Individual Focus Binoculars or Single Diopter Adjustment?

This BinoWizard question comes from a reader who has significantly different strength vision in each of their eyes and therefore is looking for a binocular that can compensate for this, but is unsure of exactly what to look for:

Have A Question For Me?Question:

Great site – what do you call binoculars the have separate focus for one eye? I need a pair of independent focus binoculars that allows me to do this as one eye is significantly weaker than the other. Is there a ‘phrase/term’ I can use for searching for this type of binocular?

BinoWizard Answer:

Great question and this is actually one that I get asked quite a lot as there seems to be a lot of confusion and general misunderstanding on exactly how to focus your binoculars and set them up for your specific vision.

Therefore I have decided to publish my answer as I feel it will be of benefit to a lot of BBR readers out there.

Single Diopter Adjustment

Many people have slight differences in the strength of vision in each of their eyes. Therefore any binocular worth its salt will have some way of making a dioptric correction to one eyepiece independently of the other and thus calibrate it to the differences in your vision.

Diopter Adjuster RingThis is known as the diopter adjuster (spelt dioptre in the UK) and is usually located on the right eyepiece, but some are integrated into the main focus wheel (see images on the right)

Once you have performed this calibration and thus made allowances for the differences in your vision, you simply use the binoculars normally and focus on objects at different distances using the focus wheel.

For more on this please check out my guide on how to focus your binoculars and set them up for your specific vision.

Diopter Adjustment located on the central focus wheelDioptre Adjustment Range on Binoculars
The amount dioptric correction varies from binocular to binocular and rather frustratingly not that many manufacturers indicate what amount of dioptric correction their models are capable of.

Then even when they do, I have read that they often advertise a number less than what they are actually capable of, so as to protect themselves.

However I think as a good rule of thumb, most will go from -4 to +4, many will achieve -4.5 to +5.5 and I have see top end models from Zeiss and Swarovski that can go from at least -6 to +6.

I am not sure what level of adjustment that you need, but if you feel that this is enough, just make sure the binoculars you are looking at have a diopter adjuster and if possible look for some where they advertise the amount of correction available.

There is also another option that I think will offer more or at least a different alternative that may help depending on the exact nature of your problem:

Individual Focus Binoculars

Individual Focus Binoculars - Diopter Adjustment on both eyepiecesYou also get binoculars with individual focusing for each side and basically these have diopter adjusters on both eyepieces, with most forgoing a focusing mechanism that adjusts both the sides at the same time, instead having a very long depth of view.

Often described as fixed focus, focus free or no focus binoculars, I would assume that these individual focus binoculars could be a better option if you don’t get enough dioptric correction with standard binoculars.

This is because you potentially get more compensation, indeed double the amount as you can set the right all the way to one extreme and the left all the way to the other.

I think this is also where the confusion can often come from as for marketing purposes this type of binocular has often been somewhat hyped up been described as being auto focus or self-focusing binoculars, which are other terms that you could look out for should you decide to go this way.

For more details on these, their relative strengths and weaknesses and links to the ones that I have tested and reviewed, take a look at this article on Individual Focus / Fixed Focus Binoculars.

I hope that this has helped. If you or anyone else has any further questions, suggestions or ideas, please feel free to use the comments section at the foot of the page.

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If you need some advice or can’t decide what binoculars are right for you, or perhaps you can’t understand a optical technical term or binocular feature that I have not already answered or written about, I will do my best to answer it for you: Ask The BinoWizard Here


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