Where are the aspherics? (1 Viewer)

[opisska]

Observers would not want a 24mm binocular to be as long as the 8x56.
But at f/8.75 the performance would be good.
.

If that's true than said observers have only themselves to blame for having to lug around a heavy binocular needlessly, right?

But I am happy that I was able to put my point forward that the performance of binoculars is not strictly limited by the lack of aspherical elements ...

This reminds me of the sad fact that there are no binoculars on the market that I would know about without rectified image. Imagine how lightweight yet optically great bins you could get if people were just willing to accept seeing the world upside down. It's not even hard to get used to it to the point of basically ignoring the fact after some time, but alas.

 

[Canip]

What do you mean by „without rectified image“ - no prisms?
There are some ...

 

[tenex]

But I am happy that I was able to put my point forward that the performance of binoculars is not strictly limited by the lack of aspherical elements ...

I see I missed your point because I was speaking of binoculars that people would actually want to buy and use in the real world, not long narrow tubes with small exit pupils. I never suggested that "performance is strictly limited by lack of aspherics", only that their addition could be the most practical way of improving it, as demonstrated by the construction of modern camera lenses.

 

[opisska]

I see I missed your point because I was speaking of binoculars that people would actually want to buy and use in the real world, not long narrow tubes with small exit pupils. I never suggested that "performance is strictly limited by lack of aspherics", only that their addition could be the most practical way of improving it, as demonstrated by the construction of modern camera lenses.

I was simply reacting to the problem set up in the first post of the thread. Where the poster complains that for good viewing quality someone is forced to carry around a heavy binocular, the weight of which is practically useless, because he uses is in broad daylight where his eye pupil is small. "Long narrow tubes with small exit pupils" are the exactly right solution to this problem, so this particular chap would clearly want to use such thing in the real world, wouldn't he?

What do you mean by „without rectified image“ - no prisms?
There are some ...

Really? I have never found any - not that I did research intensively, but I have looked through the offers of local vendors. Could you provide some examples?

 

[Canip]

.....
.....
.....
Really? I have never found any - not that I did research intensively, but I have looked through the offers of local vendors. Could you provide some examples?

Basically all Galilean type binos, i.e. what’s called „opera glasses“ of all kinds, plus astro gear like the following:

https://www.astroshop.de/geraete/vi...MI1tiP3d-35wIVBc93Ch1oRAKTEAAYASAAEgLMkvD_BwE

https://www.omegon.eu/de/geraete/omegon-fernglas-2-1x42-fuer-sternfeldbeobachtung/p,50354

https://agenaastro.com/kasai-trading-wide-field-binoculars-28-true-field-view.html

https://agenaastro.com/astro-hutech-hinode-wide-field-binocular.html

 

[opisska]

Basically all Galilean type binos, i.e. what’s called „opera glasses“ of all kinds, plus astro gear like the following:

https://www.astroshop.de/geraete/vi...MI1tiP3d-35wIVBc93Ch1oRAKTEAAYASAAEgLMkvD_BwE

https://www.omegon.eu/de/geraete/omegon-fernglas-2-1x42-fuer-sternfeldbeobachtung/p,50354

https://agenaastro.com/kasai-trading-wide-field-binoculars-28-true-field-view.html

https://agenaastro.com/astro-hutech-hinode-wide-field-binocular.html

Oh sorry, that's not what I meant. Galileans are usually not very good especially if you ask them to do any real magnification; it's just another price to pay for an upright image. I was thinking about normal Keplerian telescopes without prisms, where you see the original view, that is, upside down.

 

[jring]

But what is stopping anyone to produce the same binos but cut down to the effective aperture? Where would be the aspherics needed in that?

Hi,

as has been pointed out, a pair of 8x24 with an f8.75 objective would certainly be optically quite good due to the relaxed focal ratio. But people would probably not buy it... at least not for bird watching... maybe some stargazers - some still value their slow focal ratio Fraunhofer or Newtonian for great planetary views...

Also some aberrations of optical elements (turned down/up edge) only happen at the edge of the lens or mirror, so a bit of stopping down is always a good idea... When stopping down a 56mm objective to 24mm, you will probably also eliminate most zones if there were any...

Joachim

 

[Binastro]

To make a Keplerian binocular one only needs to get a couple of 8x50 or 9x50 telescope finders and mount them on a plate.
Assuming the tubes are not too thick.

I have no trouble with upside down images and right way up images within seconds of each other, although to read distant text it would be better if I stood on my head. The extra blood might improve my night vision

My 30x50 Yukon folded refractor binocular has excellent star images and fine resolution.
The problem it has is poor coatings, or lack of coatings on the lenses, and ordinary mirrors instead of enhanced mirrors.
The alignment is good both between barrels and in each barrel.
If made with high end coatings it would be much better.
As it is the transmission is low.

