Binocular "Fit"-Interpupillary Distance (IPD) (1 Viewer)

[David in NC]

Guess I need to know mine(?)

As many of you know (and are probably tired of reading) I'm hoping to buy a new pair of bins soon.

I agree with something I've read over and over here and on other forums that "fit" may trump optical performance when it comes to selecting a pair of binocs.

I have noticed that I often have a hard time adjusting bins down to my IPD, but depending on the model, this isn't "all the way closed"; I still feel like I'm on the narrow side of male IPD though (?)

Usually the problem is with porros, but even some roofs (and small ones at that) are hard for me to close together small enough to get the "perfect" round image we seek while using bins (sometimes getting the finicky shadows or semi-circles ghosting in on the sides with almost no movement).

Since I'm talking about buying my most expensive pair to date, I'm really stressing about this... :-C

I have mentioned this before, but I once purchased a set of 8x32 Victory FLs and couldn't get them set for my eyes. What bothers me here is these were supposedly rated for 52 mm and up (52 being the narrowest of about any I've seen.)

The easiest/best view I've ever had was a set of older Swarovski SLC 8x30s, but I can't for the life of me find specs for these.

My wishlist only contains 3 or 4 that have a 54 or less IPD so this may help narrow my choices, IF this is as important as I'm starting to think...

Thoughts on IPD and "fit"???

 

[SteveTS]

I'm really stressing about this... :-C

David,

Time for an eye-test ; your optician or optometrist will be able to measure this for you, along with your 'exit' pupil, and a good scan of your retina, all useful !

 

[OPTIC_NUT]

At 50mm, you have a special requirement, outside most models.
And...you've got to get that right.


The www.bhphotovideo.com site has a lot of neatly organized technical info.
I can see the Leupold Yosemites go to 50mm IPD, but they are lower price range.
Still, surprisingly great view.

In the smaller sizes, you can get double-hinged roof binocs in an Alpha name.
The Leica 8x20 Ultravid covers 34-74mm, for example:
http://www.bhphotovideo.com/c/product/1008407-REG/leica_40628_8x20_ultravid_colorline_binocular.html

I checked the Nikon Premiers....a bit depressing: they don't go to 50mm IPD.


The Swarovski 8x25 CLs go to your IPD:
http://www.bhphotovideo.com/c/product/994400-REG/swarovski_46200_8x25_cl_pocket_binocular.html


There are other double-hinge 8x25s at lower prices.
Not guarantee a model will make 50mm, though, so you'd
better make sure in print first.

 

[FrankD]

David,

I think I understand what you are referring to but I wonder if it is more than just IPD. As most people often do I try to put myself in your shoes and relate it to my own experiences. Is this just the case of the oculars not getting close enough together or is it a combination of that and eye relief?

Case in point, and one that I have mentioned previously in other threads, I owned a pair of Nikon E II 8x30s for some time. I tried to get along with them but I couldn't get the IPD down to a low enough setting without having the eyecups pinch my nose. In other words the eyecup diameter was too large for the shorter level of eye relief that they exhibit. I either got extreme tunnel vision as my eyes were too far from the ocular surface or I couldn't get proper image overlap because I couldn't get the IPD narrow enough because of my nose.

On the other hand, I own one model that has 12 mm of usable eye relief and have used another that has even less than that. I don't have a problem seeing the full field of view in either (I don't wear glasses) because the eyecup diameter is narrow enough to get past the bridge of my nose.

Again, this is me just wondering if your situation is strictly needing a narrow IPD or if there is more to it than that.

 

[Kammerdiner]

I think Frank may be onto something. In a study of 1771 males the minimum IPD was 52mm, but even the 1st percentile was 57mm. 50th percentile was 65mm.

The Zeiss 8x32 FL does indeed go down to 52mm.

