Dioptre adjustment ranges for different binoculars? (1 Viewer)

[pompadour]

Something which should be useful to many, that I've been v. much needing to know for myself. What is the actual dioptre adjustment range in different makes of binocular you know of? I'm assuming it doesn't vary much among models within a make, but if it does then for such models please! Thanks.

Useful for those with short or long sight who like to use bins - maybe only sometimes - without glasses (a) if there's an imbalance in the eyes, or (b) for the short-sighted to focus "infinity" (i.e. the distance beyond which further focusing is not needed). The latter requiremt. is sometimes called "overrun past infinity", the word there referring to infinity for the normal-sighted.

What's needed is from your own experience. The website figures are not always correct. E.g. Swarovski and Zeiss both state ± 4 d but this is understated, each going to at least ± 6 from what I gather. As for the markings at the adjustment ring they may not be accurate, or not represent dioptres, and may show more than or less than the actual possible movement there.

In my present bins (alphab. order) -

Barr and Stroud: more than 4.5
- my short sight is presently at that stage!
Kowa: more than 4.5
Leica: about 4, estimated
Nikon: more than 4.5
Zen-Ray: more than 4.5

I gather -

Swarovski: at least 6
Zeiss: at least 6.

(Thought of posting this at last when I saw a new thread today in the Leupold subforum on the same subject - in regard to one model.)

 

[John Russell]

Pomp,

I think the diopter range quoted by the manufacturers could be relied upon as an absolute minimum and it may be significantly more in the high magnification versions of a binocular family. There can be very few users though with really big differences between both eyes.

As regards focus overtravel, Zeiss bins have a very generous amount. I read one test report of the old 8x30 Conquest, which had a focus overtravel in excess of -10 diopters!
It would be wise though for the severely myopic to test infinity focus before purchase.

John

PS:- The Steiner Discoverys have a diopter setting on both oculars. This would enable the user to tailor infinity focus or close focus according to their needs.

 

[pompadour]

John, I don't know the relevant stats at all but had thought a big difference between the two eyes is indeed very rare (in my case it's recently been ≤ 0.5 d). So, I have assumed wide adjustments are provided mostly for overtravel /overrun /overdrive past infinity for short-sighted people to use bins without wearing specs. Didn't know about that 10!

 

[John Russell]

So, I have assumed wide adjustments are provided mostly for overtravel /overrun /overdrive past infinity for short-sighted people to use bins without wearing specs.

Pomp,

The diopter setting is there to compensate for the diiference, so it could only provide more focus overtravel for the right eye.

John

 

[pompadour]

John, are you sure? I thought the range is provided for in each barrel, L and R. Suppose the user's eyes are -2 d L and 0 d R. He sets the dioptre ring, on the R barrel, to +2. Now when the R eye focuses at infinity won't the L optical system be set at what is infinity for an eye at -2 d? That was my reasoning.

 

[John Russell]

John, are you sure? I thought the range is provided for in each barrel, L and R. Suppose the user's eyes are -2 d L and 0 d R. He sets the dioptre ring, on the R barrel, to +2. Now when the R eye focuses at infinity won't the L optical system be set at what is infinity for an eye at -2 d? That was my reasoning.

Yes, Pomp, that's correct. Perhaps I misunderstood you.
That setting would provide a synchronous difference between barrels of 2 diopters throughout the focussing range but it can't provide any help with focus overtravel for the severely myopic.

In some cases the manufacturer might be able to modify the bin to provide more infinity focus overtravel, but this would be at the expense of minimum close focus, at least for the normally sighted.

John

 

[mooreorless]

I would think the best thing to do would be to contact the manufacturer and see if they would adj. diopter control later if need be. I am -2 in left eye and right is plano

 

[pompadour]

Steve, thanks, but for myself need the info to see what models I can get. In what I already have (presently) there's a problem only with Leica, and I've never heard of them doing that for a customer, and also, since they're famously tight with dimensions (for compactness), maybe it's not possible. But my short sight is getting less so (myopia's reversing) and am now at -4.5d R and -4.0d L and hoping the vision in both eyes will cross Leica's -4d limit soon! At this moment would ideally like, for the near future, Celestron roof, Kowa roof, Meopta and Zeiss - in certain combinations, and of these Zeiss is fine at -6d, Meopta is discouraging with their website stating ±3d, and the Celestron and Kowa info is unknown. It is such data I seek to know correctly, and that'll be useful to many, who like to use bins with their specs off. (Not trying to start a collection! Wish ideally to have three bins in a certain combin. of configs.)

