Please read if you are about to buy high end bins (1 Viewer)

Hermann, what you say makes sense to me and I have experienced it myself. There are exceptions for me - I still cant explain why I get more black outs in bright conditions with my 10x40 zeiss, than my 8x20hg nikons. Maybe it has to do with the eyecups designs. I dont wear spectacles yet , which raises a niggling concern I have had for some time. What happens if I have to start wearing them one day, and all my carefully selected and much loved bins suddenly are most unsuitable! Has anyone had this experience?

I think it has been mentioned before, but blackouts are often because the eyecups are not set correctly, and your eye is either closer to or farther away from the eye lens than the exit pupil is.

Clear skies, Alan

mike60 said:

Hermann, what you say makes sense to me and I have experienced it myself. There are exceptions for me - I still cant explain why I get more black outs in bright conditions with my 10x40 zeiss, than my 8x20hg nikons. Maybe it has to do with the eyecups designs. I dont wear spectacles yet , which raises a niggling concern I have had for some time. What happens if I have to start wearing them one day, and all my carefully selected and much loved bins suddenly are most unsuitable! Has anyone had this experience?

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I have always worn glasses so I haven't had to adjust as you might have to but I can confirm that when you do wear specs eyerelief is critical. I've found I need at least 17mm to feel comfortable but obviously these things are very individual. I think the 10x40 Zeiss are 16mm.

I think that it is very much back to basics, with the correct setting up of the binoculars.

Get your PD correct, then the eye relief. Min 15mm eye relief should be o.k for spectacle wearers, but this can also be dependant on the individuals themselves (thickness of frames, where do you position them, type of lens, the individuals eyes (deep set etc). I have found that in most cases (not all) the basic setting up of the binoculars will overcome a lot of the problems.

mak said:

I think that it is very much back to basics, with the correct setting up of the binoculars.

Get your PD correct, then the eye relief. Min 15mm eye relief should be o.k for spectacle wearers, but this can also be dependant on the individuals themselves (thickness of frames, where do you position them, type of lens, the individuals eyes (deep set etc). I have found that in most cases (not all) the basic setting up of the binoculars will overcome a lot of the problems.

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Mak,

I think I know well enough how to set up a pair of binos after all of these years :eat: . Your comments about individuals are spot on. Personally, I have never felt comfortable as a specs wearer with 15mm eye-relief such as Swaro 10x42 SLCs or indeed the latest 8 x32 ELs. 16mm is ok but 17mm + very much better.

Blincodave said:

Mak,
I think I know well enough how to set up a pair of binos after all of these years :eat: . Your comments about individuals are spot on. Personally, I have never felt comfortable as a specs wearer with 15mm eye-relief such as Swaro 10x42 SLCs or indeed the latest 8 x32 ELs. 16mm is ok but 17mm + very much better.

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Blincodave.
I could have put it better, my comments were not directed at anyone in particular. I believe that the simple set up of binoculars, is maybe overlooked.

I do not always think about the set up until I notice an apparent problem, which I know is not normally present, then a very small adjustment removes the problem.

mak said:

Chris, some of the points you raise I would agree with, but certainly not your remarks about no objective testing of binoculars. I am sure that Leif can explain for himself, but I know that you can evaluate binoculars using a focault test chart (line pairs). How? set up the focault test chart approx at 10m distance and with the binoculars on a sturdy rest. Put several of these charts together (10) and you can evaluate resolution, edge to edge clarity and alignment using these charts.

The theoretical resolution does not say anything about the quality of the optics. Resolution (theoretical) (R(t)) = Only a measure of how much detail (pattern size) that can be resolved theoretically under day light conditions.

