54mm interpupilary bins?

[dlleno]

Hello,

pardon my immediate intrusion into the equipment forum as a first post. I hope it is appropriate to ask for equipment advice here, but please direct me elsewhere as appropriate...

I am having difficulty finding a pair of binoculars that will fit my wife's 54mm interpupilary distance. Our interest is general wildlife observation, which includes birds of course, but to be honest we are not dedicated birders (we like bear and coyotes just as much...) . Accordingly, I suspect that a 10x would better suit long distance observation, for example in Yellowstone where we recently visited (where, incidently, we observed a wonderful pair of pelicans taking off from the river, which I photographed using a rented Canon 100-400 lens...) . However, I will admit that I have not purchased binoculars before; only used a pair Nikon 10x36 (sporter) while in the park.

Thus, we are attracted to the higher magnification to aid long distance viewing, but remain open to the experience of others, naturally. I'd go to 12x but suspect the shake factor would be too great, and suspect that as soon as I would try to follow a hawk, Heron, or falcon in flight I might wish for the smaller magnification? So you can see that we are after one binocular that will do everything.

But the 54mm constraint still comes into play. Incidently, my wife thought that the sporters were better than she has ever looked through before, but she is not experienced enough to know if the sporters optimally accomodated her eye separation or not. She's always reported problems with binos even when the eyepieces are adjusted as close as possible.

So far I have found only one pair of 10x binoculars, the Pentax DCF HRc in 10x43, that claims to accomodate a 54mm interpupilary distance. I've looked (online) at most all of the well-known brands disussed here and find that all except the above either do not specify the interpupilary distance adjustment range, or have a minimum pupil spacing of 56mm, 58 or even 60mm.

Yes we will go try some 56mm spacing binos, to see if they are "good enough". But I'd be interested in hearing from some of you experienced folks here on this topic.

many thanks,

Doug

[rivergazer]

I went through this recently because my girlfriend also measures 54mm, and can't comfortably use my original Stokes DLS with 57 (more like 57.5mm) IPD. I ended up with a pair of Nikon SE porros for $500, and she and I both love them. All of the SE series spec 53mm minimum I think, and they're all wonderful glass, but I'd stick to the 8 or 10 power myself. I don't know all the choices available with 54mm, but as I recall, most of the ones with narrow IPD are EXPENSIVE ONES!!!! I know through Steve at Optics4Birding that the Alpen Wings for about $400 have ED glass and narrow IPD, and, I discovered by email to Zen Optics, that their spec is 56mm, but someone on BF kindly measured his Zen ED's for me, and said his were 55mm. My girlfriend COULD get a round field with the Stokes 57.5mm, but it was really hard to stay centered, and not get blackouts. Though she measures 54mm, when she adjusts the Nikon SE's to her preference, it usually ends up about 55mm+ a little. Go figure. I think the less expensive model Zens have the same 55/56mm IPD. From posts on here, the Zen ED's are a real bargain at about $400, and the ZRS's are as well, at less than half of that.

marty

[Steve C]

Welcome. There are three relatively inexpensive porro prism glasses that pop immediately to mind. Inexpensive but optically stellar considering the price. The first is the Leupold Yosemite. Designed for kids and small stature adults. Comes in 6x and 8x30 and cost about $100. Will adjust to 50mm minimum IPD.

Just in the last week Vortex introduced their competition porro called the Raptor, It comes in 6.5x32 and 8.5x32. Same with the Eagle Optics Raven. Same binocular. They claim to adjust to 50 mm.

Look here ion the first page and you will find lots of comment on the Raven and some on the Raptor. There is more than an abundance of information on the Yosemite here as well.

I've got both Yosemite's and the 6.5 Raven. Both will give images equal to roof prisms costing 3x more. Good binoculars.

[Alexis Powell]

The IPD design issue (for people, mostly women and kids, who have an IPD less than the de facto industry standard of 56 mm) is one that I've been concerned with for a long time. You could do a search for other posts by me and including the word interpupillary for more of my specific thoughts and recommendations, but here is the lay of the land as I see it.

Pocket roof models (e.g. Zeiss 8x20 Victory, Leica 8x20 Ultravid) offer tiny IPD adjustments, but they aren't the sort of binos you're looking for.

