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AFOV and Eye Comfort

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#1 tylersk90

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Posted 15 January 2021 - 11:55 AM

Hello everyone!

 

Maybe what I'm searching for doesn't exist, or maybe my problems are self-inflicted (a physiological problem) .  Either way, I'd love to hear what the forum has to say.

 

When I look through binoculars with a wide AFOV (70deg) -or any AFOV for that matter- (the larger AFOV just seems to exacerbate the issue) I "know" the clean field stops are there around the full circle of view, but I can only see it all clearly if I take special care to focus my eyesight dead-center, do not direct my gaze off-axis and take it all in with my "periphery".  I find it rather annoying to glance at something in the leftmost 25% of the AFOV, only to find it is blacked out when I look at it.  The field stops are clean when not staring at them, but if I inspect them directly (non-peripherally) they dissolve, blur, and darken.  

 

I understand binoculars are made to be used staring dead-on at an object, but is there no binocular spec that allows one to examine the entire AFOV without my eyes playing tricks?

 

If it is inherent in the design, what would I look for in a pair to minimize this effect?  Smaller AFOV? Less magnification?  Larger exit pupil?

 

The main suspect is the NL Pure 10x42; great optically, but this super wide AFOV is becoming bittersweet, offering images in the AFOV that can't be examined unless I point the binocular more directly.  I don't know if returning them for an SLC 8x56 (more eye relief, larger exit pupil, smaller AFOV, lower mag) or the NL Pure 8x42 (lower mag, larger exit pupil)  would minimize this issue.  FWIW I tried out a Vortex Crossfire 8x42 at my local store, and while less bothersome, it was still hard to inspect images in the extremities of the AFOV.

 

To summarize:  Would a larger exit pupil, smaller AFOV or less magnification bring me closer to my goal of having my binocular display a circular image that I can let my eyes follow along the field stop edges without the view deteriorating?  For example, If I position my view with an in-focus fence post on the edge, is there any pair of binoculars on the market that allow me to inspect the fence post without moving my binocular to position the fence post front and center?  Maybe these super-wide AFOV are just meant to catch peripheral movement but not provide further detail until I reposition my binocular?  

 

My ideal AFOV would be more like a window: providing clear and defined field stops while I hold the binocular steady, that allows my eye to roam around the edges of the AFOV/field stop without parts of the display dissolving.  

 

Maybe what I ask for doesn't exist.. confused1.gif

 

Clear Skies and calm viewing,

 

Tyler



#2 garret

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Posted 15 January 2021 - 01:33 PM

I have several eyepieces for my binocular telescope, they have 76; 72; 65 and 62 degree AFOV

with the 76 degree Morpheus eyepieces I can not see the edge without some blurring of the view, with the 72 degree Delos blurring is almost gone and with the 65 degree Vixen eyepieces there isn't any blurring (moving only my eyes to the edge of the field)

There are many reports of users with 100 degree eyepieces in their binoculars or binoviewers without any report of problems of blurry edges...

Beyond  about 70 degree (35 degree in any direction)  our eyes move away from the cone of light and therefore we cannot see the edge without blurring/ vignetting/ distortion.


Edited by garret, 15 January 2021 - 01:58 PM.


#3 SMark

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Posted 15 January 2021 - 01:42 PM

I generally term this as what I would call "eye comfort" and it seems to have everything to do with the eyepiece, or perhaps even the eye lens, design. It seems to me that flat eye lenses seem to be less fussy about eye position, while curved eye lenses are more fussy about eye position. I am one who much prefers wide angle views and have never had issues with turning my head toward what I want to look at. It just seems natural and what I would do when not using binoculars. But some binocular users seem to prefer to use binocular eyepieces like you might use a telescope eyepiece, and keep the binocular in a fixed position while using the eyeballs to move around the field of view. I guess this is what leads to extreme opinions regarding outer field aberrations. Some, like me, would prefer the wider AFOV, even with significant outer field aberrations. Others would much rather have a 40° AFOV that is perfectly flat and sharp, edge-to-edge. A 40° AFOV just doesn't excite me at all. But we all have wide ranging opinions on the matter. 

