Diopter adjustment and eye focus fatigue? (1 Viewer)

wdc · Jan 30, 2017

I have found that after a few hours of birding, that my individual focus requirements begin to drift apart through the binoculars. In other words, when I start out, I don't notice any need to set the right diopter differently, but after a few hours, I'll encounter a view where its clear my eyes are not equally sharp, and I must resort to the diopter to set things right.

I do wear eyeglasses when viewing.

Do others find this to be a common condition?

Bill

Pileatus · Jan 30, 2017

wdc said:
I have found that after a few hours of birding, that my individual focus requirements begin to drift apart through the binoculars. In other words, when I start out, I don't notice any need to set the right diopter differently, but after a few hours, I'll encounter a view where its clear my eyes are not equally sharp, and I must resort to the diopter to set things right.

I do wear eyeglasses when viewing.

Do others find this to be a common condition?

Bill

Yes and it can actually become quite a nuisance. On sunny days it's common to get a mild sunburn on the eyes, especially after extended viewing (e.g. hawkwatching). I endured a bout of photokeratitis in my teens on a very bright winter day (snow blindness) that left me nearly blind. As kids we didn't have sunglasses, which is why we squinted a lot!

Other common causes are plain old-fashioned eye strain from steady viewing through a binocular or scope. When I look through my scope with my dominant right eye it doesn't take long for the pupil to contract in response. If I change to the left eye the image suddenly "brightens". After extended time on the scope it takes a bit of time to adjust to a "normal" binocular view with or without bins.

Sometimes a diopter adjustment works. At other times my eyes are just too fatigued to adapt and all images look crappy. Lighting is an essential ingredient and whether or not I'm wearing prescription sunglasses. We talk about bins far too much. The hourly health of your eyes and what you put between your eye and the optic are often the deciding factors.

wdc · Jan 30, 2017

Thanks for the response. Its good to know I'm not the only one.

After posting this, I did see some related links to other diopter threads. I think it must be a combination of fatigue, plus perhaps straining too much to glean detail in certain views. I will try to follow what Bill Cook advised in one thread, which is to relax the eyes and let the binocular do the work.

I've also experienced the burning of the eyes due to bright light exposure at high altitudes when painting. Now I wear sunglasses as much as possible, only removing them to paint. It helps. As for burning one's eyes while viewing through binocs, I can see how hawk watching could exacerbate the problem. You may have to resort to looking for skulking ground birds in dense shrubbery as a remedy!

Pileatus · Jan 31, 2017

wdc said:
Thanks for the response. Its good to know I'm not the only one.

After posting this, I did see some related links to other diopter threads. I think it must be a combination of fatigue, plus perhaps straining too much to glean detail in certain views. I will try to follow what Bill Cook advised in one thread, which is to relax the eyes and let the binocular do the work.

I've also experienced the burning of the eyes due to bright light exposure at high altitudes when painting. Now I wear sunglasses as much as possible, only removing them to paint. It helps. As for burning one's eyes while viewing through binocs, I can see how hawk watching could exacerbate the problem. You may have to resort to looking for skulking ground birds in dense shrubbery as a remedy!

I will say that my prescription polarized sunglasses are a true blessing on a bright day. I lose some FOV but the relaxation factor is worth it.

Bill Cook was/is correct and it's why I argue for the best bin one can afford. I don't give a darn what label is on the frame or how much it costs. I do care about an easy view that lasts all day long and, for me, that means alpha quality. There's a reason I see a lot of gray-haired birders using expensive optics.

CliveP · Jan 31, 2017

I've had a few bins lately that gave me eyestrain and it seems that they were both slightly out of colimation meaning my eyes were constantly straining to line up both images and I would end up with a headache but the problem was not obvious and the bins seemed pretty much fine initially.

Before I realised what was wrong I would have taken to constantly trying to adjust the binocular but now that I have both bins concerned fixed, I have no problems at all with them.

If you aren't sure, see if you can try another good working bin -maybe from a friend or something- for a while and see if you are still having the diopter problem. If not then get your bins checked out or get something else.

I normally check the diopter to optimise it when I begin a day out as my eyes can vary from day to day a little but once I've done that initial set check then I never need to do it again for that day.

typo · Jan 31, 2017

wdc said:
I have found that after a few hours of birding, that my individual focus requirements begin to drift apart through the binoculars. In other words, when I start out, I don't notice any need to set the right diopter differently, but after a few hours, I'll encounter a view where its clear my eyes are not equally sharp, and I must resort to the diopter to set things right.

I do wear eyeglasses when viewing.

Do others find this to be a common condition?