Compact reverse porro models (e.g. Bushnell 7x26 Custom Compact, numerous 8x25 models) rarely adjust below 56 mm, though there are a few that go down to 54. Because of the small exit pupil, even 54 may not be ideal because the adjustment has to be perfect for viewing comfort.

Mid and full-sized roofs almost universally do not adjust below 56mm. A notable exception is Zeiss. Their Conquest and full-sized Victory FL models (e.g. 8x42, 10x42) adjust down to 54mm and the 2/3 sized Victory FL (8x32, 10x32) go down to 52mm (They are the class leaders for narrow IPD in premium roofs!).

There are (or at least were) quite a few 2/3 and full-sized porro prism style binos that adjust below 56mm, even many models that officially spec 56 as their lower limit. A few years ago, I could have recommended any number of them at different price points, but in recent years many porro models have been discontinued, especially those with fold-down (rather than the more "modern" twist-up) eyecups. Twist up eye-cups make the ocular assemblies much larger, which places a limit on how closely their optical centers can come together. Also, even when they can adjust to low IPD, the big ocular assemblies can be a problem depending on the shape/placement of one's nose (there is no room left between the oculars for folks with big high beaks). I've not kept up with current porro models to know which adjust below 56mm (other than the Leupold Yosemite, which make a point of advertising this spec), but my experience has been that the majority did, but that most current models don't. Some excellent past models that are sometimes still available include the Nikon 8x32, 10x42, 12x50 SE, and Nikon 8x30, 10x35 EII models, all of which adjust down to 51 or 52mm if memory serves). Other exceptionally good past models (of the 1990s) include the original Swift 8x42 and 10x42 Ultralite porros, and the similar Celestron Ultima porros of that time. You might be able to find one of these, or similar, on the used market.

A final comment: finding IPD specs is difficult. Astronomics/Christophers used to be a good resource because they publish the spec for every bino they sell, but their inventory is now very limited (and mostly limited to roof models), so their website is not as useful as it used to be. Most other sellers don't list IPD, but manufacturers do give IPD specs in their catalogs, most of which are available as PDF downloads on their websites.

--AP

[edz]

Nikon SE 12x50 53-73
Nikon SE 10x42 53-74
Leica Trinovid 10x42 rp 54-75
Nikon Monarch ATB10x42 Roof 55-74
Swift Ultralite 8x42 51-76
Nikon SE 8x32 53-73
Swift Storm King 7x50 54-81
Captain's Helmsman 7x50 55-73
Nikon ProStar 7x50 54-79
Leupold Yosemite 6x30 49-71

[Alexis Powell]

Nikon SE 12x50 53-73
Nikon SE 10x42 53-74
Leica Trinovid 10x42 rp 54-75
Nikon Monarch ATB10x42 Roof 55-74
Swift Ultralite 8x42 51-76
Nikon SE 8x32 53-73
Swift Storm King 7x50 54-81
Captain's Helmsman 7x50 55-73
Nikon ProStar 7x50 54-79
Leupold Yosemite 6x30 49-71

Is that really the Leica Trinovid (BA or BN) listed above, or is it the much older Leitz Trinovid?

The Swift Ultralite you've listed must be the 1990s porro model, right?

--AP

[dlleno]

Nikon SE 12x50 53-73
Nikon SE 10x42 53-74
Leica Trinovid 10x42 rp 54-75
Nikon Monarch ATB10x42 Roof 55-74


many thanks.
The SE does look attractive, even if expensive. a very respected bino, it appears, in many respects, even if beyond my initial pricing goals. It is not water/fog proof though?

I can't find the Leica Trinovid in 10s42 but the Trivovids in general are more than I can spend. Must be a mis-print on the monarch ATB they are listed at 56-72 on both B&H and Nikon sites, but perhaps I am not looking at the right model.

[dlleno]

AD thanks for the most informative historical overview, and essential recognition of the problem I am facing. I was wondering about those spec'd at 56 and whether they would be "good enough". However, my wife has had trouble with every bino she has looked through, and so suspect she will really appreciate ones that fit her and have good quality optics.

I just can't spend $1-2K; $600 is really pushing it, but frankly if the SE turns out to be the bell-ringer then it would be worth seeing the smile on her face, if she can notice and appreciate the optics.

Anyone have experience with the Pentax DCF HRc? and can someone comment on the lack of water/fog proof of the SE? As you can see I'm just trying to build a short list. Yes we will go try some 56s and compare.

