Diopter Adjustment (1 Viewer)

[lmans66]

A lovely day birding today..... I just came out of the woods upon a clearing and there was a nice looking bluebird perched with a worm. I viewed it with my bins and determined that it wasn't as clear as I thought. I wonder if being in the woods or early morning before you wake up or when your eyes are tired at other times, that your diopter needs to be tweaked, which I did, or...I wonder if my diopter was just wrong to begin with all-told. Thoughts on this ?

 

[Pinewood]

Hello Imans66,

Yes, the dioptre setting might have to be changed because your vision may change during the day. A fine adjustment of the setting might have to be made when you move from a close target to a distant target. If I recall correctly Leica suggests that you set the dioptre when focussing on something in the near distance, maybe ten metres, which would be a compromise.

Stay safe,
Arthur

 

[eitanaltman]

A lovely day birding today..... I just came out of the woods upon a clearing and there was a nice looking bluebird perched with a worm. I viewed it with my bins and determined that it wasn't as clear as I thought. I wonder if being in the woods or early morning before you wake up or when your eyes are tired at other times, that your diopter needs to be tweaked, which I did, or...I wonder if my diopter was just wrong to begin with all-told. Thoughts on this ?

I frequently experience this birding in the early morning, which I ascribe to "tired eyes". Haven't cleared all the cobwebs out.... sometimes the first few times I look through the bins on an early morning walk it doesn't feel as "sharp" as normal, leading me to muse if something is wrong with the focus or diopter, but eventually I realize it was probably just my eyes.

Secondarily, depending on the exit pupil of the bins, in mediocre light things can get less "comfortable" to view as your own pupils dilate. Sometimes in the early morning or dusk you don't realize how poor the light is, because your eyes/brain are so capable of compensating. But if you're using an 8x32 with a 4mm exit pupil, you become quite aware of it when you put your bins up to your eyes and it's tougher than normal to get a bright, sharp image.

 

[PeterPS]

A lovely day birding today..... I just came out of the woods upon a clearing and there was a nice looking bluebird perched with a worm. I viewed it with my bins and determined that it wasn't as clear as I thought. I wonder if being in the woods or early morning before you wake up or when your eyes are tired at other times, that your diopter needs to be tweaked, which I did, or...I wonder if my diopter was just wrong to begin with all-told. Thoughts on this ?

Besides "tired eyes" the other possibility is that you might have a pair of binos with a drifting diopter. Even alpha binos might suffer from the latter problem, such as the first-generation EDGs.

 

[lmans66]

I am going to experiment a bit....just see if my eyes tire, differ depending on morning or whatever. The bins are fine, ....just my eyes I suppose as one ages....

 

[WJC]

A lovely day birding today..... I just came out of the woods upon a clearing and there was a nice looking bluebird perched with a worm. I viewed it with my bins and determined that it wasn't as clear as I thought. I wonder if being in the woods or early morning before you wake up or when your eyes are tired at other times, that your diopter needs to be tweaked, which I did, or...I wonder if my diopter was just wrong to begin with all-told. Thoughts on this ?

Attached is a snippet from a draft I submitted this morning to the cruiser's Latitudes & Attitudes magazine. Although important to achieving a precise/fiddle-free focus, I'll bet no one has seen it in print, before.:cat:

Bill

 

[bbbird]

This is really wonderful information. I came here to see if anyone else found that they had to tweak their diopter from time to time. I thought maybe there was something wrong with me or my binoculars.

Thank you WJC for those snippets. If I understand correctly, the idea is to pick a stationary object in mid distance (say, a tree across the street or something like that) and stare at a spot on it for a while, then bring the bins up and focus on the same spot. Perhaps performing the diopter adjustment while going back and forth between the bins and the naked eye staring spot. The act of staring enables you to short circuit your brain's wanting to constantly change the eye's focus so that you can then fix a baseline diopter setting.
Is this all about right?
Again, thanks everyone for sharing your knowledge and experience.