 

One case in point is the popularity of the discontinued Nikon SE series. Widely acclaimed to be one of the finest series of porros ever made, but also widely criticized for their potential to kidney bean or black out. I guess the eye relief figures into the equation, but I make most of these kind of judgments using wide angle 7x35's, and eye relief is always short with these, yet the eye comfort still varies significantly between binoculars. Nevertheless I did buy myself a 10x42 SE and could not get used to it. And wearing my glasses to accommodate the eye relief didn't seem to make things any better. So some of us seem to have better tolerance for these sorts of things, I guess. 


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#4 Rich V.

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Posted 15 January 2021 - 01:53 PM

I agree that a 65- 70° AFOV is the sweet spot in binos for me.  I tolerated a short eye relief 65° 16x binocular for many years but have now switched to a modern design long eye relief model with a similar AFOV which still retains a nice, flat field.  Viewing comfort is much better when viewing off axis with the better ER.  I don't have to squish my eyeballs into the eyepieces to get the best views anymore.

 

The common problem with super wide AFOVs is that ER is frequently compromised to achieve it in a compact form factor.  IMO, it's better to compromise AFOV a bit for the sake of viewing comfort.

 

I do enjoy 100° eyepieces in mono mode in my telescopes but it would be a waste in a bino for me.

 

Rich


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#5 gwlee

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Posted 15 January 2021 - 01:57 PM

Although it’s a cliche, binoculars are somewhat like shoes. You must experiment to find out what combination of optical features is most satisfying to you. I can’t see what you are describing, so can’t offer anything more helpful. 



#6 tmichaelbanks

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Posted 15 January 2021 - 02:29 PM

Hello tylersk90,

 

For those binoculars I have where I can see the hard field stop (Kowa 6.5x32, Nikon HG 10x42, Nikon M5 8x56, Pentax 20x60, and Oberwerk Ultra 15x70), I notice the same effect, i.e., look straight ahead and observe the hard stop easily, roll right or left with my eyes and can't see it any more.  I strongly suspect Mr. garret in Post #2 above is correct, that when you move your eyes they are positioned so that they are partly outside the exit pupil.

 

It is a very noticeable and consistent effect for me.  I wear eyeglasses with strong prescriptions so for the binos I list I can barely see the field stops except for the 20x60 where they are easily seen.



#7 tylersk90

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Posted 15 January 2021 - 04:20 PM

Thank you all for the input thus far.  So would perhaps a 60deg AFOV with 23mm eye relief (SLC 8x56) allow my eyes to roll around the visual frame more freely with less blackouts, etc. than my 70deg AFOV 18mm eye relief NL pure 10x42?

 

Just when you think you've fine-tuned the perfect parameters, another variable rears it's ugly head! lol.gif



#8 gwlee

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Posted 15 January 2021 - 05:00 PM

Thank you all for the input thus far.  So would perhaps a 60deg AFOV with 23mm eye relief (SLC 8x56) allow my eyes to roll around the visual frame more freely with less blackouts, etc. than my 70deg AFOV 18mm eye relief NL pure 10x42?

 

Just when you think you've fine-tuned the perfect parameters, another variable rears it's ugly head! lol.gif

FWIW, I find my 7x50 binocular with 50* AFOV, 7.5* TFOV, 7.1mm exit pupil, and 23mm of eye relief my most comfortable binocular to look through by a wide margin, but it has weaknesses in other areas. Letting my eyes roam around its 7.5 field of the stationary binocular is very comfortable and natural experience. This binocular is usually my first choice for lengthy observing sessions. 

 

My least comfortable binocular to look through is an 8x32 binocular with 65* AFOV, 8* TFOV, 4mm exit pupil, and 20mm of eye relief, but it has strengths in other areas. Both binoculars are high quality instruments. Without trying both, there’s no way for you to know which binocular you would find most comfortable to look through. 
 

I suspect that I would find the SLC 8x56 more comfortable to look through because its published specs are closer to my 7x50, but I wouldn’t know without trying both. Buying binoculars based on published specifications is as risky as buying shoes based on the size written on the box, but it’s a good place to start your search for the perfect binocular. 


Edited by gwlee, 15 January 2021 - 08:31 PM.