I probably have a good example as Yukon quality varies a lot.

B.

 

[tenex]

I was simply reacting to the problem set up in the first post of the thread. Where the poster complains that for good viewing quality someone is forced to carry around a heavy binocular, the weight of which is practically useless, because he uses is in broad daylight where his eye pupil is small. "Long narrow tubes with small exit pupils" are the exactly right solution to this problem, so this particular chap would clearly want to use such thing in the real world, wouldn't he?

"The poster" is me, and while "this chap" (Henry) might well prefer on a sunny day to be carrying your hypothetical skinny bino rather than his full 8x56 due to weight, no one would actually be likely to buy such a thing given its limitations in other circumstances. It simply is not the preferred solution to the problem, any more than Henry's 8x56 is, so most people just live with an avoidable degree of aberration.

To get back to reality (again), I've asked why aspherical elements aren't found in higher-end binos today as they are in photographic lenses, and it would simply seem that... no one knows. Quality camera lenses trade on measured performance; binoculars, on mystique.

 

[Alexis Powell]

A random observation: Nikon has touted use of aspherical elements in some of its cheapest porros and some past reverse-porros (8x and 10x Diplomat) but not mentioned such use in its best bins. One thing all Nikon bins marketed with aspherics have in common is very sharp on-axis views, but another thing they have in common is awful performance outside their small sweet spot. Such implementation has not left me impressed.

--AP

 

[Binastro]

O.K.

The reason why aspherics are not used on Alpha binoculars.

It is much more difficult to make a good aspheric surface than a good spherical surface.

Using an aspheric component perhaps on the field lens of the eyepiece, plastic or glass, is much more tolerant than trying to make aspheric surfaces on the objective.

Even if made well on the front end the tolerances are much tighter with positioning aspherics compared to spherical surfaces.

Designers avoid aspherics if they can.

On camera lenses with certain elements aspherical surfaces can be used.
But front aspherics like on 50mm f/1.0 lenses probably means a £10,000 lens.

Aspherics is mainly an advertising slogan, but to designers of top quality optics is something to be avoided if possible.

I was told about small bundles of rays etc., but am not sure enough to quote accurately the reasons why designers are very reluctant to use aspherics except in specific locations.
An hour's discussion.

B.

 

[henry link]

All the claims for aspherics in binoculars I can find concern correction of off-axis aberrations in the eyepieces. None appear to have been used in the objective lenses to reduce spherical aberration.

This quote from an old CloudyNights thread is the most complete representation of Minox's claims for its old aspheric binoculars I found.

https://www.cloudynights.com/topic/23812-aspheric-lenses/?p=306716

My English translation of that is that molded aspherics were used to try to equal the off-axis corrections of 4 or 5 element eyepieces with only 3 elements. Nikon and Pentax make similar vague claims of better edge sharpness for their aspheric models, but no claims of reduced spherical aberration. Minox appears to have dropped their models completely, while Nikon confines aspherics to their cheapest lines, probably to reduce cost by using one plastic aspheric lens to replace two spherical glass ones. Pentax continues with their same old aspheric models (with new names) that were first introduced over 15 years ago.

Meanwhile, the real improvements to off-axis corrections in binoculars have come from more complex eyepieces with 6 or 7 spherical lenses, not 3 to 5 element aspherical eyepieces.

I don't know anything about aspherics in camera lenses, but a little Googling today turned up mainly claims for better edge sharpness, and the benefit of replacing several spherical lenses with just one aspheric lens, just like for binoculars.

 

[tenex]

Binastro, Alexis, Henry,

Good point about aspherics being more practical toward the back end (whether in lenses or binos) than the objective. And yes, it does sound like Minox and a few others used cheaper molded ones as a shortcut to simplify the ocular, rather than to further refine it, with unimpressive results.

As I reflect on the tenor of Binastro's comments I suspect that they refer to an earlier period of optics when aspherics were in fact extremely difficult to produce (by hand) and designers did avoid them. Today I imagine that both design and production must be more highly computerized and automated.

In any case ASPH elements do seem to be successfully produced and effective in camera lenses, and I remain curious why they wouldn't improve the performance of higher-end binoculars in the same way.

 

[Binastro]

The only possible front aspherised binocular I may have heard of is the Zeiss 8x60, which would cost close to £20,000 today.

I am talking about current designers using highly sophisticated computerised machinery with my comments above regarding aspherical elements.

The top lenses with aspheric components being produced are £10,000 to about £120,000.
Only Hollywood, T.V. companies or the military can afford them.

It remains that producing front end asherised optics is avoided by current optics designers.
In fact, Britain has a good history of aspheric machinery, although this has shifted to the U.S.A.

Aspherics are a bl--dy nuisance is the current thinking by those involved.

An honest advert would read. 'Our top end binoculars only use high quality spherical or flat optical components. We don't use aspherical components'.