 

[18000bph]

One strange thing I have noticed occasionally while setting the diopter on some binoculars:

I focus the binocular with my left eye. Then adjust the diopter for the right. When I then look at the same object with both eyes I sometimes need to refocus the binocular by a small amount even though each eye individually appears perfectly focused.

This doesn't ever happen if I set the diopter while focused at infinity, so I have developed the habit of doing just that. However based on the methods presented in this thread, it sounds like I have been doing it wrong. I guess I should get all the binoculars out for adjustment! My diopter adjustment tends to end up within a sliver of "0" unless the binocular is off center, so I don't think it matters that much for me.

 

[WJC]

This is really wonderful information. I came here to see if anyone else found that they had to tweak their diopter from time to time. I thought maybe there was something wrong with me or my binoculars.

Thank you WJC for those snippets. If I understand correctly, the idea is to pick a stationary object in mid distance (say, a tree across the street or something like that) and stare at a spot on it for a while, then bring the bins up and focus on the same spot. Perhaps performing the diopter adjustment while going back and forth between the bins and the naked eye staring spot. The act of staring enables you to short circuit your brain's wanting to constantly change the eye's focus so that you can then fix a baseline diopter setting.
Is this all about right?
Again, thanks everyone for sharing your knowledge and experience.

bbbird

Thank you.

Everyone “tweaks their diopter from time.” My purpose was to cut that time by showing how it CAN be cut. And many, many people think there is something wrong with their eyes. More often than not it is their eyes, but nothing is WRONG; they just don’t understand their physiological realities.

“Mid-distance”? Nope. It shouldn’t be too close. But any distance from mid-distance to infinity will work. But the way, you are portraying STARING is counterproductive. You seem to be forcing the focus. In the immortal words of Aristotle, “That’s a no-no!” Just try not to focus on anything. If you can do that, you’re on your way to a better observing experience. But yes, you want to “short circuit” your brain’s involuntary input.

With a little tweaking of your thinking, you are correct. And I must admit, for those who have never encountered this concept, the whole thing can seem nebulous. With practice, it will become apparent.

Because of spending 50 years performing the task and writing about it, I can almost perform binocular collimation in my sleep. It’s a VERY simple operation for those who understand that “simple operation.” However, 100% of the “collimation tips” currently on the Internet are WRONG. And some offer page after page after page of confusing mathematical gyrations that lead to conditional alignment, at best.

18000bph

Although there may be no numerals on the left EP, it’s still a diopter adjustment, and learning to stare can help eliminate the problem. It may not come easy ... but it will come.

So many people like to brag about leaving their diopter setting at “0.” If their natural dioptric setting is close to “0,” this might work ... for a while. If their natural dioptric setting is a few diopters distant, the focus will lead to a strained view.

It should be remembered that there is no such thing as a non-electronic auto-focus binocular and for the most precise focus—considering depth of focus—the binocular’s focus must be used.

Finally, don’t over-think this; it was meant to help. If you have to think too much about this, the purpose is thwarted. Consider it; occasionally try it. If it gets to be a chore, it’s of no value. :cat:

Cheers and Blessings,

Bill

 

[Omid]

Hi Bill,

Nice information! thank you for posting about your experience. Your observations (coming from years of experience and talking to actual users) are consistent with my theoretical study of visual ergonomics of binoculars. You can see a few posts which address focusing in my topic New Horizons II. These posts are just the tip of a huge iceberg..

Focusing the binoculars is a very important (and mainly neglected) subject which has a profound effect on the quality of the observation. Part of the problem are the binoculars themselves (they give the eye conflicting and un-natural visual stimuli with regards to focus and parallax). There are also several physiological and Psychological factors that affect focusing. For example, the user (even if he is young and healthy with a full-14 diopter focusing capability) tends to over-focus when looking through a visual instrument. (This is because, the brain thinks the image is located inside the actual physical body of the instrument).