Bill

I've only noticed it when the light levels change significantly. I presume I need a slightly different setting when my pupil is 2mm from that when it's 4mm. It seems to be my right eye is the one that changes.

I have an ongoing discussion with my optician about what the room light levels should be. My pupils are 4.25mm at his standard test conditions.

David

iveljay · Jan 31, 2017

It isn't just optical stress as others have noted, on most bins I am about zero dioptre adjustment unless the thing has a manufacturing set up error.
However when fraught, tired, (or trying to test a new pair of binoculars in bad weather with steaming up eyepieces) I seem to drift off to -1 consistently.
I now treat this as a sign that I need to stop and get a cup of coffee otherwise I enter into a pathelogical constant resetting of the dioptre adjustment somewhat spoiling what was usually a good day up until then. It is a bit like having a nagging itch, anyone know a good book on Zen for binocular owners?

Binastro · Jan 31, 2017

Zen and the Art of Motorcycle Maintenance.

My eyes get tired quickly nowadays, but if I rest for ten minutes looking at nothing, my eyes recover.

Astronomers frequently change focus over a night, as the eyes change.

As our accommodation lessens with age, more frequent changes are needed.

chill6x6 · Jan 31, 2017

Pileatus said:
I will say that my prescription polarized sunglasses are a true blessing on a bright day. I lose some FOV but the relaxation factor is worth it.

Bill Cook was/is correct and it's why I argue for the best bin one can afford. I don't give a darn what label is on the frame or how much it costs. I do care about an easy view that lasts all day long and, for me, that means alpha quality. There's a reason I see a lot of gray-haired birders using expensive optics.

Yes! You don't always get what you pay for, but you sure don't get what you DON'T pay for!

Binastro said:
Zen and the Art of Motorcycle Maintenance.

My eyes get tired quickly nowadays, but if I rest for ten minutes looking at nothing, my eyes recover.

Astronomers frequently change focus over a night, as the eyes change.

As our accommodation lessens with age, more frequent changes are needed.

This^^

Rest your eyes...they will recover,

wdc · Jan 31, 2017

Thanks everyone for your thoughtful responses. I don't think it is a collimation problem, as any binocular I've been using for more than a few hours gives me a similar result.

Resting the eyes periodically is good advice.

I've been using 8x42's as my regular bins, but may try a 7x42 to see if that relaxes the view a bit. My big realization with extended use of binoculars while wearing glasses is that it is equivalent to putting a prescription over a prescription, and becomes an issue of personal fit/comfort, accommodation, in addition to the quality of the view.

Chuck, as one of the forum members with a collection of quality optics, can you say which ones are the most eyeglass friendly?

Troubador · Feb 1, 2017

Why you might need to refocus or re-adjust your dioptre

Here is a passage written by Bill Cook which explains what can happen and why:

Why was following this optometrist’s advice wrong? Let’s start by following his instructions—focusing the right eye as directed—to find out. Bingo, your right eye is seeing a great image. But now, with the right eye sharply focused,
you turn the center focus wheel or flip the lever to focus the left eye. Since, however, there’s a 2 diopter difference(for example) in your eyes, and since the center focus wheel or lever was designed to focus both sides, sharply focusing your left eye has just defocused your right eye by 2 diopters. Something isn’t right. But, you did what your optometrist told you to do. So it must be you ... right? ...

... When both eyes are sharply focused on the target, having followed the correct procedure, you may return to the center-focus wheel for focusing at various distances, until the instrument is used by another observer or until one of the adjustments has been inadvertently reset. In doing so, you will be maintaining your dioptric difference regardless of the distance to the target.
For optimal image quality please remember these two additional points. First, just stare and allow the focus mechanism to do its job. Our brain wants things in focus quickly. So if you aren’t careful, and the disparity is small enough, it will force the eye’s ciliary muscles to stretch or compress the eyelens to bring the image to a focus. This, unless clearly within our range of accommodation, can only be done at the expense of some degree of eyestrain, especially over long observing sessions.

Frequently, those new to binocular observing will focus on a target quickly and expect the instrument to remain focused—at least at the given distance. However, let’s say you have a dioptric accommodation of 4 diopters and leave
the instrument at either extreme of that range thinking all is fine. As time goes on, observing may become problematic if your natural (at rest, at that distance) focus setting should be 1.5 diopters. That means being in a hurry has placed your focus at an accommodatable, but unnatural, setting. Then, as fatigue sets in, you may fidget unnecessarily with the focus or suppose there’s something wrong with your eyes or the binocular when neither is true—it’s just your understanding of how to accurately focus....

Lee

Diopter adjustment and eye focus fatigue? (1 Viewer)

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