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Yes you can evaluate any optical system using a test chart or some other system, but only for the problems that the particular instrument you are testing. It is not wise to make sweeping statements about that model in general, because there will be some that have QC inconsistences. The problems of manufacturing tolerences on optical aberrations dictate that no two binoculars or spotting scopes are identical. Some (of the same model) are close enough to each other to be difficult to seperate on a simple chart test, but could be seperated on a high power star test or by interferometry. Some are easier to seperate because of lack of QC on one of them.
In order to test the resolution of an instrument, you must use a high power, otherwise the resolution threshold can not be seen. This then rules bioculars or low power spotting scopes out. However, you can, as you say, test these instruments on test charts at so many meters distance, but, it will not indicate resolution, it will not indicate what part of the optical system is poorly aligned, which is introducing astigmatism, or whether the eyepiece is adding its own problems or not (unless you can adapt other eyepieces of known quality). So, you can see differences on test charts, but these differences are due to sharpness/contrast, chromatic aberration, astigmatism, LSA etc. not resolution. You are quite right about theoretical resolution not saying anything about the quality of the optics, this was the point I have been unsuccessfully making to Leif. Image sharpness/contrast, presence of aberrations, astigmatism, poor collimation are all entirely seperate from 'resolution'. Resolution is a function of aperture of an optic regardless of whether the optic is diffraction limited, so this makes resolution a theoretical figure for a given aperture. All the other aberrations and manufacturing problems overlie the 'perfect' resolution of an optic, modifying the image to be less sharp, or more colourful, or poorly aligned, or whatever problems it might have. What you see in the image is not lower resolution, but if you like, 'masked' resolution because of the aberrations.
The term resolution is used widely to describe image sharpness, its correct usage is somewhat different, and this is where the confusion lies.
The simple reality is that we can not meaningfully put any mass-produced optical instrument through a simple chart test, and expect all others of the same model to be exactly the same. Each instrument (strictly speaking) must be assessed on its own. If this problem of inconsistency were not true, then the 'Strehl peddling' that occurs in the high end astro refractor market would not occur.

Best regards
Chris

Grousemore said:

Wouldn't it be a pity if these informed discussions on optics are curtailed by personal antagonism? 'Lecturing' often goes down badly in my experience.

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I entirely agree with you. How do you get across a point without backing up that point with an explanation or evidence? It soon descends into 'lecturing'. I don't think it is a detremental thing though, not if meant in the right spirit.
Personal antagonism is also something I am uncomfortable with. I never intend any offence with my original postings, however I find that on sites such as this, there are always those that feel threatened by someone like me, and react in a negative way. This is why I rarely join sites such as this. This is also why very few, if any, opticians in the telescope optics sector of the market take part in these discussions. They soon become targets for one or two of those regular contributors, who like to think of themselves as some sort of 'oracle'.
I do feel a little offended though, when after taking part in a discussion on the 'Scope Survey' thread, I then get a private email through the Birdforum facility from Leif asking me to 'Go Screw Myself'. This then raises questions in my mind about whether this person is genuine or not, and hence modifies my answers to him from then on.


Best regards
Chris

Very fair points,Chris and I hope you continue to contribute your undoubted expertise to BF.
My original Post was an attempt to cool things down,which I hope has worked.

Grousemore said:

Very fair points,Chris and I hope you continue to contribute your undoubted expertise to BF.
My original Post was an attempt to cool things down,which I hope has worked.

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I also hope it has worked.
These types of disputes occur in the astro market discussion sites as well, but usually between manufacturers (cottage industry types), where one questions the honestry/integrity/quality of the other's personality/products, purely as a defensive sales strategy. I have no axe to grind here as I do not retail birding optics (although I used to) , but I care passionately about optics and have made it my business to attempt to learn as much important/fundamental 'stuff' about optics as I can. I have always tried to be truthful about optical instruments, which is why I find myself disliked by some areas of the media and manufacturers, (in the past, a couple of distributors of birding optics and at least one popular monthly magazine). Sometimes, the truth does not sell or promote optics sales, this is unfortunate when sell, sell, sell is the order of our consumer society.

Best regards
Chris

ukbraychris said:

This is also why very few, if any, opticians in the telescope optics sector of the market take part in these discussions. They soon become targets for one or two of those regular contributors, who like to think of themselves as some sort of 'oracle'.

I do feel a little offended though, when after taking part in a discussion on the 'Scope Survey' thread, I then get a private email through the Birdforum facility from Leif asking me to 'Go Screw Myself'. This then raises questions in my mind about whether this person is genuine or not, and hence modifies my answers to him from then on.

