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Prisms! S-P, Uppendahl, Abbe-Koenig..

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Old Friday 14th February 2020, 19:33   #26
wdc
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So, where is that product? Is the world waiting for it? (or just a handful of binogeeks?)
Its as if the last step in this evolution is to go back to square one, and modernize what worked so well in the first place. After that: game over!

Or, we just lounge around Omid's New Horizons cafe and wait for some news...

-Bill

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Old Friday 14th February 2020, 22:18   #27
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Or, we just lounge around Omid's New Horizons cafe and wait for some news...

-Bill
Why just seat around and wait for me? You -and others- can actually participate in the innovation process.

I assure you that established companies such as Zeiss, Swarovski, Nikon, Leica, etc. are going to continue the exact same trajectory that they have followed in the past 30 years. If you simply lounge around and wait for "someone else" to innovate, we'll get -at best- what you predicted: go back to square one, and modernize what worked so well in the first place. The worst case scenario is that these companies will simply stop making binoculars and focus on more lucrative product sectors.

A significant innovation in binoculars, if possible, will likely come from sources outside major optical companies. Here is an example topic to think about: Why do we need to focus our binoculars? Seriously, why is focusing necessary?! Think about this question and write your answer in New Horizons please.

Happy Friday
-Omid

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Old Friday 14th February 2020, 22:32   #28
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Actually, a well-made porro doesn't need ED glass. The problems with CA only reared their ugly head when the manufacturers introduced focusing lenses behind the objective lenses.

Hermann
I know porros didn't suffer as much as those roofs with internal focusing, but the performance of ED porros, such as the ED version of the Swift Audubon, as well as some models from Celestron, were impressive.

--AP
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Old Saturday 15th February 2020, 00:23   #29
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Originally Posted by Omid View Post
Why just seat around and wait for me? You -and others- can actually participate in the innovation process.

I assure you that established companies such as Zeiss, Swarovski, Nikon, Leica, etc. are going to continue the exact same trajectory that they have followed in the past 30 years. If you simply lounge around and wait for "someone else" to innovate, we'll get -at best- what you predicted: go back to square one, and modernize what worked so well in the first place. The worst case scenario is that these companies will simply stop making binoculars and focus on more lucrative product sectors.

A significant innovation in binoculars, if possible, will likely come from sources outside major optical companies. Here is an example topic to think about: Why do we need to focus our binoculars? Seriously, why is focusing necessary?! Think about this question and write your answer in New Horizons please.

Happy Friday
-Omid
All good points, and appreciate your thinking, Omid. I would still like to see a little bit of revisiting the past and improving upon it, if only for selfish reasons: I'd like a state of the art Porro that fits me! (and has the inherent capacity to outperform the roofs)

As to your question about focus, I'm hoping that will elicit a response from Bill Cook. That may rouse him from his torpor.... But I will think about it as well.

Have a good weekend.

-Bill
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Old Saturday 15th February 2020, 15:41   #30
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The photo below is posted with permission of Cory Suddarth of Suddarth Optical.

According to Cory:
"They are not all from equivalent apertures. The left is the Schmidt-Pecan from a compact. Middle is an Uppendahl used in all Leitz Trinovids, and the big Abbe-Konig On the right is from a Made in Japan, 9x63 roof prism model. "


It would be pretty obvious why manufacturers would gravitate towards the S-P IF the prisms were all meant for the same aperture.

-Bill
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Old Sunday 16th February 2020, 01:33   #31
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Quote:
Originally Posted by wdc View Post
The photo below is posted with permission of Cory Suddarth of Suddarth Optical.

According to Cory:
"They are not all from equivalent apertures. The left is the Schmidt-Pecan from a compact. Middle is an Uppendahl used in all Leitz Trinovids, and the big Abbe-Konig On the right is from a Made in Japan, 9x63 roof prism model. "


It would be pretty obvious why manufacturers would gravitate towards the S-P IF the prisms were all meant for the same aperture.

-Bill
Bill, this is getting where I'd like to see this thread go.
We should also consider all prism types including Porro II, Perger etc.

There are only a few major factors to consider, with:-
Size/weight/packaging-offsets, and,
Transmission/micro-contrast/colour rendition
being among the main ones.

I think it would be most useful to describe the volume of each of the prism types in terms of an entrance circle to the prism of aperture diameter dimension 'A'.

