Ocular Lens Size (3 Viewers)

[ArchStanton]

I understand and accept 'the science' behind the so-called 'eyebox', it makes perfect sense. However, I have never really fathomed out why some binoculars have a reputation for being particularly finicky or unfriendly, and others of the same objective/magnification formula (8x42, for example), or even an entire model line at the various magnifications in the range, do not. The knowledgeable ones will usually maintain that it is the operator of the binocular which is the problem, not the binocular itself, insisting that it is simply a matter of setting up the binocular correctly. However, those same people also maintain that it is important to try before you buy, to make sure the binocular fits (or works for) you, eye relief and IPD allowing.

I get the theory, I don't really understand why the reality appears to be somewhat different.

I have experience of a pretty broad range of binoculars, and some I'm able to just pick up and use without thinking about them, others (despite adequate eye relief and IPD range) I simply can't, no matter how hard I try (including ages spent fiddling around with o-rings). This really doesn't bother me, apart from the fact that it goes against 'the science'.

I’ve tried quite a few binoculars priced between $400-1000 in my quest for a new pair of roof prism binoculars for birding. I’ve settled on the Opticron Oregon 8x42’s because as you said “I’m able to just pick them up and use without thinking about them.” I purchased a pair of Zeiss Conquest HD 8x32’s at 40% off and really wanted to keep them, but they just didn’t provide a comfortable view for me. I can quickly put Oregons up to my eyes and easily find the birds I’ve spotted without fiddling with the binoculars. IMHO binoculars are like comfortable shoes that may fit your feet but not someone else.

 

[tenex]

"Eye box" -how deep the eye is in the arch and what shape it has... its depends on the physiognomic architecture of each person.

That's more a matter of how deep an eyecup each individual will require to deal with the eye relief of a particular bin. I'm not sure there's an agreed-upon definition of ER, but it's probably the distance to the center of the eye box, whereas the finicky quality here has to do with the size (extent) of the eye box itself, and issues like spherical aberration of the exit pupil, all of which depend on details of the optical design of the eyepiece.

The knowledgeable ones will usually maintain that it is the operator of the binocular which is the problem, not the binocular itself, insisting that it is simply a matter of setting up the binocular correctly.

This is a bit like my usual suggestion that most people who think they can't hold 10x steady enough really could if they practiced more. That's probably true, but the fact remains that 10x is more of a challenge than 8, and it becomes a personal question of how much trouble one is willing to go to. Henry Link comes to mind as someone here who has found eye positioning with NL 8x42 tricky, but worth learning to deal with. Other models are well known and liked for their greater ease of use, but obviously NLs can be used or they wouldn't sell at all.

 

[Maljunulo]

This is a bit like my usual suggestion that most people who think they can't hold 10x steady enough really could if they practiced more.

I agree with this.

After most of a lifetime of looking through binoculars, it wasn’t until I began to feel my age hat I switched from 10X42 to 8X32.

It was time.

 

[Hermann]

This is a bit like my usual suggestion that most people who think they can't hold 10x steady enough really could if they practiced more. That's probably true, but the fact remains that 10x is more of a challenge than 8, and it becomes a personal question of how much trouble one is willing to go to.

No matter how steady you think you can hold a 10x binocular you still lose a considerable amount of resolution. According to Vukobratovich (1989, quoted e.g. in Merlitz 2023:149-150) the efficiency of a 10x binocular is 0.67, in other words you lose about 33% of the resolution compared to a mounted 10x. (BTW, this figure seems me to be on the low side, other researchers (e.g. Brunnckow et al. 1944; Hohmann/Nolting 2002) found higher losses of more than 40%.) This is mainly due to what's called "physiological tremor" and can't really be avoided unless you take certain drugs such as alcohol ... 😁

In addition to that, many people put some conscious effort into reducing the shake of their binoculars, leading to faster fatigue, especially if you use your binoculars for extended periods of time, e.g. on a migration watch.

The only way around this problem is the use of stabilized binoculars or some sort of support.

Hermann

 

[Elkhornsun]

The exit pupil diameter is probably what you are dealing with and this is a function primarily of the diameter of the objectives and the amount of magnification. A 7x bino is going to provide a larger exit pupil diameter than a 12x with the same diameter objective.

