Largest AFOV ? (1 Viewer)

.... wider than I can easily see with my Televue Naglers in my 70mm APM bins... could take other well corrected Astro eyepieces instead. Wide, sharp as far out as I can see, quite compact eyepieces, but attached to bins you could use for weight training and individual focussing... so still a compromise.

Peter

Patudo said:

The two needn't be mutually exclusive. Moving the object found in your wide-field binoculars into the center of said view does the trick nicely.


To jring and Gijs; did the 6x24 Trinovid have Uppendahl prisms or a prism-mirror combo used in the other first generation Trinovids and the Amplivid? I thought (but please correct me if I am wrong) it was the latter setup that allowed such extremely large fields of view.

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Are you saying that the aberrations causing the image to grow softer at the edge of the field—mainly field curvature—do not exist near the center of the field or that they are largely undetected near the center of the field? There’s a difference. Sometimes That which can’t be readily detected can have deleterious effects overall. :cat:

Bill

And to pick up on Andy's point in post #16: 'Just go get the Nikon WX and end it there'

He's right of course, the WX gives a wide field of superb optical quality - but you pay for what you get, in many ways
As Bill indicated in post #5, it's always about trade-offs

> A photo of the 10x50 Nikon WX vs the 10x50 Swarovski EL SV!

(I also posted this image yesterday in the current Nikon WX thread: https://www.birdforum.net/showthread.php?p=3823693#post3823693 see post #63 for the source)

John

ceasar said:

When I am looking through any binocular I am conscious of its actual field of view and what I see inside it. I never give any thought about it's "apparent" field of view.

Bob

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Yes, that's the right conclusion - but the described 'actual field' depends on the AFOV of the eyepieces. Beside there is the circumstance of edge-sharpeness - or if this is bad, the AFOV is too big for the combo 'eyepiece-prism-objective' or has to be limited (a little) with field-stops in the way of light.

Manfred

bioscope said:

Yes, that's the right conclusion - but the described 'actual field' depends on the AFOV of the eyepieces.

Manfred

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This is where I need some help Manfred because AFOV seems misleading sometimes. For example Zeiss claim the AFOV is the same 64deg for both SF 8x and SF 10x but the real field for the 8x is 148m at 1km whereas for the 10x this is only 120m.

Lee

Hi,

a rough way of calculating this is

afov in deg = tfov in deg x magnification

This assumes no distortion which is not usually correct.

tfov in m/1000m = tfov in deg x 17.45

Joachim

Re. my post #20.
Does anybody know if the Amplivid and Bresser SWA binoculars have similar mirror prisms?
Are the Amplivid mirrors flat and the Bresser Super Wide Angle mirrors curved?
Are the mirrors in the same position?

The Bushnell 4x21 Xtrawide may be another mirror prism binocular. I can't remember.
It is actually about 3.5x21 so the field is much less extreme than the Bresser SWA and the view is quite good except for a very curved field. I cannot accommodate this, but children seem to like this binocular.
The other Bushnell Xtrawides have normal prisms I think, except the 4x30, which seems to be the same as the 4x21.

Are there other mirror prism binoculars, civilian or military?

Hi,

I don't know if it is the same construction, but the Besser SWA seemed to use prisms and mirrors. See this article on binomania.

https://www.binomania.it/bresser-7x32-swa-135-di-campo/

Joachim

Thank you Joachim.

A British T.V. technical show rated these as good as a Canon 10x30 IS.
I lost any respect for these so called technical presenters.
But the whole importation of Bresser SWA sold out in about two days because of their review.
I had great trouble finding one.
They were also made in 8.5x and 10x with the same back portion, but different ocular tubes.
Also sold as Ascot, Orion? etc.

As to the reference above I put it on translate, which had some interesting effects. I don't speak Italian.

I have to agree with the following, hopefully it is O.K. to give short references.

Real sharpness 50%, to be generous, the rest is a salad of all known aberrations.
I love this description, and this is accurate.

