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Old Saturday 21st October 2017, 16:56   #1
2weels
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Why do you need a wide field of view for birding?

I am seeing from discussions on the internet that birding calls for a wide field of view. It's not obvious to me why. Is it because birds move around and you will lose them if you don't have a wide FOV?

It seems you would try to fill the view with the bird, in which case FOV won't help when the bird moves away to a new position.

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Old Saturday 21st October 2017, 17:13   #2
Egrets Ivadafew
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From one amateur to another, imagine trying to find an owl in a pitch Black Forest using a pencil thin torch beam, that's a narrow fov taken to extremes. Then imagine looking for one with a WW2 anti aircraft searchlight. Again it's an extreme but that's a wide fov. At a set magnification (say 8x), varying fovs will make no difference to the size of the magnified bird. More experienced members on this site can give a better explanation.
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Old Saturday 21st October 2017, 19:47   #3
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WW2 searchlights had narrow beams that were bright at 20,000ft, maybe further slant distance.
Maybe 5ft diameter leaving searchlights.
Several were used at different baselines to intercept each other at aircraft height.

For me birding binoculars generally have narrow fields. Say 7 degrees for 8x.
I want at least 9 degrees at 8x.
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Old Saturday 21st October 2017, 20:59   #4
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Quote:
Originally Posted by 2weels View Post
I am seeing from discussions on the internet that birding calls for a wide field of view. It's not obvious to me why. Is it because birds move around and you will lose them if you don't have a wide FOV?

It seems you would try to fill the view with the bird, in which case FOV won't help when the bird moves away to a new position.

Thanks
Jim
Yes, it's easier with a wider FOV, especially at closer distance with fast moving birds. Larger depth of field also makes things easier with 7x-8x compared to a 10x binocular.

But there's no right or wrong here, just different preferences.
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Old Sunday 22nd October 2017, 00:15   #5
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Don't forget that wide field binoculars often have short eye relief so try them out first to see if you can use them comfortably. Wide field binoculars can also have long eye relief but in most cases they will be more expensive than those with short eye relief.

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Old Sunday 22nd October 2017, 03:01   #6
2weels
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Quote:
Originally Posted by Egrets Ivadafew View Post
From one amateur to another, imagine trying to find an owl in a pitch Black Forest using a pencil thin torch beam, that's a narrow fov taken to extremes. Then imagine looking for one with a WW2 anti aircraft searchlight. Again it's an extreme but that's a wide fov. At a set magnification (say 8x), varying fovs will make no difference to the size of the magnified bird. More experienced members on this site can give a better explanation.
Good analogy, from somebody who is also a flashlight geek.
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Old Sunday 22nd October 2017, 05:04   #7
Chosun Juan
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2weels - it largely comes down to the natural range of human vision.

The central part (the cone of visual attention) having a range of about 55 (I've seen figures ranging from 40to 60), binocular vision combined of ~114, and a peripheral range of ~160. Read any of the Wiki articles on the human eye as a good place to start.

This is interesting https://petapixel.com/2012/11/17/the...the-human-eye/

You want the Fov of your binoculars to be well corrected and reasonably sharp most of the way to the edge. 70 AFov is regarded as where extra wide starts, and is about the current limit of well corrected, reasonably light full size binoculars with sufficient eye relief for glasses wearers. Some prefer even wider fields and are not too concerned by softening at the edges, though if you want to maintain the ER, then weight (an expense start to climb). Non-glasses wearers (and short eye-lashed folk! :) have a bit of an advantage here.

Consequently anything less than 60 AFov is usually going to seem constricting and tunnel-like. My preference is for a sharpish to the edge AFov of ~70 but then again I wear glasses and like a lighter full size bin.

In an 8x bin this would be 154m @1km, so at a close distance of say 10m the field you can see is only 1.54m (5ft) ..... it doesn't take much for a little geewhizzit to suddenly flit 3 feet away and out of the field of view so that is why people prefer as much Fov as they can reasonably get. It also comes in handy for watching a couple of circling raptors at close range without losing one or more off the edge.