The above phenomenon is called "instrument myopia" and there are many scientific studies that confirm it. I have attached a particularly interesting study conducted by the US Army scientists.

Best regards,
-Omid

PS. Bill, you might want to correct one sentence on page two of your article. It says that depth of field increases with "magnification" while in reality depth of field of binoculars decreases with magnification.

 

[Patudo]

Eitan's experience above mirrors mine. There can be a difficult period before sunrise (much shorter in sunny San Diego than in the UK, I'll warrant) where even an excellent 8x32 can seem fiddly - especially so if you have spent the whole working week at your desk away from the binoculars. On a bright clear morning it passes quickly; but when an overcast morning is forecast, I prefer my 8x42, which is much easier on the eye.

Tweaking the diopter is a bit of a different issue. I find when I'm using longer eye relief binoculars, which enable me to wear my glasses, it's rarely necessary to tweak the diopter, except maybe on a binocular I haven't used for some time (PeterPS is quite correct that some binoculars have a wandering diopter). Short eye relief binoculars which need to be used straight to the eye are different. I do need to tweak the diopter from time to time over a long session when using these - more often, it seems, in summer when there are more issues with pollen and pollution. It's just as well that the diopter on these is on the right eyepiece and easy to adjust.

I focus the binocular with my left eye. Then adjust the diopter for the right. When I then look at the same object with both eyes I sometimes need to refocus the binocular by a small amount even though each eye individually appears perfectly focused.

The same happens, or used to happen with me - I often had to turn back the focus very slightly after getting my right eye dead sharp. Of late, what appears to be astigmatism in my right eye has made it quite tricky to get the right barrel dead sharp, and I've found the best results have been achieved by tweaking the diopter with both eyes open, making very slight adjustments until the best image is achieved. I enjoy using my old porros enough to still continue to use them, but can imagine a day will come when my vision has deteriorated enough that these binoculars can no longer deliver the image quality I need. I'll have to sell them then.

 

[WJC]

Hi Bill,

Nice information! thank you for posting about your experience. Your observations (coming from years of experience and talking to actual users) are consistent with my theoretical study of visual ergonomics of binoculars. You can see a few posts which address focusing in my topic New Horizons II. These posts are just the tip of a huge iceberg..

Focusing the binoculars is a very important (and mainly neglected) subject which has a profound effect on the quality of the observation. Part of the problem are the binoculars themselves (they give the eye conflicting and un-natural visual stimuli with regards to focus and parallax). There are also several physiological and Psychological factors that affect focusing. For example, the user (even if he is young and healthy with a full-14 diopter focusing capability) tends to over-focus when looking through a visual instrument. (This is because, the brain thinks the image is located inside the actual physical body of the instrument).

The above phenomenon is called "instrument myopia" and there are many scientific studies that confirm it. I have attached a particularly interesting study conducted by the US Army scientists.

Best regards,
-Omid

PS. Bill, you might want to correct one sentence on page two of your article. It says that depth of field increases with "magnification" while in reality depth of field of binoculars decreases with magnification.

PS. Bill, you might want to correct one sentence on page two of your article. It says that depth of field increases with "magnification" while in reality depth of field of binoculars decreases with magnification.

Dear Opto-Geek,

You need not be kind and politically correct with me. That could have been handled nicely with:

“Look, stupid, you got that completely BACKWARDS.” I am a stickler for opto-accuracy, so I would have deserved it! I don’t know what I was thinking but I remember that time back in ’58 when I made a mistake. But, hey, cut me some slack ... I was only seven!

Thanks for bringing that to my attention. I have corrected the submitted article that I might not be an idiot on a much larger scale. When I finish this memo, I will replace the article on BF.

Now, in an effort to make amends for my carelessness, I will offer another piece of information.

Some people use “parallax” and “collimation” interchangeably. I can see the reason for doing so, but:

PARALLAX is an observed CONDITION.
COLLIMATION is a CORRECTIVE measure.

