What’s the use of extra wide FOV (if you can’t see it) (1 Viewer)

Over the years I’ve come to appreciate binoculars, from the beautiful (and closer!) image they can provide of birds to the facts about the way they work, the differences between models, formats, brands or even the mere “feel factor” in the hand (I'm sure many forum members will share the same fascination).

Some things are more important for me than others (just like for everybody else I guess). I tend to like a wide field of view, but then… Some time ago I bought a classic 7x35 13º extra wide field binocular (it was a Japanese JB 146, if I remember correctly). The much anticipated view through them left me a bit cold (to say the least), I just couldn’t use the monstrous FOV simply because there was a certain point where my eyeballs were literally touching the glass on the eyepieces long before I could even reach to see the field stop. That left me thinking; I did the same test with the 8x30 EII (and it’s more than respectable 8,8º and I got a similar result; even with the eyecups folded down there was no way I could see the field stop (and thus make use of the entire 8,8º FOV). Well, then I forgot about that and lived happily ever after.

Last week I saw Minolta 7x35 Standard MK 11º (a binocular I’ve been very curious about for quite a while, after having read good critics both here and also in Cloudy Nights). I won’t go into detail about the optical performance of the Minolta (nor am I skilled to give anything but a personal experience). The Minolta looks more user friendly than the old JB-146, so I assumed it could show more of the promised 11º FOV. However, the experience let me down again. So I devised a simple test to see how much FOV I can actually see from a series of wide field binoculars (and other binoculars I have at hand): Minolta Standard MK 7x35 11º, Nikon EII 8x30 8,8º, Celestron Granite ED 7x33 9,1º, Nikon Monarch 7 8x30 8,3º, Kowa BDXD 8x32 7,5º.

NB* This is a COMPLETELY UNSCIENTIFIC test not to be taken too seriously. Nothing more than a excuse to spark conversation and learn more in the process. I have a good eyesight and have never used reading/prescription glasses. At 45 I still have a quite acute eyesight. I tend to use the eyecups all the way up on my binoculars, with some exceptions, where I can go down by one point, like in the 8x32 Zeiss Victory FL or the 8x30 Nikon Monarch 7 8x30. When I want to enjoy a huge FOV I usually twist them down for the sheer pleasure of the experience.

I have put on a tripod the mentioned binoculars and selected a landmark on the right hand side extreme (the side of a building in cream colour, marked with a black vertical line). As I tried all the binoculars, I placed the selected landmark always on the very edge at the right of my view, "the rightmost” point I could see without “hoovering” above the eyepiece, simply by looking “naturally” at the image in front of my eyes. Comparing my results with care I have noted the landmark I could see on the left most point of the FOV for every binocular. I have used a different colour for each binocular, and I have marked the limit of what I could see with the eyecups all the way up (l) and folded/twisted down (i). You can check the image while reading the results for a “full experience” Let’s go:

Minolta Standard MK 7x35 11º. Yellow line. With eyecups up the feeling is of very strong vignetting and a bit of a “looking through a pipe”, quite disappointing actually. Folding the eyecups down increases the experience, but you get the feeling that there is so much more FOV there that you will never be able to enjoy. The view is pretty uncomfortable, since you have to brush your eyelashes against the eyepiece in order to get a wide FOV. If I lean towards the sides (a lot) I can get to see the field stop, really hidden away, but if I do this and get a glance of the field stop the image I can see is an unusable crescent.

Nikon EII 8x30 8,8º. Red line. Quite surprisingly, with eyecups up I can see nearly everything I can see with the Minolta with folded eyecups (this is a revelation), and obviously the viewing experience is so much more relaxed and pleasant. Eyecups down and I can see way more than I get with the Minolta. However, the difference between eyecups up and down is nowhere near as big as in the Minolta.

Enter a contemporary roof, the Celestron Granite ED 7x33 9,1º. Light blue line. the only porro contender in the super wide field fight. Surprise, surprise, eyecups all the way up I can see so much more than with any of the previous contenders. Actually, I can see a tad more than with the EII with folded eyecups (another revelation). Again, I am not judging optical performance at the field or sweet spot, I’m only talking about how much FOV I can see today with my eyes trying to be as neutral as I can. I fold down the eyecups and the width of the field is magnificent. For the first time, I can see the field stop on both sides, so I’m making use of all the FOV the device is able to provide.

The underdog: Nikon Monarch 7 8x30. Green line. At 8,3º these should pose no threat to the previous specialists in wide FOV, or should it? Well, I was in for a big surprise: eyecups all the way up, I can nearly see the field stop and the very relaxed view leaves me very close to the EII. Eyecups down and I can see the field stop, the width does not match that of the EII. In this case, the difference between having the eyecups up or down is pretty narrow.