Star clusters.
Breathtaking! but beware... . quelle? you see the edges are not stars, but galaxies with a coma of fear!
Yes, indeed.

Conclusions.
An extremism, a virtuoso viewing wide field that transcends any ambitions of optical excellence.

This reference is copyright of Binomania. Any mistakes are my own.

I think that the Amplivid and Bushnell Xtra wide 4x21 use similar systems, but would like to know how they differ from the Bresser SWA.

Regards,
B.

Hi,

I also used Google, my italian is nonexistent too.

I think we didn't miss a lot by not getting a pair...

Joachim

WJC said:

Are you saying that the aberrations causing the image to grow softer at the edge of the field—mainly field curvature—do not exist near the center of the field or that they are largely undetected near the center of the field? There’s a difference. Sometimes That which can’t be readily detected can have deleterious effects overall.

Bill

Click to expand...

I'm saying that, with regard to your earlier assertion that "the observer must determine which is most important, locating the subject—possibly in flight—or identifying and enjoying the subject once found", it's quite possible to identify and, indeed, to enjoy objects with a wide-field binocular - especially if one moves said objects into center of field of view after finding them. :cat:

Patudo said:

I'm saying that, with regard to your earlier assertion that "the observer must determine which is most important, locating the subject—possibly in flight—or identifying and enjoying the subject once found", it's quite possible to identify and, indeed, to enjoy objects with a wide-field binocular - especially if one moves said objects into center of field of view after finding them. :cat:

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Hi, Patudo:

We are all products of our environment and experiences. Sometimes those experiences clash with the experiences of others who haven’t had occasion to walk in someone else’s shoes. Neither is bad, just different. I certainly agree with YOUR last assertion. But you’ve had a sheltered optical life if you haven’t met observers who want binoculars with a tremendous FOV even though most of that field is pure garbage.

You say the observer can merely move the subject to the center of the field. In speaking with MOST of the members of BF, I’m sure that’s true. But spend day after day for years trying to help those steeped in misguided opinion and fraudulent advertising and perhaps and you might have more tolerance for differing experiences. I once sold an Astroscan 4.25-inch telescope to a fellow who had just gotten rid of his 17.5-inch Coulter Dodsonian because, “All the stars just look like little dots.” He wanted all the stars to be magnified. I’m sure the guys running the Hubble would like the same thing. I tried to explain, but his want overshadowed rational thinking.

Have a look at the photo of the 120x120 (really, a garden variety 7x50) attached. Perhaps it would not sell to you or any of YOUR friends. But you may rest assured that the fraudulent text on the backplates insured plenty of sales to the inexperienced and gullible. Big numbers make cash registers ring, whether speaking of magnification or FIELD OF VIEW. By the way, that 120x120 binocular had an 11-degree field of view. At least that's what it said on the backplate. But I guess that wouldn't matter since the 120 power 50mm bino would provide less than a 1/2 degree FOV. And with image brightness being based on coverage on the retina, the image would be so dim the field wouldn't matter much. What month is it that pigs fly? And with most of THOSE INSTRUMENTS, placing the subject in the center of the field sometimes makes little difference. As Paul Harvey used to say ... “It’s not one world.” :cat:

Bill

Hola, WJC:

There would seem to be remarkably little interest in instruments similar to the one you posted here; my guess is that Birdforum folks - though maybe unschooled in the intricacies of such things as Seidel aberrations - are still much more likely to be amongst those who know that targets are best identified and enjoyed with a wide-field binocular by being placed in the center of the field, than those who would rush out and buy 120x120s with an 11 degree field of view.

I - as many others here have done, I'm sure - have had the dubious pleasure of having dealt with the general public in the past, but find it far more enjoyable to express myself here as I might amongst those who share the enjoyment of birds and binoculars. At the same time, one may certainly appreciate that an individual whose optical world-view was warped, I mean shaped, by decades of explaining the ins and outs of things optical to the "inexperienced and gullible" might find it hard to alter the habit of a lifetime. But whatever may be the case, I applaud your unstinting efforts to protect the untutored masses from the twin evils of marketing and hype, and wish you all success in preaching the gospel of holy collimation across the internet. :cat:

Regards,
P.