Best regards
Chris

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What I told you to "Go screw yourself" that was in response to a private message from you that I found extermely patronising.

In fact I find many of your postings to be patronising. You talk to me (and others?) as if I am stupid. I am not.

In one of your first postings you state that birders do not know what they are talking about when it comes to optics and that their comments should be ignored. How nice. I found that insulting and a sweeping generalisation.

In your latest post you refer to:

"one or two of those regular contributors, who like to think of themselves as some sort of 'oracle'."

I take this to be a snide insult directed at me amogst others. I make no such claims. I contribute in order to pass on what I know and to learn from others. On several occasions when I have stated a falsehood, it has been corrected by Mak, Scampo or whoever. Another poster, a friendly and knowledgeable user called Henry Link, commented in another thread that it is often hard to figure out what binocular manufacturers are doing, and I believe that sharing information in this forum is one way to find out more.

You made a similar remark in an earlier posting where you refer to self styled experts. Was that a snide remark directed at people on this forum? This forum hosts reviews of products including optics written by forum users. It seems that we now know your opinion of these reviews. (I find reviews such as the one of a Zeiss scope to be very useful, including the comments on the optics.)

I posted to this thread a simple statement about how much detail I could see with various binoculars, many of which I have owned. That was the only point I was making, and I stand by what I wrote. You seem to disagree with me. Whether this should be referred to as resolution or sharpness I know not. I am not interested in being lectured at by you or anyone else. Quite why you are going on and on I do not know, but I stopped reading your postings due to the patronising tone and snide remarks.

As I have said, I do not like being talked to as if I am an idiot. I also do not like sarcastic remarks, and snide comments.

If you disagree that the Nikon 8x32 SE shows more detail than a Zeiss 8x30 BGAT, or a Leica 8x32 BN, then I suggest that you carry out some tests, and see what you observe.

Leif said:

If you disagree that the Nikon 8x32 SE shows more detail than a Zeiss 8x30 BGAT, or a Leica 8x32 BN, then I suggest that you carry out some tests, and see what you observe.

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I will not be bullied by Chris Garvey, or anyone else, into saying otherwise. That seems to be what he is trying to do.

Leif said:

I will not be bullied by Chris Garvey, or anyone else, into saying otherwise. That seems to be what he is trying to do.

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Apparently, Grousemore's wish for peace has been ignored. I am not going to illuminate Leif's problems further with a response. It does not deserve one.
Perhaps we should ask a moderator to step in at this point and make a decision. It seems whatever I post, Leif finds it personally patronising. Perhaps a moderator can make decision on whether one of us or both should remain quiet in future.

best regards
Chris

I will make a decision then agree to disagree and move on, locking threads does happen in other threads But a discussion on optics?? Your kidding me!!! Play the Post NOT the poster.

ukbraychris said:

<snip>In order to test the resolution of an instrument, you must use a high power, otherwise the resolution threshold can not be seen. This then rules bioculars or low power spotting scopes out....<snip>... Image sharpness/contrast, presence of aberrations, astigmatism, poor collimation are all entirely seperate from 'resolution'. Resolution is a function of aperture of an optic regardless of whether the optic is diffraction limited, so this makes resolution a theoretical figure for a given aperture. All the other aberrations and manufacturing problems overlie the 'perfect' resolution of an optic, modifying the image to be less sharp, or more colourful, or poorly aligned, or whatever problems it might have. What you see in the image is not lower resolution, but if you like, 'masked' resolution because of the aberrations.
The term resolution is used widely to describe image sharpness, its correct usage is somewhat different, and this is where the confusion lies.<snip>

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Chris,

you are right that "resolution" aka "resolving power" is a well defined scientific entity for the theoretical limit of any optical instrument to produce separable images of two object points (or lines). It can easily be calculated for any optical instrument.