Here's the study results:

http://en.wikipedia.org/wiki/Interpupillary_distance

If you have a pair of binoculars that work well for you, set the IPD at infinity and measure from the outside of one cup (or the eyepiece itself) to the inside of the other. It'll be quite accurate, especially if the bino has a smaller exit pupil. Then you'll have a better idea what's going on.

Mark

 

[OPTIC_NUT]

Good idea.
Or, if there isn't a pair in the range, buy a dumpy double hinge pair and use that
(for just that purpose). The Tasco 10x25s at the WalMart are $10 and have
a "sweet spot" of only 30-40% of the field. It's appalling. The rest is abstract painting.
However, all the better for centering your eyes ...and then whipping out the ruler.

 

[David in NC]

I think a couple of you are onto something...

A very UNSCIENTIFIC attempt at measuring IPD results in a measurement of 60-61 mm. More to human specs! Probably an eyecup issue then (?)

Are there other factors involving the eyes? I know that on some (most?) the pupil's maximum opening size begins to decrease as we age...but anything else?

I'm male, 47, large build, and have excellent eyesight from arm's length out (once tested at 20-10, now more like an average 20-20) but find myself using reading glasses for close up stuff.

 

[elkcub]

...
The easiest/best view I've ever had was a set of older Swarovski SLC 8x30s, but I can't for the life of me find specs for these.
...

Hi David,

I have several Swarovski catalogs dating back to 1994. The IPD range for the 8x30 SLC was consistently 56-72mm, with an ER = 15mm (in later catalogs). This would appear to be inconsistent with your 52mm IPD requirement, so indeed something else is probably involved.

Ed

 

[David in NC]

David,

I think I understand what you are referring to but I wonder if it is more than just IPD. As most people often do I try to put myself in your shoes and relate it to my own experiences. Is this just the case of the oculars not getting close enough together or is it a combination of that and eye relief?

Case in point, and one that I have mentioned previously in other threads, I owned a pair of Nikon E II 8x30s for some time. I tried to get along with them but I couldn't get the IPD down to a low enough setting without having the eyecups pinch my nose. In other words the eyecup diameter was too large for the shorter level of eye relief that they exhibit. I either got extreme tunnel vision as my eyes were too far from the ocular surface or I couldn't get proper image overlap because I couldn't get the IPD narrow enough because of my nose.

On the other hand, I own one model that has 12 mm of usable eye relief and have used another that has even less than that. I don't have a problem seeing the full field of view in either (I don't wear glasses) because the eyecup diameter is narrow enough to get past the bridge of my nose.

Again, this is me just wondering if your situation is strictly needing a narrow IPD or if there is more to it than that.

May be it...I know I do try to press oculars CLOSE to hide any light coming in from the side. In fact I prefer winged eyecups and ran those on my last "main" pair (A Vortex first generation Razor 8x42). So...I may be bringing non-winged eyecups back against my face.

I too can easily use bins with a short eye relief. One I liked and my wife didn't (glasses wearer) had 13mm I think...

 

[David in NC]

Hi David,

I have several Swarovski catalogs dating back to 1994. The IPD range for the 8x30 SLC was consistently 56-72mm, with an ER = 15mm (in later catalogs). This would appear to be inconsistent with your 52mm IPD requirement, so indeed something else is probably involved.

Ed

Thanks for looking that up elkcub. That helps to reassure me. I HATE I sold that binocular! :C If a midlevel bin was that good in the 90s, I can only imagine how good a Swarovision EL must be!

 

[elkcub]

... I have noticed that I often have a hard time adjusting bins down to my IPD, but depending on the model, this isn't "all the way closed"; I still feel like I'm on the narrow side of male IPD though (?)

Usually the problem is with porros, but even some roofs (and small ones at that) are hard for me to close together small enough to get the "perfect" round image we seek while using bins (sometimes getting the finicky shadows or semi-circles ghosting in on the sides with almost no movement).

Since I'm talking about buying my most expensive pair to date, I'm really stressing about this...