That way everything is represented by a formula with reference to 'A' and we can have an apples to apples comparison between the different prism types. By multiplying the resultant volumes by glass density for each prism component it gives us the weight for each prism type - by assigning a millimetre figure to the aperture dimension we get actual weights in grams.

There will be some subtleties which determine the precise aperture diameter required, such as power of the lenses in the objective/focusing group (internally pre-prism focused) , the focal ratio of the binocular , and any effects on that due to physical length of the packaging etc, but largely this will have minor effect on 'A' and may be able to be dealt with via a %factor in practice (bearing in mind this affects Fov which for the purpose of discussion we should try and standardize as much as possible).

It also allows us to define offsets, and physical packaging dimensions also as a multiple of the common parameter 'A' for each prism type.

In the big Zeiss SF thread I know we briefly discussed this for some prism types, with Holger chiming in with some calculations, but it would be very interesting to encompass every type of prism in a standardized way.

Similarly for the other transmission factors etc. I'm on the record as saying that I find 100% internally reflecting prisms to offer the desireable though somewhat esoteric quality of 'clarity'. This will be subtle differences in transmission at various wavelengths, and the effects of lost light on micro-contrast and glare, etc. I know that we are well into the realm of stacking BB's, but hey, I see tree spirits, and other etheric energy at times, have been known to leave my body to fly around up in the sky, and even though my eyes are the same colour they each have their own colour cast particularly around afternoon light into dusk. I readily see CA too - so pardon me if I march to a different beat !

Even though the best 70+ layer dielectric mirror coatings may lose ~1~2 odd % transmission, given that light losses through glass at different wavelengths occurs at different amounts, it may also offer the additional potential for 'retuning' these losses somewhat to offer a flatter transmission curve. I'd like to see some data on that if we can access it (highly doubt it - lol:).

This would provide a better framework for analysis than 50 million people going around in circles with one 'I reckon' in response to another.





Chosun

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Old Sunday 16th February 2020, 01:40   #32
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Just why are prisms even needed in the binocular today?
Modern lenses are plenty good enough to provide a full range of magnification without the extra path length the prisms provide, if camera lenses are any indication.
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Old Sunday 16th February 2020, 01:53   #33
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Originally Posted by Hermann View Post
Depends on how you define "significantly" ...
Indeed. Is the difference in micro-contrast between a well-executed Schmidt-Pechan design and an Uppendahl likely to be discernible only by nitnoids/BB-stackers like our friend denco, or is it likely to be apparent to the average binocular user?

If Leica could make available a Retrovid with the 20% of Uppendahl prisms that passed QC for comparison with the current version, it would be most interesting to have our esteemed contingent look through them - preferably not knowing which was which...

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One other interesting observation we made was this: After we'd done our comparisons I got my old Zeiss West 10x50 Porros (~ 1963) from the car. My friends had got bored with testing optics by that time, so we only did a quick comparison with the new Zeiss 10x40B's, and the results were pretty amazing. Sure, the 10x40's had better contrast and a brighter image, after all, the old 10x50's only have a simple single-layer coating, but the resolution of the old 10x50's was quite noticeably *better*. In fact, the difference was so pronounced that we couldn't help but wonder why Zeiss doesn't make these binoculars with a modern T*-coating anymore. I'm sure they'd beat most (if not all) roof prisms hand down."
I found the above comments really interesting as I had the pleasure of doing a similar comparison - between those same two models - last year. It was a fine autumn day and my main target was the BT Tower, a well-known London landmark about 1km away; lots of little details to compare and contrast betwen the two. Having these two classic models of different eras and designs side by side for some 20 minutes or so was a really enjoyable experience, and I wish I had noted down my impressions in detail. I found the Oberkochen porro comparable in brightness (x50 objectives vs x40 making up for T vs T* coatings, I suppose). Colour rendition at that distance, somewhat to my surprise, was very similar - I had expected the older pair to show more subdued colours at distance (as my 8x30 non-B porro did when compared against the 8x30 SLC mark II I used to own). Resolution, I thought, was very similar between the two, although I need to note that I was wearing glasses (my left eye has slight astigmatism) while using the Dialyt and using the Zeiss West porro straight to my eyes. I really enjoyed both the excellent field of view and the immersive experience of using these old short eye relief porros - the surroundings being blacked out by the eyecups so you feel like you are in a cinema. But being able to observe with glasses on was unquestionably more convenient.

