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Problem with focusing /diopter setting

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#1 Marko F.

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Posted 05 December 2005 - 12:01 PM

Does anyone know what can be the cause of this problem I have come across:

On some binocular models I have found it impossible to find the right diopter setting that would suit my eyesight.

For example, on a certain high-end 8x42 model, which I bought last year, I kept changing the diopter setting many times, but it never worked right for me. If I got both sides of the binocular focused on a distant subject, then the focus wouldn't be right while looking at a subject at a closer distance.

After three days of trying to get it adjusted, I had to return the binoculars to the store. There the shopkeeper inspected them and found nothing wrong with them ! I got my money back, all the same.

On most other binocular models I have had no trouble getting them adjusted. Strange thing, isn't it.

#2 EdZ

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Posted 05 December 2005 - 12:26 PM

I don't think it's so unusual that you would have to adjust the right diopter for close versus far.

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Posted 05 December 2005 - 12:44 PM

Why would you expect the focus settings for a far away object to be applicable when viewing something much closer? This should be expected IMO.

What do you call "distant" and "closer"?

#4 Marko F.

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Posted 05 December 2005 - 02:28 PM

All guides and instruction leaflets that I have read, tell me that once I have found the correct diopter setting, it should be possible to focus to all distances without any further diopter adjustment.

And that's exactly how at least five different binoculars have worked for me.

What surprised me was that this certain high-end pair of binoculars worked differently. I could find no diopter setting that would work throughout the focusing range.

If this is a common feature of binoculars, I didn't know.

#5 Marko F.

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Posted 05 December 2005 - 02:45 PM

What do you call "distant" and "closer"?


Horizon and 10 metres (30 ft.).

EDIT: Spelling mistake corrected :p

#6 patter1

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Posted 05 December 2005 - 03:26 PM

In really cheap binocs, slack in the central focuser can cause this, but I wouldn't expct that in a good binoc. Ed and NW seem to be saying that binocs are supposed to do this...presumably for optical reasons. I never knew that...this is the first time I heard that. Explanation, anyone?

My cheap but very decent 7x35 binocs don't need diopter adjustment when viewing very close (about 10 feet) to very far (hundreds of feet).

#7 Claudio

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Posted 05 December 2005 - 04:55 PM

In a high end glass the focusing mechanism should work properly, therefore the cause of your focus trouble should be not there.
At close distances Porro binoculars could need right dioptre re-adjusting more than roofs, because of the bigger distance between the objective lenses.
However I think that trouble with IPD setting and right dioptre setting in high end glasses is mainly caused by spherical aberration of the exit pupil (see threads) not minimized by a perfect position of the eyes (centred and at the RIGHT eye relief).
Obviously it could also be that the sample you bought was a lemon.
Claudio

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Posted 05 December 2005 - 07:38 PM

once I have found the correct diopter setting, it should be possible to focus to all distances without any further diopter adjustment

Oh, that's what you meant. Your original post was some what misleading. Ok, then...I'd say something strange is going on. Like what Claudio said, you may have bought a bad bin. Out of curiosity, which brand was it?

#9 Pinewood

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Posted 05 December 2005 - 10:34 PM

Claudio seems to be on the right track. Yesterday, I was using a Swift Audubon 8.5x44, model 804, NOT the new model with the flimsy bridge. I was obliged to make large changes in the dioptre setting while using it, something I had not noticed with other glasses. I concluded that the problem was that I may have not aligned the target for both left and right focussing on dead center. I think this may be easier to do improperly than not having my eyes the proper distance from the oculars.

Clear skies,
Arthur

#10 Marko F.

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Posted 06 December 2005 - 03:40 AM

Oh, that's what you meant. Your original post was some what misleading. Ok, then...I'd say something strange is going on. Like what Claudio said, you may have bought a bad bin. Out of curiosity, which brand was it?