Wildcard: Kowa BDXD 8x32 7,5º. Dark blue line. With an AFOV of 56,5º these seem out of place in this test, but let’s see what happened. With a “limited” 7,5º I can see the field stop if I try hard, even with eyecups up, but again, the goal of this test is to measure what I can see looking in a “natural and relaxed way” through the binoculars. To my surprise, measuring the landmarks on the skyline of the town San Antonio (Ibiza), I can actually see the same FOV than with the Minolta with eyecups up. I twist the eyecups down and there’s hardly any difference, I can clearly see the field stop and maybe enjoy a tiny little more width of field.

So, to my surprise, the only roof (Celestron at 9,1º) provided the widest and easiest to obtain FOV and the obvious favourite (the Minolta at 11º) was defeated without mercy even by a small and “humle” roof (the M7) with its modest 8,3º and unexpectedly matched by a 7,5º small roof. All the three roofs showed their field stops more easily than the porros. Does anyone know if this is something typical of roofs because of the nature of their construction? Or was it simply the selected devices?

Any comments or ideas are more than welcome.

Whoa .....

Yarrellii,

There are considerations as to how much of the field of view is 'sharply' in view (the rest being our peripheral vision), but it seems to me that what you are mostly talking about is Eye Relief.

At the correct ER setting you should be able to see the full Fov. Obviously if your eyeballs are hitting the ocular lens before this happens then the ER is too short even for your naked eye ! :eek!:

13* in a 7x bin is a whopping 91* AFov. True field is 231m @1km.

Just a tip - if you measure your viewable field (as in your photo) over a known distance (a football field is good for this with 100m distance) then your measured results can not only be ranked relative to one another (the only thing possible in your photo) , but also compared to the stated field.

It doesn't give an exact figure because it doesn't take account of distortions, but just take the tan of the claimed Fov angle and multiply by 1000 to give the field width in metres at a distance of 1km. Similarly (as it is just using similar triangles) just multiply by 100 for the Fov width at 100m, or even by 10 to get the Fov width at 10m - you can use a regular builder's tape measure for this.

For example: tan(13*) = 0.231
Multiply by 1000 gives an Fov of 231m @1km
Multiply by 100 gives an Fov of 23.1m @100m
Multiply by 10 gives an Fov of 2.31m @10m

Quite apart from all of that, field quality comes into it. When I had my Swift Audubon 8.5x44 ED Porro's with 8.2* Fov (69.7* AFov), apart from the difficulties I had with lack of ER with my glasses on and not being able to easily see the field stop, the field curvature was so great at the edge that the last part of it was blurry (could be refocused). What this meant in practice was that a bird could be sitting in that blurry zone at the edge of the field and unless it moved you wouldn't know it was there.

I'd be interested to know the actual measured fields you can see with all those bins, but you will also need to include information on how close you got to the proper ER, as well as field quality. Many times I curse having to wear glasses to see (short sighted) , but the converse of that is that on some short ER bins where I trial them without glasses just for the heck and experience of it, I find my eyelashes contacting either the ocular lens or eyecup inners which is very disconcerting to me ! I have heard of some people trimming their eyelashes to get closer but I'm not going that far ! :eek!:





Chosun :gh:

Interesting 'real world' experiment. Your results with the Minolta make me wonder if earlier widefield designers did not necessarily intend that you should see the entire field stop at all times. In other words, if your pupil is at the maximum aperture (5mm for a 7x35) then maybe the field stop is visible at the correct eye relief, but at 3mm in bright daylight, it may not be. That would also have the convenient benefit of hiding the less corrected edge of the field from the viewer most of the time.

-Bill

yarrellii said:

The much anticipated view through them left me a bit cold (to say the least),

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About two years ago at SHOT Show, I looked through a prototype of an "extremely wide FOV binoculars". I didn't feel any WOW feeling, it felt like a normal premium binoculars.

In agreement with your observations, it has also been my experience that once you get past tunnel-vision level, making FOV extra large doesn't really help. An apparent FOV of about 60 to 65 degree is enough. More than that creates sever ergonomic problems: large FOV must be accompanied with longer eye relief to allow for the center of rotation of your eye to be positioned at the exit pupil. This is in contrast to normal straight viewing where the entrance pupil of the eye is positioned at the exit pupil. Once you make the eye relief longer, then you need really large eyepiece lenses. Then their inner edges could hit your nose. So, the "traditional model" of providing wider FOV by increasing the FOV of each individual eyepiece is not very efficient.