 

[tenex]

No matter how steady you think you can hold a 10x binocular you still lose a considerable amount of resolution. According to Vukobratovich (1989, quoted e.g. in Merlitz 2023:149-150) the efficiency of a 10x binocular is 0.67, in other words you lose about 33% of the resolution compared to a mounted 10x. (BTW, this figure seems me to be on the low side, other researchers (e.g. Brunnckow et al. 1944; Hohmann/Nolting 2002) found higher losses of more than 40%.) This is mainly due to what's called "physiological tremor" and can't really be avoided unless you take certain drugs such as alcohol ...

This argument, which appears repeatedly on the forum, suffers from certain obvious problems which include:
(1) Handheld binoculars all lose efficiency. By the approximation you've used from Vukobratovich, the resolution loss would still be 29% at 8x, and 26% even at 7x, figures that sound hardly less worrisome than 33% and do not constitute a strong argument against 10x.
(2) Empirical formulas like this one are confirmed by averages of relatively small samples of test subjects whose experience was not specified, while the extent of variation in the general population remains unknown.
(3) Vision is a complex process also involving how well the brain learns to compensate for a shaking image, not just the amount of shaking itself.
(4) Resolution is not the only parameter involved in detail recognition on distant objects, magnification itself matters also.
(5) Naturalists are not attempting to read test charts in the field.

 

[WJC]

I understand and accept 'the science' behind the so-called 'eyebox', it makes perfect sense. However, I have never really fathomed out why some binoculars have a reputation for being particularly finicky or unfriendly, and others of the same objective/magnification formula (8x42, for example), or even an entire model line at the various magnifications in the range, do not. The knowledgeable ones will usually maintain that it is the operator of the binocular which is the problem, not the binocular itself, insisting that it is simply a matter of setting up the binocular correctly. However, those same people also maintain that it is important to try before you buy, to make sure the binocular fits (or works for) you, eye relief and IPD allowing.

I get the theory, I don't really understand why the reality appears to be somewhat different.

I have experience of a pretty broad range of binoculars, and some I'm able to just pick up and use without thinking about them, others (despite adequate eye relief and IPD range) I simply can't, no matter how hard I try (including ages spent fiddling around with o-rings). This really doesn't bother me, apart from the fact that it goes against 'the science'.

Mark Twain asked his publisher, William Dean Howells, why there was so much garbage in print, his response:

"Because paper never shuns ink!"

 

[Canip]

Empirical formulas like this one are confirmed by averages of relatively small samples of test subjects

You would habe to disclose the source of this information to make it credible for me. Are you saying this is usually the case, or it is the case in the particular instance? I happen to believe that there have been large documented studies on this subject of binocular and scope efficiency.

 

[Swedpat]

No matter how steady you think you can hold a 10x binocular you still lose a considerable amount of resolution. According to Vukobratovich (1989, quoted e.g. in Merlitz 2023:149-150) the efficiency of a 10x binocular is 0.67, in other words you lose about 33% of the resolution compared to a mounted 10x. (BTW, this figure seems me to be on the low side, other researchers (e.g. Brunnckow et al. 1944; Hohmann/Nolting 2002) found higher losses of more than 40%.) This is mainly due to what's called "physiological tremor" and can't really be avoided unless you take certain drugs such as alcohol ... 😁

In addition to that, many people put some conscious effort into reducing the shake of their binoculars, leading to faster fatigue, especially if you use your binoculars for extended periods of time, e.g. on a migration watch.

The only way around this problem is the use of stabilized binoculars or some sort of support.

Hermann

This is still very individual. Using binoculars has a similarity to shooting.
You can train stability like a shooter does.
But it's true that freehand can never be as stable as mounted or image stabilization.
My experience is that even with 5x a support can provide the crucial stability to see details that are close to being seen freehand.

 

[Ignatius]

Discounting any further discusssion on sample size, validity of studies etc., I would just like to agree with ArchStanton's observation (#21). Going by all that has been said in this thread, my personal best eye box ist that of the FL T* 7x42. It is the only bino I have which I can just pull up, stick in my eye sockets and enjoy the view. No fiddling, no jiggling around, no trying to find the perfect spot to rest the eye cups on/under the brow. It just fits. I have others which come close, but that one bino is IT. From the discussion here I also infer, that this wonderful experience will not necessarily be repeated should I purchase it's smaller sibling, the FL 8x32. Which would be a terrible shame as it appears to have so much going for it.
Also: one thing I found very interesting in that Vukobratovich paper was this "Schober et al. also determined that the size and weight of the binocular did not affect tremble frequencies." ie. it makes no difference whether one uses a big, heavy 10x56 or a svelte and light 10x25 in daylight conditions - the efficiency loss due to one's physiological tremor is the same. So much for the theory that a heavier bino is easier to hold steady

 

[Canip]

This may now sound pedantic, but:
Your quote clearly refers to tremble frequencies, not the amount of shake or the amplitude of the respective movement. But perhaps I read too much into that paper?

