Margin of error for interpupillary distance on binoculars

[timbernomad]

How essential is it for binoculars to be an exact fit for someone's IPD? My wife has an IPD of 56mm according to her optometrist. A lot of binoculars on the market start at 57mm or 58mm on the low end.

How much will the view be compromised if the IPD setting is one or two millimeters off? I am the primary user for the binoculars, but I'd hate to buy something that my wife can't also enjoy.

 

[Airohunter]

I also have a narrow IPD, around 55 seems to be my mark. I can tell you it makes a huge difference, 56's are just too wide and worthless to me regardless of the quality of optic.

 

[SikaSeeker]

IPD is one of the most important specs. Leica ultravid are good for narrower IPD. Think of how you can experience black outs or kidney beans if you misplace your eye on some binos

 

[TaperPin]

There are a number of compact binoculars that can be used with very narrow eyes - all the current rage are mid and full sized binos, but quality compacts give up very little to them. Older Leica compacts are very good.

 

[timbernomad]

bumping this to see if there's any other input

 

[TaperPin]

bumping this to see if there's any other input

There is a way to see how much of a difference it makes on your own binoculars. Carefully measure, then adjust 2 mm farther apart (about 1/16”) and test ‘em out.

I just happen to have a dial caliper and 10x32 Leupold Pro Guide HD here as we speak….1mm too wide could work, but 2mm requires a lot of work to keep perfectly aligned or the poor overlap of images becomes distracting and would be a deal killer. Maybe lower magnification and/or larger objective lenses would make it more forgiving of misalignment? Then I wondered how narrow they would go. The minimum eye spacing was checked on this pair and it’s 56.6mm while the specs say 58mm so there’s a chance the model you are interested in will go down a little further than the specs suggest. Hope that helps.

 

[timbernomad]

Yeah, I was wondering if 8x42s with a 57mm minimum IPD (I'm thinking the Athlon Midas in this case) could work for someone with a 56mm IPD. I was thinking maybe the larger exit pupil would make them work in spite of the difference.

 

[TaperPin]

Yeah, I was wondering if 8x42s with a 57mm minimum IPD (I'm thinking the Athlon Midas in this case) could work for someone with a 56mm IPD. I was thinking maybe the larger exit pupil would make them work in spite of the difference.

I see those are available on Amazon - if it didn’t work out the new paperless Amazon returns are very easy: Amazon gives you one of those square barcodes, go to a UPS store or other place that processes returns, they scan the bar code on your phone, print the return label and take the return. Easy peazy.

 

[Focus Knob]

You never know may be the optometrist got her IPD wrong +- 1mm. I even read that you can go to one optometrist and they give you a -1.25 prescription and then if you go to another optometrist they can give you a -1.5 prescription and it's still considered acceptable due to how the human eye compensates.

Also, a lot of lazy manufacturers will wrongly state the specs of their binoculars.

 

[Focus Knob]

The IPD also changes depending on if you're looking far or near. Like going crosseyed. For me when looking at a distance I sometimes spread the binoculars just a little instead of merging the two circles and it feels more comfortable. So I see the classic binocular silhouette instead of just a circle. Depends on the day.

 

[SikaSeeker]

Yes good point on accurate IPD measurement. The easy solution is of course to go to a shop and ask to try out binoculars or try a friends.

 

[LeonWang]

IPD is one of the most important specs. Leica ultravid are good for narrower IPD. Think of how you can experience black outs or kidney beans if you misplace your eye on some binos

Agree, it is super critical! Most time it will work fine with a slightly smaller distance than one's IPD, but not the other way around. It also depends on the focusing distance. The closer the focusing, the smaller distance it requires to merge the view. So for someone with an IPD of 56mm, it is better to have at least 1mm safety room and buy something with a minimum IPD of at most 55mm.