[Kevin Purcell]

Nikon SE 12x50 53-73
Nikon SE 10x42 53-74
Leica Trinovid 10x42 rp 54-75
Nikon Monarch ATB10x42 Roof 55-74
Swift Ultralite 8x42 51-76
Nikon SE 8x32 53-73
Swift Storm King 7x50 54-81
Captain's Helmsman 7x50 55-73
Nikon ProStar 7x50 54-79
Leupold Yosemite 6x30 49-71

From edz's measurements?

For example, I checked the new old Monarch and the new Monarch X on the Nikon web site and they're all speced at 56 to 72mm IPD. So I wouldn't bet on them all going to 55mm.

http://www.nikon.com/products/sportoptics/lineup/binoculars/index.htm

The SEs are speced from 53−73mm.

The old non-waterproof Swift Ultralite 8x42 porro (I presume) was a decent birding bin too but you'd have to find it secondhand.

The recent Leica Trinovid 10x42 is 56 to 76mm IPD (from my notes).

So you are left with the

[dustyview]

You owe it to yourself to try the 6.5x Raptor (or Raven) and one of the Yosemites first, I think. Binoculars have progressed quite a bit in just the past couple of years and image quality of these low-cost porros is quite high (they're also waterproof). An SE would be nice, but also considerably more expensive and a bit harder to track down. If you are in the US you can try both from Eagle Optics and return one or both within 30 days, no questions asked and no penalty. I'd love to be able to recommend the E2 Custom Compact as it is great optically and size-wise, but my pair measures a real-world 58mm min. IPD.


AD thanks for the most informative historical overview, and essential recognition of the problem I am facing. I was wondering about those spec'd at 56 and whether they would be "good enough". However, my wife has had trouble with every bino she has looked through, and so suspect she will really appreciate ones that fit her and have good quality optics.

I just can't spend $1-2K; $600 is really pushing it, but frankly if the SE turns out to be the bell-ringer then it would be worth seeing the smile on her face, if she can notice and appreciate the optics.

Anyone have experience with the Pentax DCF HRc? and can someone comment on the lack of water/fog proof of the SE? As you can see I'm just trying to build a short list. Yes we will go try some 56s and compare.

[rivergazer]

Some here will remember that recently I went through an agonizing comparison involving 8X32 Nikon SE's. I'm a neophyte myself, and though no one wanted to hurt my feelings, I think everyone was saying to themselves "KEEP THE SE's, you FOOL!!!". After much coddling and handholding here on BF, I finally decided to keep the SE's, and now that I'm used to them, if they didn't exist, at least from what I gather on BF, I'd have to pay something a bit under or over $2K for something to match the view I get with them. Now I just can't live without them ... funky eyecups, cheapie strap, bag, & accessories, and a look that will prompt other uninitiated birders to think "sheeeesh, too bad the guy can't afford some better glass!", and all!! If you want to read the whole painful saga, it's here http://www.birdforum.net/showthread.php?t=145495

They solved the IPD problem for my beloved as well, and I'm as worried about the lack of weatherproofing as I am that lightning will hit me; I'll just be careful, and bet that will be enough. If the price tag is a bit too steep, the less expensive porros mentioned above would get my serious consideration, waterproof or not. Thanks again to all who participated; these won't be my last pair of bins, but it's hard to imagine ever giving them up.

marty

[edz]

I can't find the Leica Trinovid in 10s42 but the Trivovids in general are more than I can spend. Must be a mis-print on the monarch ATB they are listed at 56-72 on both B&H and Nikon sites, but perhaps I am not looking at the right model.

All the measures I posted were hand measured with calipers. No website specs.

edz

[Alexis Powell]

You owe it to yourself to try the 6.5x Raptor (or Raven) and one of the Yosemites first, I think. Binoculars have progressed quite a bit in just the past couple of years and image quality of these low-cost porros is quite high (they're also waterproof). An SE would be nice, but also considerably more expensive and a bit harder to track down. If you are in the US you can try both from Eagle Optics and return one or both within 30 days, no questions asked and no penalty.

This is good advice. Do try the 6x and 8x Yosemite and the Raven models. They are a good value, and maybe all you need. But don't pick them over the SE for their supposed waterproofing. They are waterproof under warranty (which is perhaps valuable) but no porro with external focus, or at least no cheap porro with external focus, is really waterproof. On the other hand, I know folks who use the SE in moderately rainy conditions without having any problems.

