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How to measure our own IPD (1 Viewer)

Rafael,

Thanks, a simple method indeed whose error clearly decreases as the distance to the "point" on which you focus increases. To get an estimate of my IPD I used to use a ruler and a mirror or visit my optician. Now I have an alternative simpler method.

Peter
 
For that method to give a reliable reading you are not only going to have to clamp the caliper but also clamp your head. ;)
For several years I was stupid enough to set my binoculars to the IPD my optometrist had measured instead of what seemed most comfortable. I think he erred (parallax?) by 1,5 mm. An instinctive setting, even with large exit pupils can be quite consistent.

John

PS:- For really close distance viewing it is advisable to reduce the IPD. Of course the binocular axes won't converge as your eyes do, but it's easier to get the images to merge.
However, I find that the 1,5 m close focus of my 10x42 SV (whose objective spacing is around 10 mm greater than the ocular spacing) to be impractical for binocular viewing.
 
Last edited:
Tringa45 said:
For that method to give a reliable reading you are not only going to have to clamp the caliper but also clamp your head. ;)
For several years I was stupid enough to set my binoculars to the IPD my optometrist had measured instead of what seemed most comfortable. I think he erred (parallax?) by 1,5 mm. An instinctive setting, even with large exit pupils can be quite consistent.

John
Click to expand...

I believe the IPD measurements that you get from an optician are underestimates due to parallax errors. The method described by Rafael indeed requires that you try to keep the ruler and your head as fixed as possible---I don't find that to be a serious issue: I can press the ruler against a window, and do all measurement very quickly so that my head does not move.
 
PeterPS said:
I believe the IPD measurements that you get from an optician are underestimates due to parallax errors.
Click to expand...

If he were naive enough to try to measure from one standpoint, yes. But what's the point of transferring a potentially false measurement to your binoculars?
 
Tringa45 said:
If he were naive enough to try to measure from one standpoint, yes. But what's the point of transferring a potentially false measurement to your binoculars?
Click to expand...

John,

The IPD value that you get from your optician, or by any conceivable method (such as the one suggested in post#1), can be used as an initial estimate which you can tweak when using the binos.

Peter
 
I prefer to measure IPD by (1) using a binocular with small exit pupils to view a close object, (2) setting the bin properly for a comfortable view, (3) measuring the distance from the outside edge of one ocular to the inside edge of the other. The Leica 8x20 Ultravid, used to view an object at 6 feet, works very nicely for this procedure, which gives a good sense of the minimum IPD spec that should be accepted when purchasing a bin.

--AP
 
Alexis Powell said:
I prefer to measure IPD by (1) using a binocular with small exit pupils to view a close object, (2) setting the bin properly for a comfortable view, (3) measuring the distance from the outside edge of one ocular to the inside edge of the other. The Leica 8x20 Ultravid, used to view an object at 6 feet, works very nicely for this procedure, which gives a good sense of the minimum IPD spec that should be accepted when purchasing a bin.
Click to expand...

Sensible, accurate and practical. Also like the suggestion for establishing minimum IPD requirement for near focus.

John
 
It is difficult to believe that such a simple operation has taken on so many remedies. This is especially so when one takes our spatial accommodation into consideration or reads Rafael’s first post, again. And the distance to the object? We’re not stacking BBs here, but we’re getting pretty close. :cat:

Bill
 
WJC said:
It is difficult to believe that such a simple operation has taken on so many remedies. This is especially so when one takes our spatial accommodation into consideration or reads Rafael’s first post, again. And the distance to the object? We’re not stacking BBs here, but we’re getting pretty close.
Click to expand...

Bill,
Agreed that some are making mountains out of molehills here but I nevertheless think that Alexis' suggestion is very valid.
Many current 32 mm roof prism bins have a close focus capability of 2 m or less and objective spacing close or identical to the IPD setting (seldom the case with 42 mm roofs and larger).
Now although one can't get the optical axes to squint, there is a gain in viewing comfort at close distances if one reduces the IPD setting by a few Millimeters.
If a user with an IPD of 57 mm were interested in viewing butterflies and other insects, the choice of a binocular with a close focus <2 m and a minimum IPD of 56 mm would be less than ideal.