But that is not what the public wants to hear.

B.

 

[fazalmajid]

The top lenses with aspheric components being produced are £10,000 to about £120,000.

Ground aspheric elements are somewhat rare and expensive, but the Nikon Z Noct 58/0.95 S uses them and is $9000.

It's considered an insane statement lens, the photographic optic equivalent of the WX binoculars. Most aspherics are used in telephoto lenses and high-end standard lenses that are far below in price.

Lenses with aspheric elements (usually plastic or glass-molded) start for as little as $100:

Even Leica makes a 28/2.8 Elmarit-M ASPH for as little as $2600

 

[tenex]

Ignoring the "insane statement" $9000 Noct which has 3x ASPH elements (including the front), here's the number found in the other recent Z-mount mirrorless lenses some of which sell for as little as $600-800, courtesy of nikon.com:

24mm f/1.8 -- 4x
35/1.8 -- 3x
50/1.8 -- 2x
14-30/4 -- 4x (2 in front!)
24-70/2.8 -- 4x
24-70/4 -- 3x
70-200/2.8 -- 2x

Only 1 Nikon Z lens so far does not have ASPH elements, the 85mm f/1.8. And they're consistently reviewed as improvements on their existing F-mount counterparts (although aspherics may not be the only reason).

 

[tenex]

I have the sense that we didn't get very far with this. Exotic glass types are widely used today both in photographic lenses and in binoculars, and advertised accordingly. Aspherical elements are also ever more widely used in even modestly priced lenses, while there have been few claims for their use in binoculars, none from alpha brands -- and one would expect patent applications to reveal their use even if not advertised for some reason. I think this requires explanation. Could it be that their real purpose in camera lenses (just as in those Minox oculars) is more to simplify the design than to produce a better image than can be achieved conventionally? Otherwise the only notable difference I see is that cameras record an image that can be enlarged at will and scrutinized afterward, while binos simply interact in real time with eyes that may have aberrations of their own, so manufacturers might think that for the average person at least, what can be achieved without ASPH elements is good enough.

Basically I'm (still) frustrated by hearing conflicting things about ASPH elements. I'm told that they're impractical to produce, but I see them all over the place today. I hear that they yield sharper results, and have seen and used new ASPH versions of lenses myself that outperform their predecessors. But I also hear that equivalent results can be obtained with conventional elements (just more of them) so "ASPH" is only marketing hype. I'd like to understand better what's going on.

 

[Chosun Juan]

A bit of all of that, and other points that Bill, Binastro etc have made earlier in the thread.

Manufacturers don't do what is possible - only what is necessary, and what is economically profitable.

In many cases designing and supplying product that is just 'good enough' is not going to take advantage of the technical advantages - it's like putting Ferrari titanium valves in your mum's Toyota Corolla shopping trolley - you aren't going to notice a jot of difference. The overall design is the major factor of influence.

If aspherics are limited by cost to moulded, plastic, or finished to a perfunctory level then the differences may not be noticeable or confer other benefits such as a simpler lighter optical train, and/or better control of aberrations, etc.

I'm sure manufacturers aren't even giving us as much resolution as is possible - they have set the design bar low. I want binoculars so sharp that they have to come with mandatory consumer advice - WARNING: Resolution so sharp it may cut your eyeballs ! :eek!: :-O

Just going from memory (always a dodgy thing to do ! there are aspheric ranges made by Minox, and I have a vague recollection of an aspherical element in the x32 Zeiss FL's which would be mentioned in the advertising somewhere (Zeiss are world famous trumpet blowers !

Enough for now .... need chocolate :eat: o





Chosun :gh:

 

[Troubador]

Zeiss's Harpia 95 has an aspheric element in the eyepiece.

Lee

 

[moyang_mm]

Basically I'm (still) frustrated by hearing conflicting things about ASPH elements. I'm told that they're impractical to produce, but I see them all over the place today. I hear that they yield sharper results, and have seen and used new ASPH versions of lenses myself that outperform their predecessors. But I also hear that equivalent results can be obtained with conventional elements (just more of them) so "ASPH" is only marketing hype. I'd like to understand better what's going on.

I may be wrong as I am not an optical engineer.

I think one reason that ASPH elements are more common in photographic lenses than in binoculars is that sensors in DSLR/mirrorless cameras are much bigger than "sensors" (human eye) of binoculars. The pupil of an eye is at most 7mm, but a APS-C sensor is 25x17mm. Smaller "sensor" means less off-axis light, hence less correction for spherical aberration required.

Also our eyes are pretty lousy optically. It is just a single-element lens. But we have the most advanced image processing system, the brain, that magically mitigates all the optical issues of the eyes. This could also explain why binoculars use less sophisticated optical formulas, because the brains have already addressed some of the aberrations.