I am following a different approach to increasing the FOV of binoculars: making their stereoscopic field of view larger than their monoscopic (is that a word?) field of view. See the thread called New Horizons II

Yarelli,
I took the liberty of scaling your photo to match a grid, and used the view of the Celestron and Kowa as a reasonable measure of degrees, since you could see the entire field with those. As you could see more than the field with the cups down, I assume that is black, so the eyecups 'up' on the Kowa and Celestron are lined up with their stated fields. Certainly not 'accurate' either, but it does show a reasonable correlation across all the bins.

It does make me wonder what the Minolta was designed to do, since viewing it without glasses only gives you, at most about 8.8°. The design leaves more than 2° hidden from the viewer, unless whats out of view is unusable anyways...

Is it just marketing and bragging rights from another era? 11°! Widefield!

-Bill

Chosun Juan said:

Just a tip - if you measure your viewable field (as in your photo) over a known distance (a football field is good for this with 100m distance) then your measured results can not only be ranked relative to one another (the only thing possible in your photo) , but also compared to the stated field.

It doesn't give an exact figure because it doesn't take account of distortions, but just take the tan of the claimed Fov angle and multiply by 1000 to give the field width in metres at a distance of 1km.

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Chosun. Wow! I think I had to read your comment at least 3 times before I could try to understand the logic behind. Not your fault, I'm a mess when it comes to maths and geometry (I studied Humanities!). However, I think I you might have taken my aim too seriously (or my skills to highly!). The little test was just a simple game to show what I can see through different binoculars, and the relationship with their claimed FOV (and the conclusions or discussions derived from the results).

As a general note, I don't wear glasses, so I've never used binoculars with them (I assumed, I don't know if incorrectly, that without glasses you are generally speaking in a "easier" starting point to enjoy full FOVs). Sometimes I try to mimmic the experience of using glasses (just to try and get a feeling of what that might be like) by using the binoculars with my sunglasses on, and the result is quite disappointing. I guess sunglasses are not meant to have good bino-using performance.

Anyway, back to the topic. I'm very interested in your bit that says "At the correct ER setting you should be able to see the full Fov". Is that a expression of desire/wishful-thinking or is it the way it should be? (I'm asking from the humble standing point of plain ignorance, no second intention intended). If this is the case, I'm not sure if it is just me and my eyeballs, or there's something wrong with superwideFOV binoculars. Take the 8x30 EII, for example. There's no way I can see the field stop without leaning sideways, even with the eyecups fully down and my eyelashes brushing the eyepieces (let alone with eyecups up). And I don't even want to start talking about what happens when I try to look for the field stop in the 11º FOV Minolta. I have to lean sideways so much, that I simply loose the "roundness" of the image and by the time I see the sharp field stop I see little more than a crescent of image (find attached a "dramatization" that shows more or less what happens).
I am aware that there are many EII 8x30 users among forum members. It will be interesting to know how many (if any) actually see the sharp field stop when using their binoculars "naturally" (without hoovering or leaning sideways, so to speak).

Always interesting to read your comments, really informative and enlightening

wdc said:

Your results with the Minolta make me wonder if earlier widefield designers did not necessarily intend that you should see the entire field stop at all times...

... It does make me wonder what the Minolta was designed to do, since viewing it without glasses only gives you, at most about 8.8°. The design leaves more than 2° hidden from the viewer, unless whats out of view is unusable anyways...

Is it just marketing and bragging rights from another era? 11°! Widefield!

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Well, that was exactly my impression when I first tried a superwidefield 11º binocular. The eyepieces were humungous, and you could lean sideways to try and reach the field stop on one side, and then rotate to try and do the same the other way, like if you were trying to see the sides of a room by looking through the keyhole, so to speak. Hence my question: why design a 11º binocular when you will never be able to use more than... 8 or 9º?

Another interesting point you make "if your pupil is at the maximum aperture (5mm for a 7x35) then maybe the field stop is visible at the correct eye relief, but at 3mm in bright daylight, it may not be. That would also have the convenient benefit of hiding the less corrected edge of the field from the viewer most of the time".
If I get this right... does this mean that at night (with expanded pupils) I should be able to enjoy a wider FOV? I never thought about this. Or did I just misunderstood you and made this up o

Omid said:

... making FOV extra large doesn't really help. An apparent FOV of about 60 to 65 degree is enough. More than that creates sever ergonomic problems

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Well, that's probably what I was thinking, but I didn't find the right way to put it into words, like you just did The lesson I learned with the "humble" Monarch 7 8x30 (at 65º) is a good one. I find they give more than enough. "More is better" seems to be a reasonable mantra for FOV, but, as you point out, more than plenty might easily bring more problems than benefits (well, except in few cases like say the Nikon WX ). I just ordered a 60º Swarovski 8x30 CL. I was a bit wary of the performance the 60º FOV might provide, but now I think I'll welcome it with other eyes.