David,

I don't know how much experience you have using binoculars, and please don't take offense, but the problem may be that you're going in the wrong direction by moving the eyepieces too close together. (Perhaps that's because you believe that you have a really narrow IPD?)

In any event, if you're doing that what you will see is a fairly crisp circle with "ghosting" on one side. That's because you're really only viewing with one eye; the ghosting appears on the nasal side corresponding to the eye getting little or no image.

Ed

 

[Steve C]

Like Frank, I try to put myself in your place. But I can't quite come to grips with what you describe. The first thing I thought is along the lines there is no way to fit a nose between human eye sockets with an adult with 50 mm IPD, that can't be right.

Like Ed said, are you sure of the way you set the IPD? Again, and don't take offense here either, you do realize that eye glass wearers have the eye cup in and non eye glass wearers out B ? I've sat at optics booths is shows before and trust me, that is not a given bit of knowledge. Sometimes we need to get the simple stuff down.

It could be you need a smaller than typical eye cup diameter to fit with you face and eye socket conformation, so be sure to look at some 30-32 mm stuff and see.

I have a notion that there is something pretty simple fouling up some basic human/binocular alignment issues.

Since the Swarovski 8x30 SLC worked, I'd go back there. Not necessarily to Swarovski, but to 30-32 for searching for your glass . Don't think that 8x30 SLC was ever considered mid level either. Wider eye cups from a binocular with field flattener lenses might not work either. Anyway I have an idea it may be an eye cup diameter issue.

 

[David in NC]

David,

I don't know how much experience you have using binoculars, and please don't take offense, but the problem may be that you're going in the wrong direction by moving the eyepieces too close together. (Perhaps that's because you believe that you have a really narrow IPD?)

In any event, if you're doing that what you will see is a fairly crisp circle with "ghosting" on one side. That's because you're really only viewing with one eye; the ghosting appears on the nasal side corresponding to the eye getting little or no image.

Ed

I move them until I get the closest thing to perfect image overlap, using the entire range of adjustment available. I was just shocked and disappointed I couldn't get on with the 8x32FLs, considered a "grail" bin by some. Maybe my eyes like larger exit pupils for ease of view...?

 

[David in NC]

Like Frank, I try to put myself in your place. But I can't quite come to grips with what you describe. The first thing I thought is along the lines there is no way to fit a nose between human eye sockets with an adult with 50 mm IPD, that can't be right.

Like Ed said, are you sure of the way you set the IPD? Again, and don't take offense here either, you do realize that eye glass wearers have the eye cup in and non eye glass wearers out B ? I've sat at optics booths is shows before and trust me, that is not a given bit of knowledge. Sometimes we need to get the simple stuff down.

It could be you need a smaller than typical eye cup diameter to fit with you face and eye socket conformation, so be sure to look at some 30-32 mm stuff and see.

I have a notion that there is something pretty simple fouling up some basic human/binocular alignment issues.

Since the Swarovski 8x30 SLC worked, I'd go back there. Not necessarily to Swarovski, but to 30-32 for searching for your glass . Don't think that 8x30 SLC was ever considered mid level either. Wider eye cups from a binocular with field flattener lenses might not work either. Anyway I have an idea it may be an eye cup diameter issue.

Seems logical to set the "hinge" to the best image overlap (one image)... That's what I do. The reason I started this thread was I was using my Vortex Viper HD 6x32 yesterday and noticed it was very hard to get a good perfect overlap (which I hadn't noticed before.) Maybe I didn't "fiddle" with them long enough...

And yes...before anyone asks... I know the IPD setting can change during handling/use/storage. I moved it back to a fairly comfortable view as soon as I picked it up and started watching some feeders.

On the matter of the 8x32FL, I kept it for the entire period until I couldn't return it (30 days?) and adjusted IPD, and eye cups up and down hoping to find the perfect spot. And yes I do realize that in general, eye cups are all the way out for non-eyeglass wearers.