#9 PEterW

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Posted 15 January 2021 - 05:05 PM

You need eyeballs that pivot around the pupils so that they stay centred on the binocular exit pupils and so don’t black out when you want to look at the side edges of the field. You can move your head slightly side to side behind the binoculars to help. I like the extra wide AFOV for “space” and awareness even if I cannot always focus both eyes to the far edges of it.

PEter

#10 Jon Isaacs

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Posted 15 January 2021 - 05:16 PM

As has been said, eye comfort is a personal issue.

 

For me, it's primarily two things, enough eye relief and eye cups that don't get in the way. I recently have started just removing modern twist up eyecups and replacing them with rubber eyecups.  This has transformed more than one pair of binoculars.

 

There is some connection with AFoV since eye relief is a function of eye lends diameter and AFoV. For a given amount of eye relief, a wider AFoV requires a larger eye lens which makes the eyecups larger in diameter.

 

Modern eyecups tend to be overly bulky and get in way of easy positioning.. Removing them can work wonders..

 

Jon


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#11 DeanD

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Posted 15 January 2021 - 07:10 PM

As has been said, eye comfort is a personal issue.

 

For me, it's primarily two things, enough eye relief and eye cups that don't get in the way. I recently have started just removing modern twist up eyecups and replacing them with rubber eyecups.  This has transformed more than one pair of binoculars.

 

There is some connection with AFoV since eye relief is a function of eye lends diameter and AFoV. For a given amount of eye relief, a wider AFoV requires a larger eye lens which makes the eyecups larger in diameter.

 

Modern eyecups tend to be overly bulky and get in way of easy positioning.. Removing them can work wonders..

 

Jon

Hi Tyler,

 

Televue used to provide a "pupil guide" insert for the eyecups for their Radian and some Nagler eyepieces (not sure if they still do). See: https://www.televue....nstructions.pdf

 

This was just a do-nut piece of plastic that ensured your eye was properly centred. I have found it great for public viewing nights for people who aren't used to eye positioning. 

Perhaps something like this might help?

 

It would be a real shame to have to get rid of that NL Pure binocular! (I would happily assist by taking it off your hands! ;) )

 

Good luck,

 

Dean



#12 jimhoward999

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Posted 15 January 2021 - 07:18 PM

Yes a bigger exit pupil and/or a smaller AFOV should mitigate the issue.  If you want to move your eyes but not your head then you would need the exit pupil to be big enough to accommodate your pupil wander  


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#13 tylersk90

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Posted 15 January 2021 - 08:52 PM

Thank you all! Cloudy Nights is such a great forum! Very active and knowledgable.

 

Hearing these accounts plus the more I read (lots of good info regarding this on CN outside the Bino forum) I’m learning that I may be over reacting way too much. I can’t seem to stay content, I keep trying to nitpick every last detail, even if some of those are non-existant. I will keep all this info in mind, and I’m seeing why all the veterans of the forum own multiple pair! grin.gif

 

The 10x42’s are as close to perfect as I could hope for, I’m beginning to confirm what I originally suspected that no single binocular will benefit me greater, it’s not a matter of replacement, but one of addition lol.gif

 

Also, after extending the eyecups further I’m finding a more “settled” view. I think I’m just still getting used to the big screen hd 70deg lol


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#14 DeanD

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Posted 15 January 2021 - 09:07 PM

I think you are right. I just tried with some of my binos, and the same problem (I had never noticed it before: I have always moved my head and the binos a bit instead of just my eyes). I think, as per jimhoward999 it is simply do to your pupil moving away from the centre of the exit pupil, and the view being cut off/vignetted. This is exacerbated by the broad "cone" of light coming into a wide fov eyepiece. Good old 7x50 binos with a 7mm exit pupil and a narrower afov with a narrower cone of light would have had much less of a problem for this reason.

 

So, no reason to let go of your NL's and send them to me after all... frown.gif ;)

 

Happy viewing,

 

Dean


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#15 tylersk90

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Posted 15 January 2021 - 09:35 PM

“Cone” of light. Now that makes sense to me! Thank you. 
 

So in this case you would say a narrower slice of pizza is a good thing! tongue2.gif

 

 

 

My backyard skies are real dark tonight, (naked eye Andromeda!) and it has occurred to me the complaints from my OP at night are significantly less prominent in the dark. My earlier tests where staring out of a window with the sun directly overhead. 
 