Ok, sorry for my bad language, I'm not a native English speaker. :crazy:
It was a pair of Nikon HG 8x42 (or Venturer LX in some countries), brand new from a specialist store.

I also found the center focus extremely difficult to use due to its fast ratio. But the main problem was that I couldn't set the diopter setting to work properly even after three days of using the binoculars.

The storekeeper (an experienced optics dealer) did a thorough test of the binoculars, and found nothing wrong with them !

And those were not my first binoculars, I was not an unexperienced user. So it was really a mystery to me what was wrong.

I am now using a Swarovski EL 8,5 with no trouble whatsoever.

#11 Claudio

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Posted 06 December 2005 - 04:52 AM

I own a Nikon HG 8x42, its exit pupil is well corrected, thus spherical aberration cannot be the cause of focus trouble. Actually the view through this 8x42 is one of the most relaxing I experienced, being right IPD and right dioptre adjustment not critical to set.
The focus mechanism in this binocular is very good; its quick but smooth focus should be a help more than a hindrance. However, click stops are too few, and probably they often don’t fit the correct dioptre adjustment the user needs. In fact I have to leave the dioptre ring popped up half way between two click stops.
Note that, as usually, in this Nikon the dioptre correction of the right eyepiece should be set looking at an object at far distance but starting with the right dioptre ring positioned at the closest focus and turning it in a clockwise direction. If you turn it in a counter clockwise direction the adjustment could be not so precise.
Claudio

#12 Marko F.

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Posted 06 December 2005 - 05:29 AM

Maybe it has something to do with the click stops you mentioned, Claudio. I didn't do any experimenting with the adjustment ring in between click stops. I was really annoyed by the whole business, because I haven't run into this sort of problem before.

As to the fast centre focus, of course that's more a matter of taste, and I strongly disliked it. My Swarovski's slow focus action suits me better.

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Posted 06 December 2005 - 08:31 AM

Marko, I am glad that you are not without binoculars due to your unfortunate diopter problem. I am still not sure what to think of the problem you had with your Nikons. Very odd.

#14 Marko F.

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Posted 06 December 2005 - 09:14 AM

Marko, I am glad that you are not without binoculars due to your unfortunate diopter problem. I am still not sure what to think of the problem you had with your Nikons. Very odd.


Yes, this Nikon problem made me turn into a "Swarovski guy". And soon I'll be the owner of an Orion Mini Giant 12x63 also.

#15 johnno

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Posted 06 December 2005 - 09:24 AM

Hi All,
I'm with you NW,I cant understand it either.
With my very limited knowledge,I believed most peoples eyes have slight differences,between right and left and the diopter adjustment was to correct for this,and allow both eyes to focus together as a unit regardless of the distance.
IF the diopter setting is done correctly,then there should be little need to reset,although if the diopter was set at infinity and a subject was then viewed up close that may cause a problem and vice versa.
I allways thought though,that the reason it was calibrated,was so you could reset to YOUR perfect setting for YOUR eyes,if someone else used your binoculars.
If that is NOT the case,there seems little point in providing a calibrated setting,if it has to be moved by the main user all the time.
Perhaps the binoculars are faulty,and unlikely as it seems,the eyepieces are not moving uniformly.

Regards.John

#16 Marko F.

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Posted 06 December 2005 - 09:38 AM

Perhaps the binoculars are faulty,and unlikely as it seems,the eyepieces are not moving uniformly.

Regards.John


Yes, it certainly felt like the binoculars were faulty. We'll never know since I returned them.

I do know that my eyes do have a dioptre difference (usually I have to adjust the right dioptre to about +0,25)and I have slight astigmatism (so slight that I use binoculars without glasses).

But still, all other binoculars have worked fine with my eyes.

#17 EdZ

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Posted 06 December 2005 - 09:45 AM

I picked up a 20x80 and went outside this morning. first I focused on a object about 200 yards away and set right diopter. Then I set it to close focus, about 150 feet. The right dipoter reading varied between these two focus distances by 1 dipoter.