My strongest impression after comparing the two was how the 10x50, despite being around 30 years older, was so close, image-wise, to the 10x40 - a real testament to the intrinsic soundness of the porro design and Zeiss West's ability to build a really good 10x50. The 10x40, however, delivers the same image (to me) in a much handier and more convenient package that gets used quite a bit more. I admire the 10x50 a great deal, but if I had to choose between the two, would keep the 10x40.

I agree that a multi-coated version of the 10x50 would be superb - but whether it would "hands down" beat the very best of today's 10x50 roofs...

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I do, however, believe a well-made porro will have optical advantages over any roof. And these differences will be visible.
If I could ask what advantages these are, and how they would become visible - I would be very much obliged.
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Old Sunday 16th February 2020, 03:04   #34
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Just why are prisms even needed in the binocular today?
Modern lenses are plenty good enough to provide a full range of magnification without the extra path length the prisms provide, if camera lenses are any indication.
A simple answer might be to make the image erect, and right reading.

No prism and it will be upside down. With a mirror diagonal it will be upright, but flopped. Telescope finders use an amici prism to erect the image properly, as far as I can recall.

-Bill
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Old Sunday 16th February 2020, 11:35   #35
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Bill, try this on for size. The posts around this one contain volume formulas for S-P, A-K, Porro, and Perger, prisms. (referenced in terms of 'w' for the 'A' that I suggested).
https://www.birdforum.net/showthread...89#post3059689




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Old Sunday 16th February 2020, 17:00   #36
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I'm on the record as saying that I find 100% internally reflecting prisms to offer the desireable though somewhat esoteric quality of 'clarity'. This will be subtle differences in transmission at various wavelengths, and the effects of lost light on micro-contrast and glare, etc.
I'll second that. But I have to admit I'm not very interested in details of the relative volumes of prisms etc, because that boils down to asking how much effort TIR prisms are worth. My only question is, if a bino is large enough to accommodate them, why hasn't it got them? Then we can just quibble about where the line of "large enough" is. Clearly 50/60mm aperture is large enough; 40 probably is too if you're willing to have it modestly longer, as I would be; 30, not so much.
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Old Sunday 16th February 2020, 19:28   #37
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A simple answer might be to make the image erect, and right reading.

No prism and it will be upside down. With a mirror diagonal it will be upright, but flopped. Telescope finders use an amici prism to erect the image properly, as far as I can recall.

-Bill
So how do rifle scopes and cameras manage this issue?
Is it not simply a matter of adding an extra lens?
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Old Sunday 16th February 2020, 20:08   #38
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Well ... if you disregard the roofs for a moment and just look at optical performance, I'd argue there hasn't been all that much progress in the past 70+ years. Some of the old porros could easily compete with today's crop of alphas - if they had modern multicoatings.

Hermann
Hi Hermann,

You are correct of course. I was being polite and gentle with my statement. However, this long period of "non-progress" should not disappoint us from searching for improvements in binoculars. Consider the archery bow. It was invented by our ancient ancestors more than 10,000 years ago (historical records in Europe go back to 18,000 years ago.) The bow's basic design was virtually unchanged until 1966. Then a significant invention occurred: the compound bow.



-Omid

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Old Sunday 16th February 2020, 21:37   #39
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I'll second that. But I have to admit I'm not very interested in details of the relative volumes of prisms etc, because that boils down to asking how much effort TIR prisms are worth. My only question is, if a bino is large enough to accommodate them, why hasn't it got them? Then we can just quibble about where the line of "large enough" is. Clearly 50/60mm aperture is large enough; 40 probably is too if you're willing to have it modestly longer, as I would be; 30, not so much.
If you check the old Hensoldt Dialyts, you'll find plenty of of models with smaller apertures. They're longer, of course, but very slim. All with AK prisms.

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Old Sunday 16th February 2020, 22:24   #40
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Bill, this is getting where I'd like to see this thread go.
We should also consider all prism types including Porro II, Perger etc.

There are only a few major factors to consider, with:-
Size/weight/packaging-offsets, and,
Transmission/micro-contrast/colour rendition
being among the main ones.