Perhaps I could have stated in my first post "I pull the EYECUPS back into my eyes to block out distracting side light..."

Again, maybe I just need/prefer larger EPs... I am a permanent night shift worker (a true "NIGHT OWL")...

 

[Kammerdiner]

I move them until I get the closest thing to perfect image overlap, using the entire range of adjustment available. I was just shocked and disappointed I couldn't get on with the 8x32FLs, considered a "grail" bin by some. Maybe my eyes like larger exit pupils for ease of view...?

You may be onto something, I think. I was rather surprised to find the 8x32 SV so much more "eye friendly" than the 8x32 FL, which always seemed a bit fussy.

Here's a simple test. Hold the binos about a foot away with a bright exit pupil showing. Then slowly tip them to one side or the other and watch the exit pupils. The FL starts to compress laterally real quick (turns into a vertical eye shape) and gets worse till it blinks out. The SV stays a nice circle all the way out until it blinks out. I think that's "ease of view." Your eye doesn't have to be perfectly placed and you still get the full exit pupil. I don't know how they do it, but it does seem to work.

Mark

 

[David in NC]

You may be onto something, I think. I was rather surprised to find the 8x32 SV so much more "eye friendly" than the 8x32 FL, which always seemed a bit fussy.

Here's a simple test. Hold the binos about a foot away with a bright exit pupil showing. Then slowly tip them to one side or the other and watch the exit pupils. The FL starts to compress laterally real quick (turns into a vertical eye shape) and gets worse till it blinks out. The SV stays a nice circle all the way out until it blinks out. I think that's "ease of view." Your eye doesn't have to be perfectly placed and you still get the full exit pupil. I don't know how they do it, but it does seem to work.

Mark

You know you might start a poopstorm with comments like that...! o I felt I was bordering on heresy when I first mentioned it...and I WANTED to like the Zeiss!

This could be true because I know everyone mentions the "easy view' of the 8x32 SV...

 

[OPTIC_NUT]

Are there other factors involving the eyes? I know that on some (most?) the pupil's maximum opening size begins to decrease as we age...but anything else?

Well, you can have trouble finding a good place for your eyes without
"blackouts" for many binoculars...if you are nearsighted and using the
binocs without glasses. Either getting long eye relief and using
glasses, or clapping some correction over the ocular will fix that.

61mm IPD and shortsighted we can deal with.

 

[David in NC]

UPDATE-

Had an eye exam today...

They didn't nail down a single number for IPD-they used a Distance and Near number, and spoke of convergance... My Near was 63mm and the Distance was 66mm.

Okay (folks smarter than me) which would be my "IPD" for binocular usage? I'm thinking "Distance" but I may be wrong...or...would it be exactly in the middle of these numbers???

Also I am proud to say I still checked 20-15 in both eyes :king: except that they did confirm a mild (1.50) correction needed in near vision (which I knew-I use reading glasses at night).

 

[OPTIC_NUT]

You would go with the distance number. (66)
Most binoculars should easily work for you.
There might be some other issue between you and the FL's.
At the shop, I found the focuser jumpy-fast, so it was hard to get things sharp quickly.

 

[elkcub]

Hi David,

Since the eyes must "converge" to focus on near targets (perhaps down to a distance of 18," or so), it makes perfect sense that your IPD (inter-pupil distance) would become somewhat smaller, in your case by 3mm. However, your distance IPD (actually, slightly wider that the male population mean of 65) is the one you should use to set the binoculars for normal viewing. Only bring them closer together for very close observation (if you use two eyes).

The reason for this is that your eyes have little or no tolerance for "divergence." Hence, if your set them narrower you will experience eye-strain at typical distance viewing. My suggestion is to physically measure the IPD and mark the binoculars for future reference. Don't rely on getting a clear circle until you know more about what the proper setup should look like.

Ed