 

[Maljunulo]

One man’s pedantry is another man’s precision of expression.

Words have meanings, and if they are not used correctly all is chaos and misunderstanding.

(especially when we are being “scientific”)

 

[Hermann]

This argument, which appears repeatedly on the forum, suffers from certain obvious problems which include:
(1) Handheld binoculars all lose efficiency. By the approximation you've used from Vukobratovich, the resolution loss would still be 29% at 8x, and 26% even at 7x, figures that sound hardly less worrisome than 33% and do not constitute a strong argument against 10x.

IMO his figures are too optimistic. Anyway, I did not argue against using 10x binoculars per se. I merely pointed out that you do lose resolution, and the higher the magnification, the more you lose. Put different binoculars on a tripod and check how much resolution you gain compared to handholding them.

(2) Empirical formulas like this one are confirmed by averages of relatively small samples of test subjects whose experience was not specified, while the extent of variation in the general population remains unknown.

Any references? BTW, an interesting question is how large a sample needs to be for the results to be valid. I also don't think you need to study the "variation in the general population". The physiological tremor - the main reason for hand shake - has been studied in some detail, and it affects everyone.

(3) Vision is a complex process also involving how well the brain learns to compensate for a shaking image, not just the amount of shaking itself.

True.

(4) Resolution is not the only parameter involved in detail recognition on distant objects, magnification itself matters also.

Of course it does. But you wouldn't use, say, a 20x50, handheld to get more detail on a bird? What's a sensible limit for handheld use? 12x? 15x? At what point do you lose so much resolution due to shake that you'd be better off with a binocular with lower magnification?

(5) Naturalists are not attempting to read test charts in the field.

No. But they're trying to see tiny field marks on birds. That's a lot more demanding than reading test charts.

Hermann

 

[dorubird]

I don't know what the mathematical numerical resolution ratios are between 8x and 10x binos, but my practical experience with top binoculars shows that, with 10x bino I read very far away inscriptions much easier than with a 7x and a little easier than 8x bino. Even if I stabilize much better 7x binos (almost motionless), my technique with 10x binos is quite good (small movements) so that the difference in magnification gives me some details to read more easily. The 8x binoculars are closer to 7x in terms of stabilization, and quite close to 10x in terms of details easy to read handheld, but still slightly under 10x . But if they are handheld for long periods, 7x bino is the most relaxing of the three, and 10x the most tiring, which is an important thing!

 

[tenex]

You would habe to disclose the source of this information to make it credible for me. Are you saying this is usually the case, or it is the case in the particular instance? I happen to believe that there have been large documented studies on this subject of binocular and scope efficiency.

I looked into this subject several years ago during a discussion here, and specifically recall a study of this sort whose sample size struck me as quite small and poorly characterized, but am not finding it at the moment. I could hope that it was actually the paper (Marriott 1972) cited in Vukobratovich's note 6, but possibly not. I too would believe that there have been larger studies (even that Marriott's was one) if you had this information and disclosed it. Or perhaps someone else could step in... Holger? This discussion would go better with an expert on hand. Or maybe it isn't worth it, since we don't all even seem to be talking about the same thing...

IMO his figures are too optimistic. Anyway, I did not argue against using 10x binoculars per se.

And yet using 10x bins was the topic here. What you have instead is an argument for using a tripod (or IS bins as I recall), as remarkably few do, which has sidetracked the discussion. The subject of resolution loss handheld vs mounted has little relevance to choosing 7/8x vs 10x, because that difference is quite small -- which is why I'm surprised how many people here say they can hold 8x but not 10, which is the largest seller overall.

BTW, an interesting question is how large a sample needs to be for the results to be valid.