However, as you mention, imperfections in many instruments limit their performances so that this theoretical resolution is not met in practice. However, it is not wrong to still use the term "resolution" for the real ability "to produce separable images of two object points" of an imperfect instrument. In fact, "resolution" is used in that way, also within science, to describe the performance - the "'masked' resolution" - of different imperfect instruments (i.e., not reaching the diffraction limit).

Therefore, we can talk about resolution regarding binoculars and spotting scopes in terms of what you can measure from resolution charts. This is not wrong and IMO more appropriate in a forum for birders who has to use such imperfect binoculars and spotting scopes due to practical, technical, and economical reasons.

Regards, Jens.

There is obviously a number of posters who have considerable optical knowledge (I am sure that birders are highly regarded by manufacturers as having some optical knowledge or someone who can make a valid point, that is why they listen) but maybe we can all become over technical.

Sure some people have measured data at their disposal ( lab results and not subjective) to debate the subject.

With respect to all, sometimes it is beneficial to "keep it simple" so that the majority of viewers can take away useful information, which will be more beneficial than over elaborate technical talk.

Jens in his last paragraph makes a valid point.

jebir said:

Chris,

you are right that "resolution" aka "resolving power" is a well defined scientific entity for the theoretical limit of any optical instrument to produce separable images of two object points (or lines). It can easily be calculated for any optical instrument.

However, as you mention, imperfections in many instruments limit their performances so that this theoretical resolution is not met in practice. However, it is not wrong to still use the term "resolution" for the real ability "to produce separable images of two object points" of an imperfect instrument. In fact, "resolution" is used in that way, also within science, to describe the performance - the "'masked' resolution" - of different imperfect instruments (i.e., not reaching the diffraction limit).

Therefore, we can talk about resolution regarding binoculars and spotting scopes in terms of what you can measure from resolution charts. This is not wrong and IMO more appropriate in a forum for birders who has to use such imperfect binoculars and spotting scopes due to practical, technical, and economical reasons.

Regards, Jens.

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Jens

OK, as long as we can agree terms, then that is half the battle. If we want to use the term 'resolution' to mean the final image quality of an instrument as a result of a combination of optical imperfections, that can be tested at any fixed magnification on extended detail, then we can adopt the term 'resolution' to mean that, but we must agree terms, and the problem is that 'resolution' means different things to different people. Given that extended detail is overlapping diffraction patterns from millions of Airy discs making up a two-dimensional surface of detail, as opposed to a single Airy disc and diffraction rings of a point source, then both are connected. Hence any aberration which is larger than an Airy disc can be seen on one Airy disc or the effect of such on many Airy discs in extended detail. A general agreement that this means 'resolution' instead of 'resolving power' is fine as long as a group agrees and understands the differences. Problem is, how do you include other problems such as, for example, internal reflections. Perfect lenses can transmit reflected light to the focal plane. Light from cell walls, prism housings, field stops, eyepiece coatings, which then modifies the final image by lowering contrast, hence making some fine detail more difficult to see. Fine detail on the edge of visibility then becomes invisible. Can we call this a drop in resolution? This is having no effect on LSA, LCA, coma, astigmatism, resolving power, but yet is reducing the visibility of fine detail. An optician would not regard this as a meaningful part of the image as it is scattered unfocussed light on the focal plane. An astronomer or birder would consider this an important part of the image because it is formed by a part of the instrument. An astronomer would recognize this effect and look to baffle the offending section of the instrument. I am not sure the average birder would know how to solve this problem, or even be able to because of sealed instruments. Nevertheless, it is assessed with this problem and given a rating accordingly. If you want to include the effect of internal reflections as part of the 'resolution' modifying aspect of an optic, then again, this must be stated and terms agreed. This is one of the problems with discussing optics on an open forum, some use terms loosely, others not. A group of opticians talk the same language, astronomers a different one, birders a different one still. Optics is one of those subjects where mind reading is advantageous. Can you see what that person is seeing, do you understand the meaning of what that person is explaining, and do you understand it in the same way that this person understands it. How difficult is it for an entire market to agree meaning and terminology with another entire market. All you can do is stick to fundamental laws and rules, using them when appropriate, to help the observer understand what it is they are seeing.
Best regards
Chris

Folks,

Let's try to have some peace here for the sake of ALL BF members. It may be worthwhile to remember that at their peaks, all great civilizations of the world tolerated diverse views and dealt with disagreements as gentlemen. The Dark Ages and the fall of knowledge (of arts, sciences, literature, music, etc) was a direct result of intolerance and the people's inability to deal with disagreements. Fortunately, the Arab world, at the time extremely tolerant of diversity, kept this knowledge alive.