Errors in collimation are noticed in binoculars when images from the two telescopes don’t coincide and the observer sees an imprecise or double image.

Errors in parallax are noticed when the focus of the objective and the EP don’t coincide. No double image is produced here. But in rifle sights, telescopic alidades, or other similar instruments the reticle or crosshair will move relative to the target when, in the absence of parallax, the center of the reticle or crosshair will remain fixed on a precise point on the target ... as it should be. :cat:

 

[WJC]

It appears I am too late to edit or delete it, so here in the whole thing, again.
**********************

Attached is a snippet from a draft I submitted this morning to the cruiser's Latitudes & Attitudes magazine. Although important to achieving a precise/fiddle-free focus, I'll bet no one has seen it in print, before.

 

[Stephen Prower]

WJC

Many thanks for the article! I have read and been instructed by your very useful recommendation of 'staring' before. You explain the reasons for the recommendation with exceptional clarity.


Imans66

The diopter adjuster of my Opticron 8x32 SR.GA is easily nudged out of position.

If it helps I attach a photo of a mod that I have done so that I can check instantly in the field, without needing to fiddle about with reading glasses, that the adjuster is set correctly.

[Also you will see that, to habituate me to placing my thumb on the binocular clear of the adjuster ring, I have stuck a suitably positioned piece of velcro on the right hand prism cover.]


Stephen


I explain briefly why, for the time being, I choose to live with a faulty adjuster.

I shall just say that the story starts when I reported the fault to Opticron for repair under warranty. They refused to acknowledge it to be a fault.

A set screw that is frozen in position stops me from getting into the adjuster to re-lubricate it.

I haven't yet got round to seeking out a suitable O-ring to freeze the adjuster in position. Bicycle inner tube and similar fixes have provoked mechanical warning off signs

 

[tenex]

...Part of the problem are the binoculars themselves (they give the eye conflicting and un-natural visual stimuli with regards to focus and parallax).... This is because, the brain thinks the image is located inside the actual physical body of the instrument. The above phenomenon is called "instrument myopia"...

It's not obvious to me that what you've said on the subject in the referenced (sporadic, disjointed) thread agrees with what Bill writes here. Formulas have been cited whose relevance is unclear. You talk about virtual images, others don't. Even the details vary; you've stated that relaxed viewing occurs at a focus distance of around 1m, while other sources say around 6m (optical infinity) which also seems to be what Bill is suggesting by "staring". I'd be glad to have this issue coherently resolved.

 

[Omid]

It's not obvious to me that what you've said on the subject in the referenced (sporadic, disjointed) thread agrees with what Bill writes here. Formulas have been cited whose relevance is unclear. You talk about virtual images, others don't. Even the details vary; you've stated that relaxed viewing occurs at a focus distance of around 1m, while other sources say around 6m (optical infinity) which also seems to be what Bill is suggesting by "staring". I'd be glad to have this issue coherently resolved.

When I mentioned that Bill's observations are consistent with my theoretical research, I was referring to the general fact that focusing is a complicated and difficult affair and that this is an important subject that needs to be studied and explored further. I was not referring to Bill's specific suggestion (staring at the subject before bringing up the binoculars). Nonetheless, Bill's suggestion is an interesting practical method that deserves to be considered and investigated. I have not tried it myself yet.

I can provide two technical justification's for Bills method:

a) By starting, the user's eye accommodates for a long distance (as tenex correctly mentioned, a few meters is "practically infinity" as far as accommodation is concerned). If the user brings up the binoculars and can manage to adjust the focus wheel quickly to get a sharp image, then it is likely that his eye's state of accommodation will remain the same and the binoculars will focus such that they produce a virtual image at a few meters from the user's eye. This technique, if successful, can prevent the user from focusing the binoculars such that they create an image too close to the eye (e.g. at 30 cm). It is this latter case that creates most eye fatigue.​

b) The human eye already has an autofocus system. By adding a second focusing mechanism (the binocular's) in tandem, we are creating a very complicated and unstable feedback control system. The only way such a system can stabilize is that one controller is operating and stabilizing much faster than the other.