I just took my Nikon SE 12x50 outside to do the same test. first I focused at about 200 yds and noted the right diopter. then I focused at about 40-50 feet. I needed to adjust the right diopter by 1.5 diopters.

I'm thinking this is something i do with every binocular. I think this is normal. My guess is it probably has to do with my eyes more than anything else.

edz

#18 Marko F.

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Posted 06 December 2005 - 10:25 AM

Edz, it would seem to me that some people's eyes just aren't compatible with some binoculars. My eyes weren't compatible with the Nikon, and your eyes are not compatible with those binoculars you mentioned.

I still would say that someone with normal (or "perfect") eyesight shouldn't have to alter the dioptre setting after its initial setup.

Anyone agree with me ? What have other binocular users experienced ?

#19 EdZ

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Posted 06 December 2005 - 10:39 AM

I just did the exact same test with a Pentax PCF WP 10X50. I got a difference of 2 diopters on the right eye focus.

You can't honestly believe that three different brands of binoculars aren't compatible with my eyes?

another one Swift Ultralite 8x42. I got a 1 diopter difference.

and another one Garrett Optical Genesis 10x50. I got a 1.5 diopter difference.

That's five different brands of binoculars, picked at random off the shelf. Every one varied by 1-2 diopters from 200 yards to near close focus.

here's another Nikon AE 12x50. This one only varied by maybe 1/4 to 1/2 diopter.

and another Oberwerk Mariner 10x60, varied by 1/2 diopter.



edz

#20 Marko F.

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Posted 06 December 2005 - 11:03 AM

EdZ, I really don't know, but obviously there is some variation in how different people see with different binoculars (and how often they need to adjust the right dioptre).
My limited knowledge of optical theory really leaves me with no explanation.
But I honestly thought that no-one ever touches the right dioptre adjustment after it is initially set. Well, you proved me wrong!

#21 Sarah88

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Posted 06 December 2005 - 11:27 AM

I find that I need to adjust the right eyepiece for close-focus too.

Mostly I use binoculars at infinity, and I find that I qlways need to adjust the right eyepiece slightly positive - usually about +1 diopter, but it does vary a bit from one binocular to the next.

For close-focus, they all need to be adjusted slightly towards negative from their usual +1 positive setting.

#22 johnno

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Posted 06 December 2005 - 12:15 PM

Hi All,
MARKO,And EDZ.
Marko,that has allways been my understanding,re the diopter adjustment,ie once set,it should be correct for THAT user over all distances.
Quite obviously,as YOU,EDZ,and I suspect many other people, need to adjust for different distances,it would seem, the diopter setting is not as stable,for SOME PEOPLE,as OTHERS.
I find this a little confusing,as for eg,how often do we CHANGE the IPD setting,which is also calibrated,for an INDIVIDUALS use.
I would think almost never, UNLESS someone else uses our Binoculars and moves them,so
Why CALIBRATE the diopter setting,if it is not meant to be a STABLE REFERENCE.
The focus setting is not Calibrated,and,of course, we change it,even when looking at "INFINITY OBJECTS"
The only answer I can think of, is the reason the diopter is calibrated is for an individuals TYPE of viewing,ie close or distant.

In Simple terms,(which suits me, Kathy thinks I am simple anyway),
if you ONLY look at birds up close,then you set the diopter for THAT viewing Range,OR,if you tend to use your Binoculars for Astronomy,then set your diopter for Infinity.
It would seem,the differences,and condition,of an individual's eyes play a very major role,in ALL aspects of binocular Use.
As an almost 57 y/o insulin dependant diabetic,drinker smoker,I know,even dark adapted,my eyes DONT see,Detail,which is easily seen by my Grandkids.
yet, I dont Need glasses,except for reading.
Maybe BILL COOK,can shed some light here.

Regards.John

#23 Marko F.