I am following a different approach to increasing the FOV of binoculars: making their stereoscopic field of view larger than their monoscopic (is that a word?) field of view. See the thread called New Horizons II

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I don't recall having read that. There I go!! Thanks!

Omid said:

In agreement with your observations, it has also been my experience that once you get past tunnel-vision level, making FOV extra large doesn't really help. An apparent FOV of about 60 to 65 degree is enough. More than that creates sever ergonomic problems: large FOV must be accompanied with longer eye relief to allow for the center of rotation of your eye to be positioned at the exit pupil.

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Not necessarily, at least not IME. The old Zeiss 10x50 with its Erfle eyepieces and its ~74 degree AFOV (130m at 1000m) works pretty well for me. Not sharp at the edges, of course, but good enough to notice flying birds and so on. And of course the Erfles are not at all suitable for spectacle wearers.

BTW, I think some old studies showed that any increase in the field of view up to about 90 degrees "works" for most users. Above that most users begin to feel uncomfortable because they can't use the edge of the field of view as a reference point anymore.

That said, I personally feel the quest for wider and wider fields of view isn't necessarily always a good thing. There ain't nothing like a free lunch, and (very) wide fields of view aren't without their own problems. For instance, smaller fields of view mean simpler eyepieces, hence less weight and higher transmission, and of course fewer things that can go wrong during the manufacturing process.

Like you said, an AFOV of ~60-65 degrees works nicely.

Hermann

It depends if a person's eyes are on stalks or recessed or somewhere in between.
Also the size of a person's nose and face.

With the Minolta Standard MK 7x 35, 8x40 and 10x50 I can see most of the field if my eyes are absolutely straight up/down.
All these binoculars have the same back end.
The eyecups must be folded right down or even cut off.
If I tilt my head I cannot see the whole field, although I can see the whole field easily in the Leica 8x32BA even at a tilted angle.

So the amount of field seen is person dependent.
I like Nagler 82 degree eyepieces but not Ethos 100 degree eyepieces.

I have no problem seeing most of the field with 10x50 EWA Porroprism binoculars with from 7.5 to 7.9 degree fields.
I have quite a few from different makers.
It is true I use them mainly at night but the Minolta binoculars were also used in the daytime.
The Minolta 10x50 with 7.8 degree field, 7.65 degree easily seen, was my main binocular for ten years. I never had a problem with it, until it went out of alignment with heavy use. I wish it was fully multicoated.

B.

yarrellii said:

Any comments or ideas are more than welcome.

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Your question is just one end of the stick. The other end should read: What’s the use of an extra-wide field binocular WHEN the outer 1/3 to 1/2 of the field is garbage?

It seems that the people who are the most critical of optical products that don’t provide the contrast and resolution of those made for NASA or the Defense Department are also the ones who covet the ultra-wide (read: unrealistic) field of view. “Hey, y’all, I done got me a super, extreme, ultra-wide binocular. The outer 1/2 of the field performs like crap, but I still have what really counts ... my braggin’ rights.”

I was once thrown off BF because the powers that be—and a couple of thin skinners—were offended because I didn’t follow their deceptive rules of political correctness. So, I had better rush on to point out that ONLY ONCE in 14 years did I ever say anything in anger. I love my brothers and sisters who appreciate binocular viewing. I just don’t think it wrong to raise the voice of reason from time to time.

A Story:

A group of men decided to climb to the top of a high hill to enjoy a sunset. Because of a certain meteorological phenomena, it was supposed to be fantastic, a once in a lifetime view. They were not disappointed; it was everything they were told and they chose to remain a while after the event.
Darkness came quickly. Someone said, “I’m getting cold. Did anyone bring a jacket? No one did. In addition, no one brought a flashlight—torch for my Brit friends. Why should they? Everything was well-lighted when they were going UP the hill.

After a few trips over rocks and roots, and a few times of wondering off the trail into various uncomfortable thickets, they all got down safely. They were cold, tired, and frustrated ... but safe.

How much more pleasant would the experience have been if they had taken a little time to think things through before starting out?