The human visual system responds to a "step change" in accommodation demand with a lag of about 0.4 seconds. It then needs an additional 0.6 to 1 second (on average) to reach at and settle on the new state of focus. Bill's method can be interpreted as an attempt to keep the eye's accommodation state constant while the binocular's focus being adjusted to match the eye's far focus state. If the eye tries to accommodate at the same time while the binocular focus wheel is being turned then the user's "focusing experience" can become very unpleasant.
​

Cheers
-Omid

 

[WJC]

206018

Hi Omid,

Thank you kindly for the substantiation.

Indeed, “focusing is a complicated and difficult affair.” That is very true, at least for those nitnoids who feel knowing all the ins and outs of the subject somehow makes them more opto-studly—someone to write home about. But by simply learning to stare, the problem has been decreased by at least half. Einstein said, “Any fool can know; the point is to understand.” I would temper that with KNOWING whether knowing is adequate for your own needs. For some people UNDERSTANDING is essential. That way they can—from practical experience—offer it to those who just need to know. A key feature of this situation is to know on which side of the fence you belong. There is no right or wrong answer, only the answer that concerns you.

While in the Navy’s Opticalman “A” school, I was required to learn all the mathematics, diagrams, and such relating to binocular collimation. Master Chief Opticalman (PICM) Lou Corriveau, who was going to my first ship with me, told me that if he saw me dealing with all that math, compasses, and protractors when we got to the fleet, he would no longer consider me an “Opticalman.” He was absolutely correct.

One fellow who once haunted these pages, but who has now taken up residence elsewhere, is spending an inordinate amount of time trying to learn all the diagrams and formulas. I don’t agree with his real reason for doing so, but ... whatever. However, I can collimate at least one binocular while he is sketching his first drawing and has yet to touch the binocular. That wouldn’t be a fair comment if I hadn’t tried to offer him the REAL WORLD take on the matter.

There are some major differences between academic and practical optics. Knowing the differences can save one a mountain of time.

I have been taken to task for saying that 100% of the myriad binocular collimation tips currently on the internet ARE WRONG. Is there a difference between clinical collimation and the many conditional alignment “tips” on the Internet? Oh yes. Can some of those tips make a bino serviceable with little or no eyestrain? definitely. Is it collimation? It is not.

The same level of understanding and care surrounds the subject of focusing. Some people care; most don’t. They would rather suffer a bit than to admit that it matters. To each his own.

Cheers,

Bill

 

[tenex]

The human eye already has an autofocus system. By adding a second focusing mechanism (the binocular's) in tandem, we are creating a very complicated and unstable feedback control system. The only way such a system can stabilize is that one controller is operating and stabilizing much faster than the other.

Thanks, I know Bill has (essentially) said this before, but you hadn't, and it's finally sinking in for me as something I intend to pay more attention to in the future, especially when I have the impulse to fiddle with focusing or diopter setting.

 

[lofapco]

Thanks for this topic.... It is all really excellent information to a person like me who is new to using binoculars and have been doing my best to learn how to properly focus.

 

[WJC]

That takes us to more minutia. I don’t know when it was, but some optical goober was successful in directing observers to focus by placing a hand over the objective of the “other” telescope. That seemed not enough for yet another, who insisted observers fish out an objective (obi-jay to us Opticalman types) and cover the objective of the other telescope.

1) This claptrap could be avoided by learning to stare.

2) There is no mention of the fact the bird may have flown away a few seconds before finalizing his instructions.

3) People come to binocular forums for all kinds of reasons. Some benefit the group; some only themselves ... pity, really. :cat:

Bill

PS Focus changes slightly—or big time—with the change in viewing distance. That matters a great deal to bird watchers. However, if you’re an amateur astronomer and find your target rapidly changing its distance, you have considerably more to worry about than focusing a binocular!