--AP

[dlleno]

Yesterday was an interesting exercise in correlating the numbers with real experience -- With her 54mm IPD in mind we went shopping.

We tried the Yosemites first, and put them back. Then tried various Nikons, followed by more Leupolds, Pentax, Vortex, and others, but kept going back to the nikons for the simple reason they worked and worked for her, and worked easier and better than any of the others. For her, its all about how easy it is to bring the binos to her eye and quickly adjust for best image without dark circles. proof of the pudding is in the eating, not in the recipe I guess.

The 8.5x56 is nice, but heavy and doesn't focus close. 10x56s are too heavy as well, and were not easy for her to dial in. But the 10x42 roof Monarch worked well, and is now at the top of our list now. Even the Pentax DCF, which looked best on paper (for IPD), was just not as easy for her to dial in. I wish I could afford the Nikon Premium roofs in 10x45 -- they are wonderful and she liked them too. But we will probably settle for the Monarch's and save $600 :D

I can only suggest that Nikons IPD may be generously spec'ed (as others have suggested with field measurements) and that there is some unknown correlation between what the optomotrist measures and how the bino fits. Of course, other details, such as the adjustable eye cups, eye relief itself, and how they felt on her face, were important. Yes, she wears glasses, and tried with and without them on. The Monarch 10x42 roof handled all scenarious best for her with the least amount of fidddling (as we traded binos back and forth in the store)

BTW one store (sportsman's warehouse) has a calibration/resolution chart up on their wall. Its in a great, slightly dark location behind a ceiling light, and really shows up a pair of good binos.

We also tried the Monarch X 10.5x 45. For double the price of the ATB I was expecting little wow factor, and they were bright, to be sure. Alas, However, the diopter adjustment was so tight that it was impossible to adjust without introducing enough shake to make the adjustment meaningless. I even wanted them to succeed but, unless the copy we tried was unusual, they are worse than the ATBs and very dissapointing -- all on account of the horrible diopter adjustment.

I will say this, however: If we end up with the 10x42 roof ATB's I will miss the easy, locking diopter adjustment mechanism of the 10x45 premiums, not to mention their brightness and clarity, especially off center...

[Steve C]

We tried the Yosemites first, and put them back.
...

Purely as a matter of curiosity, why did they not survive inspection?

[dlleno]

oh -- they just required more fiddle time for her, thats all. for me they worked, and I can agree with others here that they are impressive for the price. but my wife didn't like the way the adjustments worked to get a clear image. If she can't get it to work right within a few seconds she puts it back :-). I don't know why, but she just had a better time with the Nikons.

[dlleno]

does anyone know if the Zen ED's will go just as narrow (IPD) as a Nikon Monarch? I wonder if, knowing that the Monarchs work, if I should bring in an ED for her to try

[Steve C]

does anyone know if the Zen ED's will go just as narrow (IPD) as a Nikon Monarch? I wonder if, knowing that the Monarchs work, if I should bring in an ED for her to try

I've got both at home and will check after work. Right off the top of my head, I think they are about the same. I'm not sure about the new 7x36 ED 2, but keep those in mind. Also keep in mind the Monarch does not play in the same league as the ZEN ED.

The x43 ZEN ED is big. The x42 Monarch is much smaller and may be easier for her to hold. That is where the 7x36 may be better for your wife than the 8x43. The slower focus of the x43 ZEN might not be to her liking either, while the new faster focus of the ZEN ED 2 may be a significant improvement.

[rivergazer]

does anyone know if the Zen ED's will go just as narrow (IPD) as a Nikon Monarch? I wonder if, knowing that the Monarchs work, if I should bring in an ED for her to try

Zen's spec is 56mm, I believe, and one of the posters here measured his ED's (NOT ED2's but I'd assume they're the same) at 55mm. I don't know the spec on the Monarch (ATB?)

[dlleno]

yea both the Monarch lists min IPD at 56mm, so naturally I was astonished to see them stay out of the display case for very long. that made me wonder if either the optomotrist or Nikon were either wrong, use different measument technique, standard, tolerance, etc, and if something else like a Zen might work as well.

She does like the monarch 10x42 size. At 27 oz, the Zen's are almost a half pound heavier than the Monarchs tho...

[Kevin Purcell]

yea both the Monarch lists min IPD at 56mm, so naturally I was astonished to see them stay out of the display case for very long. that made me wonder if either the optomotrist or Nikon were either wrong, use different measument technique, standard, tolerance, etc, and if something else like a Zen might work as well.