-snip-

.....
This would provide a better framework for analysis than 50 million people going around in circles with one 'I reckon' in response to another.

Chosun
Hi Chosun, Thanks for offering up some concrete thoughts. Far more solid than my own! I was conducting a Gedanken experiment to see how far it can go, even fantasizing of a subscription kickstarter project, to hire Kamakura to build an 'edition' of bins to an 'idealized' spec. Or use other means to convince one of the major players to produce a 'retro' custom bin... This is not a practical venture... but interesting.

Meanwhile, you're already thinking specifics..

Standardization. You've addressed an element of it with regard to thinking about prisms, but ahead of that might be agreeing on a format... 7x, 8x, 10x, - 30, 32, 35, 40 42, 50...

Here's a collection of random observations in response:


Prisms:
I was leaning towards Porro, partially because I bow to the experience and expertise around here that I lack. In addition, the simplicity of manufacture might offer an advantage in terms of cost and the opportunity for less things to go wrong...

Plenty of good minds here, but consensus on anything is not a hallmark of this place. I figured on just digging up what I could find on prisms to learn for myself the whats and the whys. There's so many folks who could probably address many issues you bring up straight away, and be done with it.

A few more things to chew on:
You've probably read up on Henry Link's experience with his 8x56 Zeiss Victory FL..achieving a certain optical nirvana by walking between the aberrational raindrops, so to speak...accepting the flaws of manufacture (Zeiss!) and simply reducing the amount by increasing the size of the exit pupil relative to the entrance pupil. A novel approach with a minor drawback: the bins need to be bigger for it to work. Trying to leverage that advantage into another format leaves me thinking: 6x42, 7x50... ?

Moreover, reading a range of comments over the last few months, including Henry's own well done textbook example of an optical evaluation of a binocular for one of the recent Kowa BD xII deluxe turbo something or other...

https://www.birdforum.net/showthread.php?t=384387

Even Henry points out that the wide resolution deficit between the Kowa and his reference standard, the Nikon EII, is probably not noticeable until one puts the binocular on a tripod. Basically, that handheld binoculars can get away with lower resolution, because it can't be detected by most people when used that way..

Listening to Chuck Hill try to tweaze out the optical differences between an Ultravid Silverline and a Noctivid in an entire day out birding, or Canip doing something similar in a Leica shop, comparing the new Trinovid to some others, supports Henry's assertion to some extent, and also tells me that this whole dialogue is exactly what Bill Cook accuses us of doing repeatedly: Stacking BB's and hair splitting, And I think he's right.

Doesn't mean its not fun, but there are a lot of practical realities to chew on...

First off, the current, excellent by most standards, performance of the top roofs is an indisputable benchmark. One can buy an existing product that is THAT GOOD. Drawback: costly.

Also on the market are products like the Habicht and the Canon IS lines, considered top optical performers by many, AND less expensive. Drawback: ergonomic dinosaurs, poor eye relief, narrow FOV on some models.

Then suppose we try to shoehorn Henry's optical strategies into this cauldron of variables...
What is the threshold of decreasing the exit pupil/entrance pupil ratio of performance advantage? I don't have a clue.

Simple example:
I've got a Carton 'Adlerblick' 7x50 binocular that I've owned for over 20 years. Orion sold them, advertised as long eye relief for glasses. Its got a 7 fov, weighs about 785 grams, and close focus is in the 7 meter ballpark. There's an
example of a 50mm Porro that has the weight of a portly 8x42 roof...A viable chassis perhaps to start with?

What if we bump up the specs to 8.25 FOV, close focus 3 meters, maintain eye relief @ 18mm, then how much bigger and heavier would it be? How much more glass does it take to widen, and better correct the field? What if we bump magnification to 8x50?
Would a 6.25 mm exit pupil be enough to grant the improved performance relative to a 7mm EP in daylight viewing? Inquiring minds want to know! (or not!)

Light Transmission: I'll go with a 3% minimum threshold for visual detection, based on some rational consensus on earlier threads I've read. Some of the top roofs are in the 94% range. Even the 7x42 Habicht at reportedly 96% won't likely be a detectable difference, just a numerical advantage on paper. If we aim for a wider field, we're probably adding more glass, which drops the transmission regardless of the prism size...

