Porros have you don't get the 3D stereoscopic view that I prefer. IMO the wider the objectives the better. The 3D image of a traditional Porro makes the bird "pop" out from the foliage or trees behind it, whereas, in a roof or reverse Porro everything is flat like a pie plate, or it is like you are looking at a picture with a flat surface. Reverse Porros have even less 3D than roofs because their objectives are so close together. The parallax between right and left images which can cause problems at less than about 30 feet with field merging in widely space objectives does not bother me at all.
 
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matt green

Norfolkman gone walkabout
I never did care for reverse Porros much. Without the widely spaced objective lenses that the traditional Porros have you don't get the 3D stereoscopic view that I prefer. IMO the wider the objectives the better. The 3D image of a traditional Porro makes the bird "pop" out from the foliage or trees behind it, whereas, in a roof or reverse Porro everything is flat like a pie plate, or it is like you are looking at a picture with a flat surface. Reverse Porros have even less 3D than roofs because their objectives are so close together. The parallax between right and left images which can cause problems at less than about 30 feet with field merging in widely space objectives does not bother me at all.
Yes, having read recent comments on the 3d aspect of porros I can see how this would detract from the image..I guess the objectives could be spread out further apart but would no longer appeal to those wanting a pocket binocular!

We need the habicht to have a dirty weekend with the nl pure, the resulting offspring would be pretty interesting..kinda like a traditional porro but all weather sealed and wrapped up in rubber with a nice big focus wheel and intergrated diopter, maybe push the objective size to 44mm for a little more light gathering,

...as far as reverse porro 8x21 I have now well and truly strayed off track!

Matt
 

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Well-known member
Supporter
Yes, having read recent comments on the 3d aspect of porros I can see how this would detract from the image..I guess the objectives could be spread out further apart but would no longer appeal to those wanting a pocket binocular!

We need the habicht to have a dirty weekend with the nl pure, the resulting offspring would be pretty interesting..kinda like a traditional porro but all weather sealed and wrapped up in rubber with a nice big focus wheel and intergrated diopter, maybe push the objective size to 44mm for a little more light gathering,

...as far as reverse porro 8x21 I have now well and truly strayed off track!

Matt
What is interesting, and I never realized it till I bought the big Porros like the Fujinon is not only does wide objective spacing give you more 3D but the wider spacing the better the 3D. The 3D stereoscopic view is proportional to the width of the spacing. The Habicht 10x40 GA has good 3D but the bigger Fujinon FMTR-SX 10x50 is even better and the Fujinon FMTR-SX 7x50 is a little better than the 10x50 because it has better DOF so combined with the exceptional 3D and excellent DOF the view through the Fujinon FMTR-SX 7x50 is amazing.
 
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jring

Well-known member
Hi,

while reverse porros are good options for inexpensive pocket bins and actually make a lot of sense for very close range viewing as in the Pentax Papilio, I'm not sure if I would like a reverse porro from the teutonic trinity. At least Zeiss and Swaro have shown that they can build competitive 8x25 roofs at what I think is the minimum pricepoint they are willing trade on...

Also unlike normal porros, we don't get the nice 3d effect with reverse porros (actually even less than in a roof due to the decreased stereo base). Also there is the illusion that close objects appear to be smaller than in roofs due to the increased stereo base in normal porros - has anybody tried if that is reversed in reverse porros with their smaller stereo base too (might actually be an advantage)...

Joachim
 

Alexis Powell

Natural history enthusiast
United States
The largest reverse Porro I recall was a Bushnell 8x30 Natureview. The design could probably be done with objectives close to 40mm. I would prefer that to the widely spaced objectives In traditional Porros.

Also worth remembering, though not technically a reverse-porro, was the underslung-porro Bausch & Lomb 8x50 Elite.

--AP
 

henry link

Well-known member
I forgot about the 8x50 Elite. I would have bought that one just for the narrow objective spacing, but I thought the FOV was too small. I recall seeing a few other inexpensive over/under Porros back in the 90s (masquerading as roofs, I think) and of course there was the Rollei 7x42, which I would have bought except for the lack of a focuser.
 
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henry link

Well-known member
Also there is the illusion that close objects appear to be smaller than in roofs due to the increased stereo base in normal porros - has anybody tried if that is reversed in reverse porros with their smaller stereo base too (might actually be an advantage)...

Joachim
Yep, the effect is reversed. Close objects appear larger in reverse Porros than through inline roofs of the same magnification.
 

jring

Well-known member
Yep, the effect is reversed. Close objects appear larger in reverse Porros than through inline roofs of the same magnification.

Thank you Henry, I guess I'll have to try with my Papilio 6.5x and my Trinovid 7x42 (closest match of reverse porro and roof)...

Joachim
 

Binastro

Well-known member
Kite 12x42 and 16x42 APC may be reverse Porroprism?

From memory the Minolta Activa 12x50 may be up down stepped.
There are several others.

Regards,
B.
 

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Kite 12x42 and 16x42 APC may be reverse Porroprism?

From memory the Minolta Activa 12x50 may be up down stepped.
There are several others.

Regards,
B.
I am pretty sure those two Kites are reverse Porros. Usually you can tell if it is a reverse Porro because the objectives are close like a Papilio.
 

[email protected]

Well-known member
Supporter
In Fujinon's literature it says the new Fujinon TSX 14x40 has Reverse Porro prisms but the older model TS 14x40 has a roof prism. It seemed weird that they would totally change the prism in an update of the binocular, so I asked them about it. They said both binoculars have a Porro prism in the eyepiece AND a roof prism in the body of the binocular. I found that weird but at least it explains the specifications.
 

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