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Focusing Binoculars.


LukeSkywatcher
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Most (if not all) binoculars come with one eyepiece that can be adjusted individually. Since i was 6 yrs old i have been observing with bins and i was sure that the correct way to focus bins was to close your left eye first and adjust the eyepiece that moves independently and then open your eyes and focus both eyes with the central focusing wheel. 

However, today i got my new bins (Strathspey 10x50) and the instructions said to close my right eye and focus with the central focus wheel and then open both eyes and focus the independent eyepiece (the right hand side one).

Every set of bins i have ever owned always have the independently focusing eyepiece on the right hand side, so the Strathspeys are no different.

My question is: which method is correct?. 

Focus with the central focus wheel first and the the independently focusing eyepiece second or visa versa. 

Most likely a very stupid question because at the end of the day we all know what the view through a focused set of bins looks like.

I'm just puzzled.

Edited by LukeSkywatcher
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Without slightest doubt in my mind, one should first focus un-adjustable eye (regardless of whether it is RH or LH) and than correct the eye which has individual correction/adjustment, or...

get decent astro bins which normally have independent adjustment for each eye?

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I've always focused centrally first, focusing the fixed eyepiece then adjusted the, typically, rightside eyepiece using the +\- adjuster. Never heard of your method tbh. Surely, adjusting +\- first then using the central focus would throw the adjusted one out?

Or am I mis-thinking this?

Edit/ Nope. I think I'm correct :D

Edited by ghostdance
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Thanks all. Seems i have been doing things wrong for 30+ yrs. I cant see how it makes a difference because end result is focused bins.

So the way to go is centrally focus with both eyes open and then adjust the diopter (couldnt think of the word earlier) eyepiece?.

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Thanks all. Seems i have been doing things wrong for 30+ yrs. I cant see how it makes a difference because end result is focused bins.

So the way to go is centrally focus with both eyes open and then adjust the diopter (couldnt think of the word earlier) eyepiece?.

It must make a difference. If you get your diopter eye in focus then require adjustment or the other eye, then you will have to alter the focus on the dioptic....(made sence in my head)

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Centre Focus with right dioptre adjustment ?


Focus with the left eye only using the centre focus. When in focus, close/cover left eye and complete focusing with right dioptre/ right eye  only.


When focused, just use centre focus with Both eyes open.


That is the standard way to  set-up binoculars.


However, if you have independent focus eyepieces ie 2x dioptres then focusing can start with either eye

Edited by Charic
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With IF binoculars ( Individual Focus) you can avoid  in-accuracies with focusing ( check Steve Tonkins image here - http://binocularsky.com/binoc_basics.php   plus you can better proof the optics from extremes of hardship, ( knocks, moisture ) 

IF has its advantages and disadvantages. Space needs no constant adjustment of the focusing mechanism, but following and aerobatic display at an air show, requires constant focusing to keep the target image sharp. The Pentax PCW WPII binoculars have centre focusing with 'Focus Lock'. These were initially my first choice, however I was persuaded to buy some Nikon Extremes, where it went all wrong for me? I still need some 10x50 general purpose binoculars, and CF vs. IF is an issue to solve.

Once IF focusing is mastered, its like everything else, it becomes liquid smooth. Just defocus in one direction, then re-focus, until first sharpness is achieved, don't be back and forwards, just focus till first sharpness is achieved. some folk can do this simultaneously ?

Edited by Charic
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Talk to your optician - most of us are not symmetric.

I am heavily short sighted on the left and not too bad on the right.

The design caters for majority of people (who have one side weaker) - if both of your eyes are identical than the adjustability is superfluous (leave it at 0 and use central knob only).

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Just an update:

Today i took all of the above advice and tried to focus my 10x50 bins firstly by keeping both eyes open and using the central wheel, and then focusing the dioptre eyepiece. I found it a bit difficult to get complete sharp focus, so i switched back to focusing the dioptre first and then using the central wheel. This worked perfectly. There is nothing wrong with the bins, so it must be my eyes. Maybe 30+yr of doing it my way has somehow trained my eyes to except this as the norm.

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Just an update:

Today i took all of the above advice and tried to focus my 10x50 bins firstly by keeping both eyes open and using the central wheel, and then focusing the dioptre eyepiece. I found it a bit difficult to get complete sharp focus, so i switched back to focusing the dioptre first and then using the central wheel. This worked perfectly. There is nothing wrong with the bins, so it must be my eyes. Maybe 30+yr of doing it my way has somehow trained my eyes to except this as the norm.

You should only keep your left eye open and use the central focus. Focus until the image is sharpest with your left eye only.

Once you have sharp focus for the left eye, now close/cover that eye, or even put the lens cap back on, and only focus now with the right eye, using the dioptre setting.

When you have a sharp image for your right eye, now open both eyes/remove any caps, and just focus using the centre wheel.

your image should be sharp now for both eyes.

Edited by Charic
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Thanks all. Seems i have been doing things wrong for 30+ yrs. I cant see how it makes a difference because end result is focused bins.

So the way to go is centrally focus with both eyes open and then adjust the diopter (couldnt think of the word earlier) eyepiece?.

If it doesn't make a difference it's because your two eyes are not very different from each other. This is perfectly possible and no bad thing! If they are very different it may make a useful difference to focus properly (ie the fixed one first, then the adjustable one.) My eyes are very different but one is so useless that it hardly matters whether it is in or out of focus!!! GRRRR, such is life.

Olly

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If it doesn't make a difference it's because your two eyes are not very different from each other. This is perfectly possible and no bad thing!

I had my last eye test in March 2014 and was told that even though i wear glasses.......i had better then 20/20 vision.

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Hi all as you all know I've just had bought for me a pair of binoculars and the rules for focus in the the instructions where first close your right eye and focus sharply at a object using the centre wheel when you have the desired effect then close the left eye and on the same object get the same sharpness using the diopter then check by opening both eyes I done this inside and outside and the effects were the same brilliant I've recently been to the opticians to have a eye test and had to purchase two pairs of glasses one for reading and a pair for tv and he told me or rather corrected me when I told him I once had 20/20 vision and he said there's no such thing as 20/20 vision in the uk it's a American measurement but when I was younger I really had good eyesight but he explained how this deterioration comes about he was very good so maybe there are different ways for different binoculars who knows but that's what I did and it works every time :-) :-) Jimmy :-) :-)

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  • 2 months later...

Nobody seems to have mentioned its best not to close an eye when setting up the focus as that can cause your other eye to squint, covering one side with a lens cap is best then swapping over to do the otherside.(shouldnt really use your hand instead of a lens cap either as on larger binoculars stretching your arm out will change the orientation of your eyse to the binoculars)

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Nobody seems to have mentioned its best not to close an eye when setting up the focus as that can cause your other eye to squint, covering one side with a lens cap is best ...

It only gets mentioned about once a year:

http://stargazerslounge.com/topic/193055-new-10-x-56-bins/?p=2020759

http://stargazerslounge.com/topic/221290-strathspey-marine-7x50s-on-the-way/#entry2379690

... but I guess 2015 is your year....

:grin: :grin: :grin: :grin: :grin: :grin:

Edited by BinocularSky
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