Opticians are pretty good at getting the the IPD correct with a ruler and a "squint" and there are rather better tools (needed for progressive lenses) that can give each eye's IPD/2 to 0.5mm.

You can do the measurement at home too with a digital camera. Take a portrait shot with her eyes centered whilst she holds a ruler to her forehead. Then do the measurement from the photo -- measure from iris edge to the same iris edge across the center of the eyes (don't try to estimate the center).

Zen's spec is 56mm, I believe, and one of the posters here measured his ED's (NOT ED2's but I'd assume they're the same) at 55mm. I don't know the spec on the Monarch (ATB?)

I measured mine and get 57mm (just with a ruler). So I think you aren't going to see 54mm with the ZR ED (even if I'm measuring 1mm high).

For the Yosemite where was the problem? The only thing that struck me as a problem was a stiff diopter setting (a little "working" loosens it up).

Your wife might have to consider the trade off but if the Monarch works ...

[Steve C]

oh -- they just required more fiddle time for her, thats all. for me they worked, and I can agree with others here that they are impressive for the price. but my wife didn't like the way the adjustments worked to get a clear image. If she can't get it to work right within a few seconds she puts it back :-). I don't know why, but she just had a better time with the Nikons.

I wonder about this "get it to work right in a few seconds". Usually when one gets to where they are going and gets it set up before they start to use it (some settings can change going into and out of the case), the IPD and diopter setting should be spot on when the first bird is seen. Unless the focus is really quite loose, even the focus should be really close. At worst a bump of the focus wheel should be all that is needed. This may be a beginners use technique problem to some degree.

Put another way, even the diopter should not move even going into and out of the case. Once set, it should be pretty much a non issue. So it is get to the site, get the binocular out of the case, adjust the ipd, spot check the focus and head out. From there it is mostly a look and point thing, along with some use of the focus wheel.

[dlleno]

well when when she would take the binos from me (in the store) , all three things (eye cups, diopter, IPD) had to change, and she experimented with both "glasses on" and "glasses off" (she has a correction at infinity). If the ergonomics didn't agree with her right away and if she couldn't dial it in immediately she put them down. Only the 10x42 monarchs survived :D other monarchs didn't (8.5 x 56, 10 x 56, etc.). I had to give up concentrating on optics ...

She knows that in the field, she won't be the only one using them, so she needs the assurance that no matter who has them before, she can quickly get it back to her settings. Yea, not much patience for experimentation, thats true, God love her!

[rivergazer]

I measured mine and get 57mm (just with a ruler). So I think you aren't going to see 54mm with the ZR ED (even if I'm measuring 1mm high).

Zen spec is 56mm, one poster here says his are 55mm, another says 57mm. A non issue for most, but critical for others like Dlleno. My girlfriend has a similar condition. Can we find out if sample variation explains it (I hope not), or is it measuring differences.

marty

[dlleno]

This has to mfg tolerances and sample variation; I notice the same thing (one copy 57 the other 55). I've exchanged email with Charles at Zen who suspects that for whatever reason, if the Monarchs work the Zens may as well. I fully expect that we could have sampled a narrow Monarch and might get a wide Zen... I think its just normal distributions and standard deviations...

I can see that some of the larger lenses (like 56mm) can't possibly adjust down to even 56, but I can't see why the mfg adjustment stop has to be where it is, as long as it protects the lenses from banging together.

[rivergazer]

This has to mfg tolerances and sample variation; I notice the same thing (one copy 57 the other 55). I've exchanged email with Charles at Zen who suspects that for whatever reason, if the Monarchs work the Zens may as well. I fully expect that we could have sampled a narrow Monarch and might get a wide Zen... I think its just normal distributions and standard deviations...

I can see that some of the larger lenses (like 56mm) can't possibly adjust down to even 56, but I can't see why the mfg adjustment stop has to be where it is, as long as it protects the lenses from banging together.

I've never made binocular parts, but have been the guy operating the mill/lathe, etc., and, the guy doing the drawings and specs for lots of precision parts, and a 2mm variation in a hinge stop would be huge in my experience. If the rest of the mechanisms had tolerances that sloppy, there'd be ALL KINDS of problems. Maybe they do everything else with the necessary precision, and leave that hinge spec sloppy, but it's hard to imagine. BTW, the poster who measured 55mm on the Z ED's said that at minimum IPD, the barrels came to within the thickness of a piece of paper of touching at the objective end.