Attempting to fine tune color balance, flatten the curve, is an interesting endeavor. I have no idea which part of the system would make the most impact on it... maybe coatings.

Cat herding, BB stacking... consensus of format... consensus of anything...

That's all I got for today. I appreciate your interest and energy on the topic.

-Bill

Last edited by wdc : Monday 17th February 2020 at 18:00.
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Old Sunday 16th February 2020, 22:34   #41
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So how do rifle scopes and cameras manage this issue?
Is it not simply a matter of adding an extra lens?
SLRs have/had a prism in the housing above the lens mount. A digital viewfinder camera properly erects the image with software. Most riflescopes are roof prisms aren't they?

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Old Sunday 16th February 2020, 23:20   #42
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Most riflescopes are roof prisms aren't they?
That was the question, riflescope cutaways that I've seen do not show any prisms, just lenses.
I thought the inverted image is re-inverted via a second lens, but don't actually know, so am hoping someone will give a definitive answer..
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Old Sunday 16th February 2020, 23:54   #43
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That was the question, riflescope cutaways that I've seen do not show any prisms, just lenses.
I thought the inverted image is re-inverted via a second lens, but don't actually know, so am hoping someone will give a definitive answer..
A riflescope uses optics to erect the image with two doublet lenses. No prism's needed. If you are wondering why binoculars don't use this simple lens erecting system instead of heavy prism's here is a thread over at Cloudy Night's that explains why.

https://www.cloudynights.com/topic/6...-scope-design/
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Old Monday 17th February 2020, 00:07   #44
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Also note that scopes are 8-12" long. Bigger aperture ones weigh as much as a small binocular. Couple that with needing one for each eye.

Speaking of prisms I seem to recall the S-P coming out in 1899 and the A-K in 1905. I suppose that speaks volumes about the original design, but that seems like a pretty long stretch with no new prism types. Seeing what can be done with them, the R&D for new prisms may be overly expensive.
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Old Monday 17th February 2020, 03:00   #45
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A riflescope uses optics to erect the image with two doublet lenses. No prism's needed. If you are wondering why binoculars don't use this simple lens erecting system instead of heavy prism's here is a thread over at Cloudy Night's that explains why.

https://www.cloudynights.com/topic/6...-scope-design/
Thank you, that is an informative link.
It suggests that prism less designs may offer an opportunity, but the tradeoffs involved have kept prisms the more economical option.
I hope someone does build a prism free glass, thinking it might achieve both better eye relief as well as a wider FoV.
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Old Monday 17th February 2020, 05:27   #46
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I "WAS" (as in, past-tense now), gonna start & open a thread on several (TWO), brand-new sets of binoculars I've bought, which rather surprised me with their quality, put-up against their comparatively low-middling price.

(The company concerned are from Dresden in Germany & were more well-known for their cameras)
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I looked up binoculars made in Dresden, and could not find anything but antiques! So, you have some mystery bins, as far as I can tell.
Ah, a mystery... with Dresden and cameras I would have to guess Praktica, though at $30-100 most would call their binoculars simply "low priced". I've never seen one or read about them here, but they could be made in China, and therefore similar or identical to some other brands.

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Old Monday 17th February 2020, 09:13   #47
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Pracktica cameras are numerous in the U.K. I have had several, actually many.
They are basic, but worked well.

I suppose the 6x6cm Pentacon Six was also made in Dresden?
Again I have a fair number.
A low priced version of the 6x7cm Pentax SLR.
Interchangeable screens etc.
If the cameras are not wound on properly they can jam. They may jam if film is not in the camera when operated.
The machining is rather crude, but the Zeiss lenses were good.
50mm f/4 Flektogon high reputation image wise, 65mm rare, 80mm Biometer, 120mm Biometer less common, 180mm Sonnar, 300mm f/4 Sonnar.
Also the 500mm f/5.6, although mine seems to be f/4.8. It has pinched optics, but could be good if the lenses were freed up a bit.
I have taken the 80mm Biometer apart and the machining is rather poor. Some have Zeiss covered up on the front bezel with Aus Jena.
There were also Meyer lenses.

There were Pentacon 35mm SLRs of various types and I think rangefinder cameras also.
The attraction of these cameras was price.
These cameras are very numerous.

There are Russian copies of the Pentacon Six/Praktisix. There is a Russian medium format 30mm f/3.5 lens, Zodiak/Arsat.