Have a look at the Nikon MHG in 8x .... one of the best wide Fov compromises on today's market.


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Last edited by Chosun Juan : Monday 23rd October 2017 at 00:57. Reason: accurate expression
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Old Sunday 22nd October 2017, 09:03   #8
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Hi,

actually a very wide FOV is still useful without being sharp to the edge - movement can still be seen even if slightly blurry and a hand-held pair is easily centered on the moving object.

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Old Sunday 22nd October 2017, 14:46   #9
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Chosun. Are you using the Nikon Monarch HG 8x42 now? Do you go birding at the Wialdra Creek near your home?
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Old Sunday 22nd October 2017, 15:09   #10
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Originally Posted by denco@comcast.n View Post
Chosun. Are you using the Nikon Monarch HG 8x42 now? Do you go birding at the Wialdra Creek near your home?
No, I've been flat biscuit - haven't been for a while ....



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Old Sunday 22nd October 2017, 19:37   #11
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It's simple - use bins with a good FOV for a while and then swap for a pair with a restricted FOV - you'll soon appreciate what you're missing!
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Old Sunday 22nd October 2017, 20:29   #12
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Quote:
Originally Posted by Chosun Juan View Post
2weels - it largely comes down to the natural range of human vision.

The central part (the fovea) having a range of about 55 (I've seen figures ranging from 40to 60), binocular vision combined of ~114, and a peripheral range of ~160. Read any of the Wiki articles on the human eye as a good place to start.

This is interesting https://petapixel.com/2012/11/17/the...the-human-eye/

You want the Fov of your binoculars to be well corrected and reasonably sharp most of the way to the edge. 70 AFov is regarded as where extra wide starts, and is about the current limit of well corrected, reasonably light full size binoculars with sufficient eye relief for glasses wearers. Some prefer even wider fields and are not too concerned by softening at the edges, though if you want to maintain the ER, then weight (an expense start to climb). Non-glasses wearers (and short eye-lashed folk! :) have a bit of an advantage here.

Consequently anything less than 60 AFov is usually going to seem constricting and tunnel-like. My preference is for a sharpish to the edge AFov of ~70 but then again I wear glasses and like a lighter full size bin.

In an 8x bin this would be 154m @1km, so at a close distance of say 10m the field you can see is only 1.54m (5ft) ..... it doesn't take much for a little geewhizzit to suddenly flit 3 feet away and out of the field of view so that is why people prefer as much Fov as they can reasonably get. It also comes in handy for watching a couple of circling raptors at close range without losing one or more off the edge.

Have a look at the Nikon MHG in 8x .... one of the best wide Fov compromises on today's market.


Chosun
Chosun,

Thats an interesting article and maybe worth reading. However, you might want to change "fovea" to "cone of visual attention" in the highlighted sentence.

After thinking about it the article is really pretty confusing, and I'm not sure it portrays the research findings very well. For one thing it confuses the eye's FOV with the region within which visual search typically occurs. There are no references at the end of the article making it impossible to clarify what he's saying.

PS. I wonder if the magic 70 deg. AFOV we all tend to agree about has anything to do with maximum eye movement for a typical human head? Maybe just a coincidence.

Ed
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Old Sunday 22nd October 2017, 22:03   #13
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What Chosun and Elkcub said is beyond my paygrade. I will put it in layman's terms why a big FOV is helpful for those of us on Bird Forum that don't have Phd's like me. Take a couple of toilet paper rolls and put them up to your eyes and now look around and try to find something. Now remove them and try it again. Which did you prefer?
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Old Monday 23rd October 2017, 01:44   #14
Chosun Juan
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Originally Posted by elkcub View Post
...... PS. I wonder if the magic 70 deg. AFOV we all tend to agree about has anything to do with maximum eye movement for a typical human head? Maybe just a coincidence.