Let's try to tolerate and respect everyone's knowledge so that all members may benefit from several points of view and come to their own conclusions about truth. This would ensure that BF does not fall into a period of Darkness...

...IMO.

ukbraychris said:

There are too many inconsistencies in mass-produced optics to test a low power instrument on some chart at a distance, and then assume that all other binoculars of the same model will be identical, and then announce that model A is better than model B. Certainly a low power binocular or spotting scope can not be tested for resolution on a chart. If you know the aperture you know the resolution threshold. A chart may show imperfections in the design, aberrations etc for that one particular binocular, but don't confuse this with resolution differences.

Best regards
Chris

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If you really mean this, then it is meaningless to discuss binoculars and to read tests. If some says Leica Ultravid 8x42 gives a better view than Leica BN 8x42 i must remember he is talking about one specific binocular?
Of course not all binoculars are exactly like,but there are of course less differences in quality in a Ultravid than in low cost binocular. So i feel it is not incorrect to talk about models generally. Why else do we buy expensive binocular models if not the quality is the reason?

Basically, I think most things have been said that need to be said in this thread. However, IMO the reason for the fiery debate here is the different meaning that different individuals lay in the word "resolution" and how we succeed in communicating this to each other.

ukbraychris said:

OK, as long as we can agree terms, then that is half the battle. If we want to use the term 'resolution' to mean the final image quality of an instrument as a result of a combination of optical imperfections, that can be tested at any fixed magnification on extended detail, then we can adopt the term 'resolution' to mean that, but we must agree terms, and the problem is that 'resolution' means different things to different people.

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An optician or an astronomer who is building his own telescopes may think of the resolution in terms of the theoretical limit. However, I don't think I am wrong when I state that most professional consumers of optical instruments, e.g., photographers, optical microscopists, electron microscopists, and some times even astronomers(!), mean by "resolution" the ability of a given optical instrument to produce separable images of two object points or lines. The instrument is then seen as a black box and the manufacturers just provide the number characterizing the actual performance: resolution=separation between separable points or lines (of course - there are additional quality mesures). Who cares if the real "resolution" is limited due to one or the other reason if one can't do anything about it anyway?

Unfortunately, producers of birding optics do not provide any measures of the optical quality of their products. Therefore birders trust their own eyes when judging the image quality of a given instrument and it is natural to talk about the amount of detail that can be seen as the "resolution" just as when talking about camera lenses or other instruments. It would certainly be helpful to discuss birding optics if we could have some measure of what kind of detail our gear is capable of. After a while, we could use the numbers like we use horespower and torque when judging a car engine.

My point is that it isn't wrong saying that one can see a difference in the "resolution" between two instruments even if it isn't the diffraction limited resolution that is seen.

A group of opticians talk the same language, astronomers a different one, birders a different one still. Optics is one of those subjects where mind reading is advantageous. Can you see what that person is seeing, do you understand the meaning of what that person is explaining, and do you understand it in the same way that this person understands it. How difficult is it for an entire market to agree meaning and terminology with another entire market. All you can do is stick to fundamental laws and rules, using them when appropriate, to help the observer understand what it is they are seeing.

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Right, communicating only with written text in English (which for many aren't their mother toungue) certainly pose high demands on our abilities to communicate. Here we are a bunch of birders being opticians, physicists, plumbers, nurses, etc. trying to figure out how our binoculars and scopes work. IMHO, it is therefore not always useful to use fundamental laws and rules - simply because it is a language that isn't always understood.

I think we are (I am) quite off topic so I will not talk about semantics and communications anymore.

Cheers, Jens.