I wasn't considering the size of my pupils!


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#16 DeanD

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Posted 15 January 2021 - 11:17 PM

 

So in this case you would say a narrower slice of pizza is a good thing! tongue2.gif

 

 

... only if it is from a bigger pizza!  yay.gif



#17 Neil Sanford

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Posted 16 January 2021 - 03:02 AM

When viewing I experience that extremely small axial (roll, pitch, yaw) movements of the binocular have quite obvious effects.  When IPD and focus of both tubes are all correct for my eyes, and I view a centered target, these little movements obviously change focus of the centered target.  I suspect what is happening has to do with precise alignment of both optical axes to both pupils. 

 

So I never just slap a bino up to my face and leave it at that.  I always try those little micro movements. 

 

Also -- this is probably quite personal -- I like to raise the bino to my eyes with just one hand.  I have the feeling that with two hands I am unconsciously aligning the bino to my body, but with one hand I get better initial alignment to my pupils. 



#18 MartinPond

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Posted 16 January 2021 - 10:43 AM

------------------------------

To summarize:  Would a larger exit pupil, smaller AFOV or less magnification bring me closer to my goal of having my binocular display a circular image that I can let my eyes follow along the field stop edges without the view deteriorating?  For example, If I position my view with an in-focus fence post on the edge, is there any pair of binoculars on the market that allow me to inspect the fence post without moving my binocular to position the fence post front and center?  Maybe these super-wide AFOV are just meant to catch peripheral movement but not provide further detail until I reposition my binocular?

---------------------------------------------------------

 

 

All of that....100% correct, for most wide binocs.

Most 70--85 D afov binoc eyepieces are only 60--75% sharp.

 

The problem is, you are wanting sharpness all the way across.

Now....on a very bright daylight trip, it gets better (pupils close down),

  but usually not at night.

 

Fancier eyepieces help a lot to get 55--63 afov sharp,

but more than that, all sharp, means spending a lot.



#19 sevenofnine

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Posted 17 January 2021 - 12:49 AM

Have you looked through the "Swarovision" types with the field flatteners? Seems like I remember that was what that model was all about. In a static view the edges and the center are nice and sharp. However, some birders didn't like them because when you pan you get a rolling effect. Others describe it as a rippling effect that takes some getting used to but the views are very impressive. And they should be at that price watching.gif



#20 Michael Rapp

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Posted 17 January 2021 - 01:56 PM

For the longest time, I equated comfort with AFOV.  (I don't wear glasses so eye relief, unless it was just ridiculously short, didn't really factor in for me.)  However, recently, I've noticed something.  Moving some of my eyepieces between scopes, an eyepiece that was inherently comfortable on one scope would be less comfortable on other.

 

Obviously, the AFOV didn't change.  It was then that I realized that perhaps most of my feeling of comfort was related to the exit pupil rather than the AFOV.  

 

Now how much this translates over to traditional binoculars with fixed eyepieces, I am not sure as most of them are exit pupils greater than four mm or so.



#21 gwlee

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Posted 17 January 2021 - 03:15 PM

For the longest time, I equated comfort with AFOV.  (I don't wear glasses so eye relief, unless it was just ridiculously short, didn't really factor in for me.)  However, recently, I've noticed something.  Moving some of my eyepieces between scopes, an eyepiece that was inherently comfortable on one scope would be less comfortable on other.

 

Obviously, the AFOV didn't change.  It was then that I realized that perhaps most of my feeling of comfort was related to the exit pupil rather than the AFOV.  

 

Now how much this translates over to traditional binoculars with fixed eyepieces, I am not sure as most of them are exit pupils greater than four mm or so.

I have done a lot of experimenting with refractors and binoculars to see how my viewing comfort is effected by the size of the exit pupil and found that, for me, comfort increases as exit pupil increases between 0.5mm to 7.1mm.

 

Consequently, for a hiking binocular that I carry long distances in steep terrain and use briefly, the 4mm exit pupil of my 8x32 is acceptable, but for all other purposes, I want at least a 5mm exit pupil in my binoculars. So that means ~50mm for 10x and ~42mm for 8x. 


Edited by gwlee, 17 January 2021 - 03:18 PM.

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