John
 
Tringa45 said:
I find that the 1,5 m close focus of my 10x42 SV (whose objective spacing is around 10 mm greater than the ocular spacing) to be impractical for binocular viewing.
Click to expand...

This might not work for you but it certainly worked for me.

Focus on any object at the minimum focus distance of your binos. Now close your left eye and look at the object. After a minute or so, close your left eye and look at the object with your right eye only. Notice that both views of the object are fine and comfortable. Now open both eyes and look at the object. Do not look at how the two overall views do not merge into one circle, that is not important, only look at the object of interest, and the view is fine and comfortable just as it was through one optical tube at a time. I did this 2-3 times and afterwards had no difficulty focusing always on the object of interest and ignoring the strange outline of the overall view.

Lee
 
Tringa45 said:
Bill,
Agreed that some are making mountains out of molehills here but I nevertheless think that Alexis' suggestion is very valid.
Many current 32 mm roof prism bins have a close focus capability of 2 m or less and objective spacing close or identical to the IPD setting (seldom the case with 42 mm roofs and larger).
Now although one can't get the optical axes to squint, there is a gain in viewing comfort at close distances if one reduces the IPD setting by a few Millimeters.
If a user with an IPD of 57 mm were interested in viewing butterflies and other insects, the choice of a binocular with a close focus <2 m and a minimum IPD of 56 mm would be less than ideal.

John
Click to expand...

200709

Hi John,

In THAT case, you are right on. Please remember that, as an old guy, my world has been shaped around the premise that binoculars were created to observe targets at greater distances.

Close focus opens a large can of misunderstanding. Some people, observing a distant target, may never have heard of collimation and have asked why their collimated binocular doesn’t offer, “the PROPER ‘figure 8’ field of view.” Deal with that once or twice a month for years and you, too, might become saturated.

And then, there are those folks who have been inundated with the popular—BUT WRONG—notion that binoculars are not collimated if the fields don’t overlap to a hundred billionths of an inch ... even though to get a good view of a dragonfly at 15 inches their rectus muscles are tying each other in knots and forcing them to focus—at least while looking for those “circles”—inside the bino ... ~1.5 to 2.5 inches from their nose! And what happens to your vision when you cross your eyes? YOU ARE NOT COLLIMATED!

As a gentleman, you were very kind in your correction. Bill Cook, however, is of NO consequence and truth is of supreme importance. :cat:

Cheers,

Bill
 
WJC said:
200709

Hi John,

In THAT case, you are right on. Please remember that, as an old guy, my world has been shaped around the premise that binoculars were created to observe targets at greater distances.

Close focus opens a large can of misunderstanding. Some people, observing a distant target, may never have heard of collimation and have asked why their collimated binocular doesn’t offer, “the PROPER ‘figure 8’ field of view.” Deal with that once or twice a month for years and you, too, might become saturated.

And then, there are those folks who have been inundated with the popular—BUT WRONG—notion that binoculars are not collimated if the fields don’t overlap to a hundred billionths of an inch ... even though to get a good view of a dragonfly at 15 inches their rectus muscles are tying each other in knots and forcing them to focus—at least while looking for those “circles”—inside the bino ... ~1.5 to 2.5 inches from their nose! And what happens to your vision when you cross your eyes? YOU ARE NOT COLLIMATED!

As a gentleman, you were very kind in your correction. Bill Cook, however, is of NO consequence and truth is of supreme importance. :cat:

Cheers,

Bill
Click to expand...

Bill:

I agree, binoculars are mainly used for distance viewing, otherwise, why in the world would you need one. ;)

So to find your IPD, focus clearly on a distant subject with any binocular, then take your ruler out and measure the space between the exact center of
the oculars.

So simple.

Jerry
 
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