I'm actually quite satisfied with even a small sample size for confirming that the approximation involved is on the right track. My point was that it doesn't give a good enough idea of the range of individual variation.

I also don't think you need to study the "variation in the general population". The physiological tremor - the main reason for hand shake - has been studied in some detail, and it affects everyone.

The question is how much it affects the ability of different individuals to extract detail. You really seem not to be tracking what I'm talking about, and so to be talking very much at cross purposes.

But you wouldn't use, say, a 20x50, handheld to get more detail on a bird? What's a sensible limit for handheld use? 12x? 15x? At what point do you lose so much resolution due to shake that you'd be better off with a binocular with lower magnification?

I've actually never tried 20x, but gladly use a 15x56 to see more detail on distant enough birds in open country. That may be somewhat rare, but a more significant number of people use 12x50 for raptors or other purposes. Your or someone else's answer might be different, so one really has to ask. It's not a question you get to settle once and for all with some simple statement about physiological tremor.

 

[Ignatius]

This may now sound pedantic, but:
Your quote clearly refers to tremble frequencies, not the amount of shake or the amplitude of the respective movement. But perhaps I read too much into that paper?

Of course you are correct. I was too cursory. And it is indeed probably also correct that a heavy binocular will attentuate the amplitude of the movement more than a leightweight one.

 

[Binastro]

It depends what one is looking at and whether day or night.

I have found a 10% increase in actual resolution with a 1x magnification by resting my head against a lamp post.

It depends how tired one is, both generally and arm muscles.

It varies from binocular to binocular.

I had no trouble at night using a very good Japanese 20x80, best of three to view the sky.
But one is looking up at say 45 degrees and this is much more stable than holding the binocular horizontal.
I could freehold with no support for twenty minutes.
However, others could not.
Looking at comet Halley, all of the party of about 15 agreed the best view was with the 20x80 compared to different binoculars and a good 6 inch Newtonian.
The 20x80 weighs about 2.5 kg and definitely does not move as much as a light binocular.

I generally used 10x50, 12x45 or 12x50 and had no trouble hand holding.
Sometimes I might rest the binocular against a tree.

With the 20x60 I needed support, a car roof, wall or similar.

As to the actual percentage increase in resolution, I think the Canon 8x25 IS has double the actual resolution of a non stabilised 8x binocular.

The scientific tests are optimised for best results, I presume.
This is not the real world.

With the Canon 18x50 IS the gain is about 3x compared to the binocular with IS off.

It also depends whether one is panning, say following an aircraft, or trying to hold still. Panning with a IS binocular is often very good.

Also test charts are again not a good test, as you are looking at a known object.
It is an unknown object that is revealed with IS binoculars compared with a non IS binocular, where the object is not even suspected.

With the Canon 8x25 IS I looked at an aircraft and saw little but an aircraft.
As soon as I switched the IS on I saw ETIHAD, I think, on the side and a yellow colour, which may actually have been gold.
With IS off I did not even suspect writing on the fuselage.

For bird watching, maybe for hours, I don't know how much loss there is hand holding.

Regards,
B.

 

[tenex]

As soon as I switched the IS on I saw ETIHAD, I think, on the side...

"Etihad Airways is one of two flag carriers of the United Arab Emirates... the second-largest airline in the UAE after Emirates. The name Etihad is the Arabic word for 'Union'." - Wikipedia

I wonder what your 18x50 would have shown, with IS off.

 

[Gumball]

While this topic has been discussed across BF and CN, after a brief search I wasn’t able to find a clear answer to my question re ocular lens size. I am hoping members will be able to confirm my current understanding or correct me.

A larger diameter ocular lens will have a more forgiving eye box and longer eye relief.

Is this a fair assumption?

Why is this spec reported?

Thank you

I am not an Optical Physicist. I have several binoculars with ocular sizes ranging from about 8mm to 23mm.
Using a variety of these in widely varying circumstances, the larger the diameter of the ocular lens, more comfortable to "hand-hold", and make for much easier viewing.

 

[Patudo]

(4) Resolution is not the only parameter involved in detail recognition on distant objects, magnification itself matters also.

This squares with my own experience. Sometimes you can extract more info from a larger but shakier image; and binoculars can be steadied quite significantly by bracing your elbows on something solid, etc. I find 15x too shaky (and field of view too small) for my birding, but I do use a 12x50B in preference to 10x when my targets are at great distance.