[Malcolm Stewart]

My IPD is quite wide, but I notice that if I'm focusing close objects, the comfortable IPD for viewing has to be set lower than for distant objects. Would this have a bearing on the above purchase decisions?

[Kevin Purcell]

My IPD is quite wide, but I notice that if I'm focusing close objects, the comfortable IPD for viewing has to be set lower than for distant objects. Would this have a bearing on the above purchase decisions?

This is normal (you toe-in your eyes to look at closer things). It would only cause a problem if you were close to the object and you were at the lower limit of the IPD for the bins already. In which case you'd loose some overlap.

e.g. I'm 65mm far IPD and 62mm close (reading) IPD ... the ratio is very similar for all people (it's just geometry!). So perhaps if you are less than 59mm IPD and you expect to do some 1m butterflying you might start to worry about the minimum IPD,assuming you are looking at the conventional 56mm minimum. With a 58.7mm IPD the 56mm IPD will work at reading distance (closer than the bins will focus).

But really this is only a problem if you are really close to the lower bound of the IPD.

And might be a consideration for the original poster too.

[rivergazer]

This is normal (you toe-in your eyes to look at closer things). It would only cause a problem if you were close to the object and you were at the lower limit of the IPD for the bins already. In which case you'd loose some overlap.

e.g. I'm 65mm far IPD and 62mm close (reading) IPD ... the ratio is very similar for all people (it's just geometry!). So perhaps if you are less than 59mm IPD and you expect to do some 1m butterflying you might start to worry about the minimum IPD,assuming you are looking at the conventional 56mm minimum. With a 58.7mm IPD the 56mm IPD will work at reading distance (closer than the bins will focus).

But really this is only a problem if you are really close to the lower bound of the IPD.

And might be a consideration for the original poster too.

I'm lost on this one. I can understand the toe-in with naked eye when viewing close objects, but with any binocular, even if the object is very close, at the close focus limit of the bin (18" in some cases), it seems that what you're viewing is not the object, but the image(s) in the exit pupils of the bins, which I'd think would remain at a fixed distance apart, no matter what the distance the object is from the viewer. My Stokes DLS close focus at 4.5 feet, and when viewing objects near the limit, I do get a bit of the "hollywood movie" overlapping circle thing, but moving the IPD inward just moves the circles closer.

[henry link]

I'm lost on this one. I can understand the toe-in with naked eye when viewing close objects, but with any binocular, even if the object is very close, at the close focus limit of the bin (18" in some cases), it seems that what you're viewing is not the object, but the image(s) in the exit pupils of the bins, which I'd think would remain at a fixed distance apart, no matter what the distance the object is from the viewer. My Stokes DLS close focus at 4.5 feet, and when viewing objects near the limit, I do get a bit of the "hollywood movie" overlapping circle thing, but moving the IPD inward just moves the circles closer.

Your eyes are forced to toe in at close distances with binoculars for the same reason they toe in naked eye for reading. The height of the triangle formed by the eyes and the object gets progressively shorter. But, toe-in of the eyes is required at a longer distance with binoculars both from magnification and, in the case of traditional Porros a baseline between objectives that is wider than the baseline of the eyes. The "hollywood movie" separation of fields occurs because the binocular optical axes are parallel and nearly fixed in separation distance (except for the Papilios) If you look at each field separately you will see that a close object cannot be centered in both the right and left fields simultaneously. We tend to place close objects in the center of the overlapping area between the fields, which means the object is viewed off-axis in both fields. How far off-axis depends on distance, objective spacing and magnification. Wide objective spacing and high magnification cause the object to move further off axis in each side forcing the eyes to toe in more to center the object in a smaller area of overlap. In a binocular with less than stellar off-axis sharpness this can easily place a close object outside the sweet spot in both fields. Because of this parallax effect traditional Porros are at a disadvantage for close in birding below 20-30 feet compared to roof or reverse Porro. I have an extreme example of what results from wide objective spacing and high magnification in the Nikon 8-16x40 zoom Porro binocular. At 16x the field is only about 3.4 degrees. At 12 feet a "centered" object is at the right edge of the left field and the left edge of the right field.