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Posted 06 December 2005 - 12:22 PM

Ok, here's my new "Theory regarding the Human Eye and its optical characteristics in regard to the internal workings of the mechanical Bin-Ocular, especially its Dioptre Setting screwe":

1) Some people take a binocular, adjust the right dioptre setting to zero, and just go on viewing without having to make any adjustments to the dioptre setting.

2) Some people take a binocular, make an adjustment to the right dioptre setting that corresponds to the focus difference of their two eyes. They can then carry on viewing without any further adjustment of the dioptre setting. This would mean that one of the persons eyes is short-sighted in relation to the other eye, and the right dioptre setting compensates for this.

3) Some people take a binocular, and they first adjust the right dioptre setting to compensate for the focus difference of their two eyes focused to a certain point, but they still would have to make adjustments of the dioptre setting, because of a certain characteristic of their crystalline lenses (the lens inside your eye), perhaps due to a difference in the flexibility of these lenses.

4) Some people (like myself) might find that most binoculars work as I describe in 2) but SOME binoculars work as I describe in 3) This would perhaps be because they have a slight difference in the flexibility of the crystalline lens, but with most binoculars they manage to see well without having to adjust the dioptre setting. But a certain feature in the optical design of SOME binoculars (such as the Nikon HG for me) somehow MAGNIFIES this difference, and the result is that the person needs to adjust the dioptre setting when changing the focus distance.

End of theory.
Give me a diploma in optics, (or just send me to some asylum. Your choice. ;) )

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Posted 06 December 2005 - 12:31 PM

Like Sarah88, I have only used my bins at infinity and thus cnce I set the diopter, that's it. I have been naively assuming that once it was set, the diopter setting was basically there to stay. Some people are short sighted and near sighted. Would that have anything to do with this?

#25 KennyJ

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Posted 06 December 2005 - 01:36 PM

To throw another spanner in a works already so much more complicated than it ought to be , as I've reported once or twice , a long time ago now , SOMETIMES , even with the SAME binocular , I need to adjust the right diopter DIFFERENTLY from what I might have done the previous day , to attain what I perceive as being PERFECT FOUCUS , even on an object at exactly the same distance !

I don't expect anyone to try to explain that , but it MUST be that some days my short - sightedness in my right eye is not as " slight " as it appears to be on other days .

There must be bio - chemical reasons for this .

Perhaps , for example , if I'm VERY tired , or my eyes have been focused on something close ( such as a PC screen ) for hours ( or even a combination of both ) then maybe the muscles in my eyes just cannot work hard enough to make the adjustment required to focus from close to far distance .

In ADDITION to this ( as if this isn't troublesome enough )SOME days ( and nights ) I've found myself having to do the same kind of thing which EdZ has described , altering the right dioptre to compensate for different distances , whereas on other days , everything seems to work just like all those minimilistic instruction leaflets suggest .

I would add that these problems ARE minimised , IF , instead of closing the right eye first , whilst adjusting the centre focus wheel for the left eye at a distant object , I actually CAP the right objective , and leave BOTH eyes open while making that adjustment ( which IS absolutely CRITICAL to get RIGHT )

Then cap the LEFT objective and keep both eyes open while VERY carefully adjusting the right diopter for the right eye at that same distant object .

It is also CRITICAL to get the IPD set PERFECTLY for THAT object at THAT distance .

I apologise if this latter section of the post is akin to teaching your grandmother to suck eggs , but it continues to AMAZE me how many people just do NOT know how to properly focus a " centre - focus " binocular .

And just before I finish , with the only INDIVIDUAL eyepiece focusing binocular I have , the Captain's Helmsman -- I EXPECT to have to adjust BOTH oculars for EVERY different distanced objects I happen to be looking at -- and when I do -- boy are the images CRISP :-)

Even THAT is FAR from what everyone else and their dogs have ever proclaimed about IF binoculars .

THEY say , " Just set to " 50 feet " and away you go "

I say " RUBBISH " :-)

Regards , Kenny


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