With cameras the lenses form inverted images usually, so prisms are not necessary.
It is only the viewfinders that needed prisms or mirrors.
The Periflex had a small drop in erector.
The Wrayflex had a reversed image except the Wrayflex 3, which had a pentaprism. Mine didn't work. Rare.

With rifle scopes the relay lenses seem to have dust visible on the lens surfaces.
Russian spotting scopes often have relay lenses and often small fields.
Broadhurst Clarkson spotting scopes use relay lenses. The rear eyepiece and relay lens component makes a fantastic microscope, about 20x flat field.
Same with the terrestrial eyepieces for their astro refractors.

My Yukon 30x50 binocular is optically excellent. It uses mirrors not prisms, but is let down by poor lens coatings and ordinary mirrors. It could be very good if properly fully multicoated.
Mirrors would need to be high quality and there may be problems with light scatter.

I suppose some straight spotters use Porroprisms.
I used my 150mm Maksutov with a Porroprism adapter for terrestrial use.

Although my astro scopes were usually inverted image, I used prisms for terrestrial use.
Despite non phase coated adapters being condemned here, I find the views perfectly acceptable.

Similarly for astro use I find non phase coated binoculars perfectly acceptable also.

Later Practika or Practica binoculars seem indeed to be Chinese There are umpteen models. Badge engineering. The Praktica camera lenses are Japanese or maybe Chinese.

The best camera actually made in East Gemany was the 35mm full frame Pentacon Super possibly 1968 to 1972?
I see asking prices now of 2,500, but I don't know how much they actually change hands for.

After the Pentacon Super the Japanese camera technology was something Pentacon could not compete with.

Zeiss West made very good, but expensive cameras and of course Hassleblad in Sweden using Zeiss lenses.

I had a Zeiss Flektogon 20mm lens adapted to Minolta and it was indeed a good lens for its time.
However, Minolta's own 20mm might have been better, although I never had one.
I had the 16mm Minolta full frame fisheye, which I think was made also under the Leica name with final quality control by Leica.

B.

Last edited by Binastro : Monday 17th February 2020 at 17:04.
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Old Monday 17th February 2020, 12:11   #48
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A riflescope uses optics to erect the image with two doublet lenses. No prism's needed. If you are wondering why binoculars don't use this simple lens erecting system instead of heavy prism's here is a thread over at Cloudy Night's that explains why.

https://www.cloudynights.com/topic/6...-scope-design/
Not much room for a focusing lens.

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Old Monday 17th February 2020, 18:11   #49
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Not much room for a focusing lens.

Lee
Well, since this came up as a question concerning an optical system...They come with one of two focus mechanisms. One is to loosen a lock ring and turn the ocular bell. This is an excruciatingly slow focus and will take several turns to get right. There is a newer faster focus with a ring on the end of the ocular, marked + 0 - that turns much quicker. It moves the eye piece lens back and forth. There is, on some scopes a parallax adjustment that relies either on turning the objective bell. or in some newer models there is a knob on the side. The usual practice is to focus so the reticle is sharp. There is a magnification range of up to 5x, ie from 5-25x or 12-60x. FOV is narrower, since you are not scanning areas with them. They also have extended eye relief in the eye being placed several inches behind the ocular.

No prisms here, returning to the regularly scheduled programming.
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Old Tuesday 18th February 2020, 07:20   #50
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Well, since this came up as a question concerning an optical system...They come with one of two focus mechanisms. One is to loosen a lock ring and turn the ocular bell. This is an excruciatingly slow focus and will take several turns to get right. There is a newer faster focus with a ring on the end of the ocular, marked + 0 - that turns much quicker. It moves the eye piece lens back and forth. There is, on some scopes a parallax adjustment that relies either on turning the objective bell. or in some newer models there is a knob on the side. The usual practice is to focus so the reticle is sharp. There is a magnification range of up to 5x, ie from 5-25x or 12-60x. FOV is narrower, since you are not scanning areas with them. They also have extended eye relief in the eye being placed several inches behind the ocular.

No prisms here, returning to the regularly scheduled programming.
Thanks for this Steve,

I actually meant 'not much room for a focusing lens in what we would regard as the usual position, if you used this arrangement in a binocular', clearly if this is what I meant, this is what I should have posted

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