Ed
Thanks Ed, previous post Edited to "the cone of visual attention" which is of course what I was meaning to say Strictly speaking the Fovea's Fov is much much narrower, and the 'normal' (whatever that is!) day to day vision comprises that and all sorts of near to mid peripheral vision which fall in that zone of roughly straight ahead, and is what we concentrate on, focus on, or 'notice' - within the well known limitations of gorillas in the room! :)

It neatly corresponds to the maximum eye movement graphic you presented, and so I would think is an evolutionary solution for us humans (as an aside I think it is interesting to wonder where that evolution will take us when we have preschoolers with heads buried right up close to digital display devices flashing away in rapidly changing part second scene shots?! There seems to be a rising incidence of myopia amongst young school children and a corresponding? decrease in attention spans! :)

As far as the 70 AFov goes, yes I agree - I think as a glasses wearer there are 3 things at play:-
1. For us, that's about where current bin offerings have taken us to - I'm not aware of any recent offerings that exceed 70 AFov and give long enough eye relief for glasses wearers ....
2. The range of maximum eye movement as you presented
3. The neatly overlapping peripheral vision range as below:
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https://en.m.wikipedia.org/wiki/Peripheral_vision

I really do find 60 AFov bins somehow 'confining', whereas 70 is nice - I would like to see a bit more for glasses wearers - I think we find a bit of peripheral view comforting and natural - and when you crunch the numbers it's amazing to think just how little a geewhizzit has to flit to pop out of the Fov at close range - even with a 70 AFov .


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Old Monday 23rd October 2017, 09:31   #15
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field of view! I don't know about the rest of you on here but I find it quite easy t
o move from left to right when viewing at distance. in close up i.m only interested in depth of view!
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Old Monday 23rd October 2017, 19:00   #16
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field of view! I don't know about the rest of you on here but I find it quite easy t
o move from left to right when viewing at distance. in close up i.m only interested in depth of view!
But if you have a wider FOV you can pick up more birds in the edge of the FOV and then you know whether to move left or right to center the bird.
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Old Saturday 28th October 2017, 14:42   #17
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Filling the field of view means using high powers, which will be jiggly to try to hand hold and suffer worse from seeing conditions. Finding birds at high power requires good memory of the scene to know where you need to point. Wide field allows you to point easy, avoids jiggle and enables you to catch motion at the edge of your field of view to help spot things you didn’t realise were there.
As mentioned, it doesn’t have to be sharp to the edge as your eyes aren’t, you scan with your head and bins, not your eyes and you’ll not notice the slightly softer field edge.
I got a nice pair of >75degree bins and won’t be returning to tunnel vision anytime soon.

PEterW
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Old Saturday 28th October 2017, 15:07   #18
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At the risk of stating the obvious, I will note that wllmspd is referring to Apparent Field of View, the field of the eyepiece rather than the field of the overall instrument.
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Old Saturday 28th October 2017, 15:53   #19
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Is the Nikon Action/Aculon 7x35 the only current model of binocular for nature/bird watching with an AFOV that wide? Thanks.
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Old Saturday 28th October 2017, 19:09   #20
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Yes, there are two fields of view. Even my 2x54 homebrew bons inly guve 20something degrees real field of view.
My instrument of choice is a rangemaster 7x, 77degree Afov and about 11degree “real”Fov. My preference is for wide AFOV with whatever instrument I am using. There are plenty of cheap old Porro 7x35 out there, not lightweight and with small eye relief, but nice wide views.

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Old Wednesday 1st November 2017, 10:22   #21
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It's somewhat similar to trying to hit a bird with a shotgun (wide field binoculars) versus a rifle. The greater "spread" that a wide field of view gives you helps in initial target acquisition and helps you stay with fast flying birds. This isn't an issue if you know exactly where the birds are ie. on a bird feeder or similar but would be for something like a prairie falcon zooming over your badlands at 60 mph (and many other birding situations). The extra wide field 7x35s are probably not absolutely necessary, although very nice to have, especially if you don't use binoculars with glasses/spectacles. I'd require at least the industry standard though, which seems to be about 110m at 1000m for 10x, 130m at 1000m for 8x and 140m (I think) at 1000m for 7x.

Regarding filling the view with the bird - it's very seldom possible to do that with binoculars unless you're observing city birds and/or very large birds. Even with a spotting scope it's not easy sometimes.
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