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Prisms! S-P, Uppendahl, Abbe-Koenig.. (1 Viewer)

Gijs: I didn't forget them ... :king: I've got three of them myself, and they're excellent. In fact, I'd rate the 10x40 optically as better in the image center than any 10x roof I'm familiar with.

However, to qualify as "excellent, modern porros" they'd need a couple of upgrades:

- Slightly more modern eyepieces that provide a bit more eye relief and, in the case of the 10x40, a slightly flatter field. The old Erfles of the 10x40 don't cut it anymore.

- Somewhat bigger fields of view, especially the field of view of the 7x42 (optically a killer binocular!) is definitely too narrow.

- A smoother focuser, so they'd need a different way of making them waterproof or at least splashproof. Zeiss used rubber seals in the porros of old making the binoculars at least splashproof, their focusers were great.

That would do nicely, I don't need screw-out eyecups or very close focusing distances.

Hermann

Yes to all those suggestions..... except I'm not sure about the eyecups. If there's enough eye relief for the likes of me, others will probably need to back out the eye cups.

My benchmark for close focus is whether I can hit the bird feeder from the kitchen! Non-negotiable!

-Bill
 
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I'm posting a link to a BF thread from 2006, which includes some current contributors on the forum, who are tolerant enough to still post here. I've read through this thread twice, because its really informative, articulate, and generally represents folks being their best selves as well. Whats surprising is that in 14 years there have not really been any big technical advancements in optics, as it applies to what is currently on the market, from what I can tell.

The comment on light transmission perception thresholds are particularly informative, as they may play into why manufacturers have gone down certain roads leading to today's products.

Enjoy, and thank you Henry Link, Bill Cook, Elk Cub, Pileatus,and Pinewood, (among others whom I'm not familiar with)
for contributing to this thread.

https://www.birdforum.net/showthread.php?t=63770

I think most of us on that old thread have learned a few things about optics since 2006, but if it isn't obvious already I would caution newbies to take the long rambling posts from ksbird/foxranch with a very big grain of salt. If they seem a bit off it's because they are a bit off. He/she/they (I was never sure which) was/were the first of several posters down through the years who seem to have come here from some parallel optics universe with fantastical stories and ideas to share with us. You might say the Rico70 of their day. ;)

Henry
 
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Whats surprising is that in 14 years there have not really been any big technical advancements in optics, as it applies to what is currently on the market, from what I can tell.

First, a minor correction: There has been little meaningful progress in binoculars since mid 1990's (introduction of Zeiss Design Selection series, Leica Trinovid BA series). That's nearly 30 years of having "nothing new" yet "us talking a lot" about binoculars B :) Second, it is not surprising. The minimum value of an "error" is zero. You cannot minimize binocular errors (we call them aberrations) indefinitely. Third, search for new horizons; you shall find "hope" there ;)

-Omid
 
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Yes to all those suggestions..... except I'm not sure about the eyecups. If there's enough eye relief for the likes of me, others will probably need to back out the eye cups.

Actually, there was a time when some manufacturers offered rubber eyecups in different lengths.

Problem solved.

Hermann
 
First, a minor correction: There has been little meaningful progress in binoculars since mid 1990's (introduction of Zeiss Design Selection series, Leica Trinovid BA series).

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.

With roofs it's different, before the introduction of phase-coatings in the late 1980s they were pretty awful by today's standards.

Just for fun an excerpt from the archives of Peter Abraham's mailing list (http://www.europa.com/~telscope/binotele.htm):

"I got my first pair of roof prism binoculars with phase-coated prisms, a pair of Zeiss 8x30B's, immediately after Zeiss started selling them, and I found the difference in direct comparisons to older Zeiss 8x30's quite marked. It was basically just as Weyrauch/Doerband had written in their paper - better resolution, slightly higher contrast, overall a "more pleasing image".

Last autumn I finally had a chance to do a more detailed comparison. We (a couple of fellow birders and I) got together for a weekend trip, and as there wasn't much about we had the time to do a detailed comparison of three different Zeiss 10x40B's. The first one was bought in 1979. It doesn't have T* coatings and the prisms are not phase-corrected. The second one was bought in 1981, with T* coatings but still without phase-corrected prisms. The third one was purchased in 1998, so it has both T* coatings and phase-corrected prisms.

The interesting thing about this comparison was that all three binoculars were of the same make and had the same specifications, so all the differences observed were caused by the different coating technologies used. We compared the binoculars mounted on tripods, checking for their optical quality by looking at birds and a Zeiss standard resolution target in a variety of light conditions.

Perhaps the most interesting result initially was that the differences between the two old Zeiss 10x40B's weren't all that great. Sure, the T*-coated pair had slightly better contrast with cleaner colours and a slightly brighter image, but the difference was nothing to boast about. Even under difficult lighting conditions the difference wasn't that great. The resolution was exactly the same (as it should be), and the image of both was slightly fuzzy. This was most noticeable when checking the resolution targets.

The comparison with the pair with phase-corrected prisms was almost a foregone conclusion after these results. And sure, it had much better contrast and cleaner colours, a brighter image and quite clearly a higher resolution than either of the two pairs without phase-corrected prisms. In fact, the difference was nothing short of amazing.

I believe this comparison puts some of the claims made about modern multicoatings into perspective. Modern multicoatings are nice, but they're not the most important thing to watch out for in roof prism binoculars. Based on this comparison I'd say the most important progress has not been the development of modern muticoatings, but rather the development of phase-correction coatings on the prisms.

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."

That excerpt is slightly abbreviated, I left out one paragraph.

Hermann
 
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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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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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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
 
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
 
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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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 ! :-O

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. :cat:





Chosun :gh:
 
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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.
 
Depends on how you define "significantly" ... :king:

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... ;)

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...

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.
 
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
 
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.
 
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?
 
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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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.

Hermann
 
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. :cat:

Chosun :gh:

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. :t:

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
 
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