[Howard220]

Thanks, Henry. That confirms what I suspected about porros vs. roofs. I use primarily a reverse porro, and have little trouble viewing things up close. I suffer from a lazy eye, and it can be quite strain for me to pull two images together in standard porros, of which I own two for birding. It looks like there will [have to] be a nice roof in my future!

[rivergazer]

Henry,

After I read your post 50 more times I'll be a much smarter man

thanks,

marty

[dlleno]

ditto from me. Henry that was a most informative post.

[dlleno]

This is normal (you toe-in your eyes to look at closer things). It would only cause a problem if you were close to the object and you were at the lower limit of the IPD for the bins already. In which case you'd loose some overlap.

e.g. I'm 65mm far IPD and 62mm close (reading) IPD ... the ratio is very similar for all people (it's just geometry!). So perhaps if you are less than 59mm IPD and you expect to do some 1m butterflying you might start to worry about the minimum IPD,assuming you are looking at the conventional 56mm minimum. With a 58.7mm IPD the 56mm IPD will work at reading distance (closer than the bins will focus).


Just for grins, I confirmed with my wife's eye doctor that her 54mm IPD was measured during "distance" viewing. They confirmed the 3mm generalization as well, for reading distances (e.g. 20 inches).

But I also learned that most eyes IPD will naturally adjust/accomodate up to +/- 1mm (each) even during distance viewing. So the combination of this factor, plus the mfg tolerances of the monarchs themselves may help explain why my wife is able to use them.

[Pileatus]

Your eyes are forced to toe in at close distances with binoculars for the same reason they toe in naked eye for reading. The height of the triangle formed by the eyes and the object gets progressively shorter. But, toe-in of the eyes is required at a longer distance with binoculars both from magnification and, in the case of traditional Porros a baseline between objectives that is wider than the baseline of the eyes. The "hollywood movie" separation of fields occurs because the binocular optical axes are parallel and nearly fixed in separation distance (except for the Papilios) If you look at each field separately you will see that a close object cannot be centered in both the right and left fields simultaneously. We tend to place close objects in the center of the overlapping area between the fields, which means the object is viewed off-axis in both fields. How far off-axis depends on distance, objective spacing and magnification. Wide objective spacing and high magnification cause the object to move further off axis in each side forcing the eyes to toe in more to center the object in a smaller area of overlap. In a binocular with less than stellar off-axis sharpness this can easily place a close object outside the sweet spot in both fields. Because of this parallax effect traditional Porros are at a disadvantage for close in birding below 20-30 feet compared to roof or reverse Porro. I have an extreme example of what results from wide objective spacing and high magnification in the Nikon 8-16x40 zoom Porro binocular. At 16x the field is only about 3.4 degrees. At 12 feet a "centered" object is at the right edge of the left field and the left edge of the right field.
Henry,

My SE 8X32 porro is perfect up to its minimum...about 9 feet. My Leica roof is not as pleasing at close distances. It all depends on your personal IPD and, more importantly, the size of the binocular's "sweet spot". I smile whenever I read that porros lose to roofs at close distances. It just isn't universally true.

John

[henry link]

John,

Yes, the 8x32 SE works at short distances better than most Porros. It can tolerate a large displacement of an object away from the center because of the unusually generous sweet spot, but I still don' t like it at short distances because the large displacement requires so much eye toe-in that the exit pupils are partially blocked. To get a reasonably clear aperture I have to reduce the IPD by about 4mm compared to the normal long distance setting. So, I agree it works well for the type, but it would work better if the objectives were closer.

Henry

[rivergazer]

Charles at Zen tells me that the minimum IPD on the 7X36 ED2 is 54-55mm, a bit less than it's bigger brothers, but cannot go lower due to the size of the oculars. Also, it's a bit shorter, at 5.8" long.

[Alexis Powell]

Hey, that's cool about the Zen Ray 7x36 ED2 being speced for <56mm minimum IPD. I hadn't visited the Zen Ray website before except to order the 7x36, but I just noticed that they claim a 52mm minimum IPD for their reverse-porro compact, the 8x26 Vista. It also has good FOV and eye-relief spec. Except for the 13 foot close focus, that makes this a very attractive choice for kids. With current 20% off coupon, it is $60. I'm not sure I've ever met a $65+ reverse-porro compact that I didn't like (though I've also yet to fall in love with one) but I'd be interested to learn more about this one. Has anyone tried it?

--AP