'RetroPorro' a Possibility says Leica (4 Viewers)

[John A Roberts]

Hi JA,

There are two related concepts in relation to the light path in prismatic binoculars:
A) Axial Offset (Is the light path on the same axis before and after having passed through the prisms?), and;

B) Axial Orientation (If there is offset, how are the objective axes - and therefore the objectives - orientated in relation to the eyepieces of the binoculars?).

Most roof prisms have no offset. With Abbe-Koenig prisms there may be either no offset or a slight offset, depending on the designer’s preference
(the latter is useful with larger diameter objectives as it allows the eye pieces to still have a sufficiently narrow minimum IPD)

With Porro Type I and Type II prisms and with Perger prisms, there is always offset. However, the amount of offset varies with the particular prism design *


Offset is orientated in one of four ways, depending on the preference of the designer:
- objectives outside of eye pieces (the traditional Porro prism binocular choice to maximise 3D effect . . . )

- eye pieces outside of objectives (the classic inboard Porro configuration, to maximise compactness in smaller binoculars)

- eye pieces above objectives (including the Leica Perger prism Geovids, the Canon Porro Type II prism IS models, and the British Avimo Porro Type I prism binoculars . . .), and

- objectives above eye pieces (including the Bausch & Lomb Elite 8x50’s with Porro Type I prisms) . . .

* As Holger indicates, with non-roof prism binoculars: Porro Type I prisms have the most offset; Porro Type II prisms have less, and; Perger prisms as used in the Geovids have the least.


For examples of the offset and orientation mentioned in the above binoculars, see the images in posts #4 and 10 at: High end porro's


John

 

[jafritten]

Hi JA,

There are two related concepts in relation to the light path in prismatic binoculars:
A) Axial Offset (Is the light path on the same axis before and after having passed through the prisms?), and;

B) Axial Orientation (If there is offset, how are the objective axes - and therefore the objectives - orientated in relation to the eyepieces of the binoculars?).



* As Holger indicates, with non-roof prism binoculars: Porro Type I prisms have the most offset; Porro Type II prisms have less, and; Perger prisms as used in the Geovids have the least.


For examples of the offset and orientation mentioned in the above binoculars, see the images in posts #4 and 10 at: High end porro's


John

Thank you very much for your clarifying the matter, John. The images in the High end porro thread are very illustrative. My idea of a porro would be one with objectives outside the eye pieces.

 

[Holger Merlitz]

Thank you, Holger. One thing that I (and probably many other people) like about porro designs is that they have a wider stereo basis than roofs and thus generate a better representation of depth of space (3D view), on the downside they are "bulkier", naturally. So, you can't have one without the other, right? Maybe I don't understand the term "axis-offset" correctly.

Right, you can´t have one without the other. To obtain a wildly exaggerated 3D view, people have designed these "tele-stereoscopes" with huge objective separations. Through such a device, objects around us are looking like toys.

Cheers,
Holger

 

[jafritten]

Right, you can´t have one without the other. To obtain a wildly exaggerated 3D view, people have designed these "tele-stereoscopes" with huge objective separations. Through such a device, objects around us are looking like toys.

Cheers,
Holger



View attachment 1416624

That's a bit over the top... It must be some 30 cm in width. Certainly not of much use for birding. Maybe to simulate drug abuse. Thanks for the image.

 

[Canip]

RetroPorro a possibility says Leica?
Sorry I am a bit late to the party, but in fact, a Leica Porro is still a reality (at least until quite recently,) see pic (armoured army version with laser filter).

At least for 8x30, they still have the design, the tools and access to the materials, even a finished and tested center focus version is part of what they took over from Kern.

So they could start right away making something nice with RFOV <8 degrees, central focus,

 

[John A Roberts]

And four more images of the much rarer CF Leica/ Kern, from Frank on Flickr:

https://flic.kr/p/2jsGE2R

John

 

[Gijs van Ginkel]

And if You want to see different Kerns and a Kern Leica tested, see the most recent test of 8x30/32 bioculars on the WEB-site of House of Outdoor in which I have investigated also the 32 mm Swarovski NL , Zeiss Vicory SF and GPO.
Gijs van Ginkel

 

[John A Roberts]

For some more information about the CF Leica/ Kern that was officially known as the 'Pizar Elit', see at: Kern 8x30 Pizar Elit - Center Focus Rarity

Also see the information from a 4 page flyer for the IF military version, which includes the optical construction (the flyer seems to date from October 1984).
It mentions the CF model '. . . which also conforms to the most stringent military requirements' (see the bottom of page 4).


John

 

[simple]

I've often thought - It would be great if they brought back the old build Trinovid (BA/BN) - I know it is a roof prism but...

Fantastic hardcore build, well balanced, probably the best eye cups in the business (IMO) and could actually stand-up to hardcore use (unlike most of the newer binoculars in my experience). Now put modern optics in that old style build (the new one is nowhere near as good! nor is it optically) and I think you'd have a Birders favourite again!