 

[OPTIC_NUT]

Pompadour, this may help clarify your assumptions:

Observation-1) The diopter adjustment is for BETWEEN eyes, not for each eye.

Observation-2) When the correction for either eye gets to around -4.0 diopters,
you actually run out of focal range for many binoculars.

My correction is at -3.75 for both eyes, so I have problems using some binoculars
because the total adjustment won't quite get me focused at infinity.

Your eyes, at " -4.5d R and -4.0d L ", should be no problem for the diopter correction,
but can be a big problem for the focal "travel range" mentioned above.

So, I believe you are trying to fix a problem with a mechanism that can only
work for one eye. Unfortunately, I haven't seen published information about
the total focal range (how far it can go to correct for eyes at infinity).

If you want to use your binos without eyeglasses, there are correction lenses made,
but only for certain cameras and telescopes.

But all is not lost. If you buy a pair of -2D or -3D or -4D circular lenses a little
bigger than your ocular diameter and clap them over you oculars with little dots of
removable adhesive (beeswax or silicone perhaps), you will set the focusing range
of your binoculars where it keeps your eyes happy.
Then you won't have to worry about missing any field of view.


Kowa and Leupold and most Nikons allow full field of view with eyeglasses,
by the way. Very old ultra-wide FOVs, too. I'm not sure about the rest.

(Technical note:
-2 Diopter lenses are listed as having a -500 mm focal length
-3 Diopter lenses are listed as having a -333 mm focal length
-4 Diopter lenses are listed as having a -250 mm focal length
..and anywhere in that range will probably adapt your binoculars to you )

 

[pompadour]

O_Nut, thanks and appreciate the useful and interesting info. Did think a bit on those lines, and that it may be better to request in the first post of the thread ideas on the technical basis from those who know, and then proceed. But also wished to state soon what I seek: which models alow how much overrun past infinity for the short-sighted. From my experience and what I read in Bf. had gathered that many makes allow enough for me and many makes don't.

Whoever else too, pl. be frank about any errors here. This is my reasoning for thinking the allowance applies to both barrels (an expansion of what's already said to John). Let's take a model with adjustment of ±5d in the R barrel (the usual side), a range relevant to both of us (O_N and me). A user (hypothetical) has -5d short sight in the R eye and normal vision in the L. So he sets the ring to -5. He can now focus infinity with the -5d R eye. The optical system of the R barrel allows this. Now, a user has vision the other way round, 0d R, -5d L. He sets the adjustmt. (which is in the R barrel) to +5. Now the L optical system allows the -5d L eye to focus infinity. Thus in each barrel, R and L, the focusing element can move to a position (/limit) which allows a -5d eye to do so. A user has -5d vision in each eye. The ring is set at 0. To focus infinity the focus control moves both elements together to the position which enables this.

 

[OPTIC_NUT]

Oh...I see:

---You know about the gross focus range of various binoculars,

----But you are looking to see if any are knocked out of the running because of
their left-right adjustment range.

You only have a 0.5D difference, though. If you are that close to the edge,
I don't think this exercise will pay out reliably for you, over the day's eyestrain
or over the years or between different binoculars' fringes. Anything outside of +/-0.5D
seems like it couldn't possibly deal with your issue. Something in your
epistemics isn't adding up.


I also believe that playing at the outer range of a given set of binoculars places them
outside their design optimum range, whereas some occular correction would actually
put you in the center spot of the optical engineer's ray-tracing. This is from
observing some optical design work being done. The general principle is: the farther
from the source of error (ie, the eye) a correction is applied, the more difficult and
less effective the results. It depends on how precise you really want to be.

Anyway...just an opinion.
Best luck.

 

[pompadour]

O_Nut, thanks, but no, that's not it! I must be pretty hopeles at this whole thing - but also feeling a bit special as there cannot be many who convey the exact opposite of what they mean! I do *not* know gross focusing ranges and am *not*trying to see about L-R adjustments, but trying to *get to* know the former *from* the latter!