Patudo said:

Hola, WJC:

There would seem to be remarkably little interest in instruments similar to the one you posted here; my guess is that Birdforum folks - though maybe unschooled in the intricacies of such things as Seidel aberrations - are still much more likely to be amongst those who know that targets are best identified and enjoyed with a wide-field binocular by being placed in the center of the field, than those who would rush out and buy 120x120s with an 11 degree field of view.

I - as many others here have done, I'm sure - have had the dubious pleasure of having dealt with the general public in the past, but find it far more enjoyable to express myself here as I might amongst those who share the enjoyment of birds and binoculars. At the same time, one may certainly appreciate that an individual whose optical world-view was warped, I mean shaped, by decades of explaining the ins and outs of things optical to the "inexperienced and gullible" might find it hard to alter the habit of a lifetime. But whatever may be the case, I applaud your unstinting efforts to protect the untutored masses from the twin evils of marketing and hype, and wish you all success in preaching the gospel of holy collimation across the internet. :cat:

Regards,
P.

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Que pasa, Patudo:

— There would seem to be remarkably little interest in instruments similar to the one you posted here;

I am aware most of the members of BirdForum are a cut above. But I can’t focus my thoughts exclusively on optically endowed people. I am aware there are those here who are academically MILES ahead of me: David, Henry, Ed, others. Heck, sometimes I will even pay attention to what ... Gijs has to say. 8-PThat doesn’t mean the lowly practitioner has no place in the puzzle. Even a broken clock is accurate twice a day.

The “similar” instrument you speak of was ONLY AN EXAMPLE. I realize most people are using roof prism binos today. I also know that snake oil selling techniques still abound. BF members are by and large above the problem. But the problem is still out there. And as long as people see distortion and call it field curvature, see a collimation error and say their binocular won’t FOCUS, use depth of field in the vein of PERCEIVED 3-D imaging, or believe the light grasp of their bino is equal to the surface area of BOTH objectives, it will remain so. Some people find it far easier to pontificate on unscientific opinions than spend a little time researching the facts. In so doing, the honest truth-seeker can get easily sucked into a non-productive rabbit hole.

I teeter on the fence of knowing whether you understand my thinking or not. Either way, it doesn’t matter. What people think of Bill the old optician is of no importance. What they might learn through his many ramblings is very important, at least to those who give more than lip service to wanting realistic answers to their sincere questions.

With “... in preaching the gospel of holy collimation across the internet,” I get the impression you think I’m a one-note singer. Actually, when it comes to binoculars, I know ... TWO NOTES.

People expend 10s of thousands of words a year talking about things that annoy them: small fields of view, inadequate eye relief, grazing glare, “squared” exit pupil, curvature of field, excess lateral color, and MANY other things. The fact is that all their words are not going to change one of these problems one iota! The problem can only be solved through the transfer of some of those little colorful pieces of paper found in the wallet.

COLLIMATION IS THE ONLY ANOMALY THAT CAN BE ADDRESSED BY THE INDIVIDUAL. Thus, I am of the opinion that the observer SHOULD be willing to learn the scientific method for solving that problem. Is that so wrong of me? The Internet has many sites portraying the solution to the problem. However, as of this date NOT ONE IS ACCURATE. YEP, YOU CAN QUOTE ME ON THAT. They all deal with conditional alignment, and nothing more. If the error is minor and the observer’s spatial accommodation great, that might be all that is required ... if the bino is to be used by one observer or others with the same IPD. HOWEVER, IT IS NOT COLLIMATION!

But do those passing off this bad information know that by following those instruction alignment could be made worse or that the instrument COULD be damaged? “WHAT ... DID I DO THAT?”— Steve Urkel.