So, it is with binoculars. There are laws of physics and finance that govern what can and can’t be done in designing instruments for a given market. Life could be so much better for observers if they understood those laws and the quirks and limitations of their own physiology, which plays a tremendous part in the picture—although usually ignored—and is why there are so few things that can be said about binoculars that remain the same from observer to observer. :cat:

Bless all.

Bill

yarrellii said:

Another interesting point you make "if your pupil is at the maximum aperture (5mm for a 7x35) then maybe the field stop is visible at the correct eye relief, but at 3mm in bright daylight, it may not be. That would also have the convenient benefit of hiding the less corrected edge of the field from the viewer most of the time".
If I get this right... does this mean that at night (with expanded pupils) I should be able to enjoy a wider FOV? I never thought about this. Or did I just misunderstood you and made this up o

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Its a conjecture, based on your observation that you cannot see the entire field in daylight, which suggests that the AFOV is wider than your pupil's ability to perceive the entire field. If your pupil is larger, you should see more of the field. Try the Minolta in the dark, and see what results you get.

-Bill

WJC said:

Your question is just one end of the stick. The other end should read: What’s the use of an extra-wide field binocular WHEN the outer 1/3 to 1/2 of the field is garbage?

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I love your sense of understatement! ;-)

The extra field is well worth it, even if poorer quality, when one catches a fireball that would have been missed.
Or perhaps a bear in the daytime.

I don't care a damn about bragging rights.
I care about observing.
Most of my observing is carried out alone. there is no one to brag to.

On one of my few observing trips with a group of astronomers I took the Celestron 20x80.
The Celestron 20x80 has a 3.5 degree field.
Everyone on La Palma said Comet Halley was best seen in this wide field binocular and not other binoculars or telescopes.

The Zeiss 20x60S has a very curved field. For me the edge in this binocular is just fuzzy.
However, I prefer that the field is there.
This is the finest hand held binocular that I have used.

B.

Binastro said:

The extra field is well worth it, even if poorer quality, when one catches a fireball that would have been missed.
Or perhaps a bear in the daytime.

B.

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That makes sense, but if it is not designed to be seen with your naked eye, then what was the manufacturer's intent? Or is the inability to see the entire field just user 'error'?

-b.

Some time back there was a somewhat similar discussion which led me to look at the exit pupil and eye relief on just a couple of binoculars that differ significantly in how readily the edge of the field of view could be viewed directly. No problem with the 64° afov but the 58° was a bit of a pain. The first point is that on both the effective ER was apparently shorter when the the binoculars were stopped down as they would be in bright light. The 58° binocular shortened more than the 64°. The second revelation was that the 58° binocular exit pupil appeared to be flat, wheras the ER on the 64° binocular varied with angle of view, suggesting a curved EP. I'm not sure I really understand how these two observations explain the practical ease of use difference on these two binoculars. let alone the very wide view options under discussion. It just seems there is another tier of optical complexity we have yet to understand.

David

Hi,

the maximum apparent field of view I can see without moving my eyes is roughly 80 degrees. Since moving the eyes is not very comfortable, with hand-held binoculars adjusting the aim is much preferable. This might be different with a large telescope and there is a lot of astro eyepieces out there with 100 or even 120 degrees of afov.

So I would say - up to 80 degrees afov is usable - even if it's a bit blurry (due to field curvature or real off-axis aberrations)... you will still notice the movement of a bird taking off and can quickly adjust the view to get it into the sweet spot.

Joachim

I currently keep a MIJ Leupold 8x42 in my car. The 6.2° FOV is quite sharp to the edges. In a way, the well-defined edges enhance the pleasure of viewing what's inside.

This morning I tried the Nikon EII 8x30.
It was bright sunshine so my pupils would be small.

Both field stops are easy to see. They are sharp.
The binocular gives a beautiful view and is very bright. Too bright this morning. I would have liked neutral density filters.
Eye placement is very easy for me with the EII unlike the Nikon 8x32 SE.
The eyecups were fully up on the EII.

But I could see well past the field stops, and if the EII provided 9.3 degrees I would see all of that.
The measured EII field on star separations is 8.85 degrees.

I can see 10.5 degrees of field on the Minolta 7x35 Standard MK fairly easily if I am looking horizontally straight ahead.
If I am looking high into the sky the field is reduced as I cannot get my eyes close enough.
I can see the measured 11.05 degree full field if I press my eyes very close to the eyepiece.
This is not comfortable.

B.

Well my conjectures are out the window!
Thanks for sharing your results Binastro.
It seems the user is the biggest variable, as several have suggested.

-Bill