I.e. - a last time, if you'll bear with me! - seems to me that *if* a bin allows ±5d adjustment *between* eyes *then* a person with -5d vision in both eyes can focus infinity with that bin.

Don't feel bad about this, as it's *not vital* to me. In the field I do wear my specs, because without them I cannot see what the h* is out there to take a closer look at it! Just that I feel specs a bit of an imposition and like to avoid them whenever poss. At such times too I like to use a bin, to watch birds, or for whatever other magic it affords, and to see the far distance as well without the offending contraption. That - no prolonged use without specs - would also be relevant to your info on the limits of focus, and possible implication of eyestrain.

 

[OPTIC_NUT]

"
I.e. - a last time, if you'll bear with me! - seems to me that *if* a bin allows ±5d adjustment *between* eyes *then* a person with -5d vision in both eyes can focus infinity with that bin.
"

Assuming the binocular is out of range, the adjustment only allows one eye to
benefit from its range, because only one side has that adjustment.
I have never seen binoculars with both sides diopter-adjustable.
Just trying to understand.

 

[pompadour]

O_Nut, thanks for your continued patience. Your responses are v. valued by me, but if I'm still not makng sense you don't have to spend your time on this! Maybe no-one else after John has chimed in because my points are wrong or trivial.

Able to return to the computer only now. Before sitting down to it thought a bit more about the problem here. It may be I have not explicitly stated an assumption. I thought it's a reasonable one to make about the better-quality instruments. It's this.

Assumption: If the dioptre correction range (as stated by the maker, or reported, say, in Bf. - seems this is always wider than the stated figure) is -n d to +n d the optical system of each barrel allows an eye with vision at either extreme (even), - n d or +n d, to focus across the whole focusing range of the instrument, i.e. its close-focus limit to infinity.

 

[ceasar]

Correct me if I'm wrong but I think O-N is saying that (assume the diopter is for the right eye) you first have to use the center focus to make your left eye sharp. After that you adjust the diopter to make your right eye sharp. If there isn't enough diopter range to do this for your right eye you are out of luck.

Of course you may be talking about something else entirely.:h?:

Bob

 

[OPTIC_NUT]

Correct me if I'm wrong but I think O-N is saying that (assume the diopter is for the right eye) you first have to use the center focus to make your left eye sharp. After that you adjust the diopter to make your right eye sharp. If there isn't enough diopter range to do this for your right eye you are out of luck.

Of course you may be talking about something else entirely.:h?:

Bob

Close, but not quite...

If the Left (uncompensated) side cannot be brought into focus,
there is nothing the Right (diopter-adjusting) side can do to fix that.
You have hit upon the correct theme, though: diopter adjustment only
has an effect on one side.

 

[pompadour]

O_Nut, I'm not saying -n to +n vision focusing across the range, close limit to infinity, in the L barrel is a *consequence* (optical or mech.) of this being possible in the R barrel, but that I *expect it is provided* in the L so it matches the R in that respect. It's a qn. of fact - i.e. is that correct as a fact or not? Logically prior to that is a nother assumption. In any bin where the adjustment (at the R barrel) is -n to +n can an eye at -n focus at infinity through the *R* barrel?

 

[Troubador]

Assumption: If the dioptre correction range (as stated by the maker, or reported, say, in Bf. - seems this is always wider than the stated figure) is -n d to +n d the optical system of each barrel allows an eye with vision at either extreme (even), - n d or +n d, to focus across the whole focusing range of the instrument, i.e. its close-focus limit to infinity.

Pomp

My understanding is that, if, when adjusting the dioptre on the right-hand tube you need either the maximum minus adjustment or the maximum plus adjustment or anywhere in between, when you have finished and both barrels now are in focus for you, you should still be able to use the full focusing range of the binoculars, from closest focus to infinity.

Does this answer your question?

Leo

 

[pompadour]

Leo/Lee, thanks, yes, conditionally: if the R side can be set anywhere between the max. minus and max. plus adjustments *when the L eye has normal (0 dioptre) vision*. If you can then also use the full focusing range what I expect will be possible.

 

[OPTIC_NUT]

This would make sense if your eyes were about 5 diopters apart from each other.
You have given your prescription as only 0.5 diopters apart, however.