Yes, Patudo, I beat the drum as loud as I can. I have to just to make even a DENT in the foolish, untutored bull that is awash on the Internet. If you think my feelings are too close to the surface, you’re not alone ... I DO TOO! But after four decades for monograms, articles, lectures, and books my nerves are a little raw. I WANT to help those who want to be helped. But in order to do so, I find I must scale the never-ending wall of misinformation, some of which is innocently put forth, while others offer it as if they have just devised a sure-fire 10-minute brain surgery technique.

I keep seeing how “easy” it is from people who are absolutely CLUELESS on the subject.

Is it easy? For someone who KNOWS what he’s doing ... yes, it is!!!

For all others, no it isn’t. Understanding the procedure for performing 3-axis binocular collimation would take a whole page to page and a half and 6-7 minutes to read and think about. But with so many members of bino forums caring as much for opinions as facts, I have a hard row to hoe. Please don’t think the worst of me for trying to help my neighbor. The guys at the Center for Optical Sciences and SPIE think my opinion might just a touch better than the one that now graces the Internet. :cat:

Cheers,

Bill

FWIW my older son has a PhD in Physics and last year he taught an upper division course in Optics at the college where he is an Assistant Professor of Physics. I doubt if they studied in depth much of anything that we discuss here on a daily basis but I will check with him when he comes home on spring break.

Bob

PS: I did give him my Swarovski SLC 8x30B binocular because it worked well with the eye glasses he wears.

ceasar said:

FWIW my older son has a PhD in Physics and last year he taught an upper division course in Optics at the college where he is an Assistant Professor of Physics. I doubt if they studied in depth much of anything that we discuss here on a daily basis but I will check with him when he comes home on spring break.

Bob

PS: I did give him my Swarovski SLC 8x30B binocular because it worked well with the eye glasses he wears.

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Hi, Ceasar:

As many of my friends have PhDs in optics as without. To most of them, the things we often discuss are way below their day-to-day fare, and binocular collimation leads the pack.

The graphic attached came from a conversation with a professor of both precision and ophthalmic optics at the U of A, a fellow originally trained in optics at the University of Rochester. Getting him to understand the concept of conditional alignment is how I was invited to speak at an SPIE conference. I was just that broken clock. But I had a piece of the puzzle most of the postdocs had never considered because they had no reason to—preposition at the end, and all.

But then, the original comments were about a wide field of view, the lower quality at the edge of that field, and how all can be overcome by placing the subject in the center of it. For MOST OF this group, that is a great idea.

But, more often than not, my GENERAL comments are directed to those new to binocular observing or who are just passing through.

In the mid-90s, a fellow came into Captain’s wanting a binocular with a greater than 11-degree field of view. He said he had one of those out in his car and he wanted more—field of view, that is. I didn’t recognize the brand. It appeared to be one of the myriad brands mass produced for hardware, novelty, drug, and regional sporting goods store in the States.

The fellow was very proud of his possession. On looking through the binocular, I could not only see that it didn’t have an 11-degree field but that the center of that field left a lot to be desired. I told the owner I had doubts about the 11-degree field and asked if he minded me placing it on the collimator.

The collimator—graduated in degrees and minutes—revealed the edge-to-edge field was 7.5 to almost 8 degrees. My customer decided I was not capable of helping him find a binocular with a larger field. After all, how could a graduated collimator hope to compete with the verbiage emblazed on the binocular’s backplate? Verbiage put there by ... optical professionals.

Sometimes, try as you will, you can’t save SOME people from themselves—like the fellow who found problems with his 17.5-inch Dobsonian because it wouldn’t MAGNIFY STARS. Anyone who thinks I am blowing smoke can ask Cory; he was working with me at the time.

Finally, I applaud anyone with sense enough to move their quarry to the center of the field. I would only hope they would recognize that all centers of all fields are not created equally and that the intellects of all observers aren’t created equally, either.

“The truth is incontrovertible. Malice may attack it. Ignorance may deride it. But in the end, there it is.” —Winston Churchill

“Politically correct, or not.” —Bill Cook

Bill