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What determines Field of View? (1 Viewer)

tpcollins

Well-known member
I thought maybe a particular ocular/objective combination contributed to the FoV but that doesn't seem to be the case unless I'm missing something. I sit about halfway up near the goal line at Michigan Stadium and when watching the other end of the field, when the QB drops back to pass I have to pull the binocs down to see where the pass goes.

My new Zeiss Victory 8x42 has about the same FoV as my old 8x32 ELs. The largest FoV I can find is the Zen Ray EDII 7x36 with a 477" FoV and a reasonable 16.8mm eye relief. Is there something with more FoV as reasonable as the Zen Ray? Thanks.
 
Hello TP,

The short answer is the field stop in the eyepieces. The field stop is roughly the narrowest diameter of eyepiece, the widest piece of unobstructed glass. If you compare a narrow field binocular with a wide field binocular, other things being equal, the latter has the wider field stop.
To get a wide field with a sharp image across the greater part of the field requires a sophisticated design of the eyepiece.

I am sure that others will add to my rudimentary explanation.

Happy bird watching,
Arthur Pinewood :hi:
 
Don't believe the published FOV specs too literally - give them a try in the flesh, if possible. The distance of your eyes from the eyepeice will also be factor, as those of us with glasses know. FOV is larger when I look without my glasses so that my eyes are close to the eyepeice, but of course that isn't possible in the field.
 
Is the length of the barrel a critical factor? I´m a technophobe, and daydreamed through maths classes over thirty years ago, but I imagine a shorter barrel will give a wider FOV (I´m seeing vague images of light cones entering the objectives, crossing and reversing at the oculars....)?
 
As Pinewood says it's the acceptance angle of the eyepiece (i.e. the AFOV) and the magnification that set the FOV.

AFOV = 2 * arctan ( M * FOV /2 )

Then the question changes to why do eyepieces have a given AFOV. That's all part of the trade off of field curvature and astigmatism at the edge of field with other parameters like eye relief, complexity/cost and so on.

We've also had a recent thread on why compact bins have wider FOVs than larger bins. That comes into the argument between bin sizes.

The ZR 7x36 is the widest production 7x bin out there right now (though I can't see the whole field with my glasses on).
 
Hello TP,

The short answer is the field stop in the eyepieces. The field stop is roughly the narrowest diameter of eyepiece, the widest piece of unobstructed glass. If you compare a narrow field binocular with a wide field binocular, other things being equal, the latter has the wider field stop.
To get a wide field with a sharp image across the greater part of the field requires a sophisticated design of the eyepiece.

I am sure that others will add to my rudimentary explanation.

Happy bird watching,
Arthur Pinewood :hi:

For most people, that says it all. I'll elaborate just a tad: "a sophisticated design of the eyepiece" = $$$.

I once removed the field stop from an Orthoscopic-design telescope eyepiece so that I could see a larger field of view. (The field stop was obviously accessible -- most are between the lenses.) Yes, I could see a larger field as a result, but that which was previously covered was not very sharp!

Howard
 

filters? o:)

We love this binocular! The sharp wide-angle views are just great - but it's the built-in filters that mark this binocular out as exceptional. OK, filters? You're thinking this sounds like something 'Q' would give James Bond: "Listen carefully 007: as well as the filters there's also a mini-flame-thrower - for goodness sake don't get the switches mixed up!"

Actually the built-in filters aren't just a gimmick, they really work. There are two colour filters, red and yellow, that can be switched into the light path (two for each eyepiece) and they can be used together to create orange. We found that in some lighting conditions, horizon haze, overcast, or just dim light, the filters could be very effective. In our own test we found the yellow for contrast enhancement the most useful filter. The yellow filter seemed to work in a wide variety of viewing situations, especially in twilight. The filters can be flicked in and out with your fingertips, and do not require the binocular to be taken away from the eyes.
 
As Pinewood says it's the acceptance angle of the eyepiece (i.e. the AFOV) and the magnification that set the FOV.

AFOV = 2 * arctan ( M * FOV /2 )

Then the question changes to why do eyepieces have a given AFOV. That's all part of the trade off of field curvature and astigmatism at the edge of field with other parameters like eye relief, complexity/cost and so on.

We've also had a recent thread on why compact bins have wider FOVs than larger bins. That comes into the argument between bin sizes.

The ZR 7x36 is the widest production 7x bin out there right now (though I can't see the whole field with my glasses on).

Actually the 7x35 Nikon Extreme ATB beats the Zen Ray for FOV at 1,000 yards.
 
Doh! Of course the Nikon's are 9.3° and the ZR are 9.1°.

I have a set in my collection. For some reason I was (mis)remembering them as 9.0 or less.

That said I prefer the edge performance (and the view) of the ZR to the Nikon though the overall ER is better in the Nikon. There is only a factor of four price difference between them. ;)
 
I have considered Nikon AE before. From what I read, it is not fully multi-coated and the close focus is too long to make an ideal birding bin. A Porro 7x32 or 7x35 Nikon SE with 9 degree FOV will be a perfect combination
 
I have considered Nikon AE before. From what I read, it is not fully multi-coated and the close focus is too long to make an ideal birding bin. A Porro 7x32 or 7x35 Nikon SE with 9 degree FOV will be a perfect combination

Falcon:

The SE that you would be referring to is the 8x32 SE and I would agree that it
would be the ideal birding bin. They have a 7.5 degree FOV but every bit of it
is as clear and perfect as you could want.

When you are talking 9 degree, in most cases, the outer 25% is distorted and
so is not as useful. ;)

Just to compare, the Nikon Actions, and the Action Extremes they are good binoculars, but now when you mention the Nikon SE you are now stepping up to the very best viewing you can find.

Jerry
 
Doh! Of course the Nikon's are 9.3° and the ZR are 9.1°.

I have a set in my collection. For some reason I was (mis)remembering them as 9.0 or less.

That said I prefer the edge performance (and the view) of the ZR to the Nikon though the overall ER is better in the Nikon. There is only a factor of four price difference between them. ;)

Those 7x35 Nikon bins offer a lot of performance for a moderate price. Certainly not perfect but they will get the job done and the binocular budget will have funds for other goodies.
 
Those 7x35 Nikon bins offer a lot of performance for a moderate price. Certainly not perfect but they will get the job done and the binocular budget will have funds for other goodies.

I agree. And so did the bin testers at Cornell. The Nikon 7x35 ATB was the standard starter bin with good ER, low on shakes and wide FOV for quite a while. It's downside is weight but I really like the grip that comes from the "canted" prisms.

The "9 degree 7x35 SE" comment is an interesting one. One of the things that makes the SE such a nice bin is it's flat field. I'm not sure if they can do that over such a wide field. Though from scaling the 8x and 10x you should be able to get a 450 feet @ 100 yards or 8.6° FOV. The same as the Zeiss 7x42 FL.

It will never happen though. ;)
 
I agree. And so did the bin testers at Cornell. The Nikon 7x35 ATB was the standard starter bin with good ER, low on shakes and wide FOV for quite a while. It's downside is weight but I really like the grip that comes from the "canted" prisms.

The "9 degree 7x35 SE" comment is an interesting one. One of the things that makes the SE such a nice bin is it's flat field. I'm not sure if they can do that over such a wide field. Though from scaling the 8x and 10x you should be able to get a 450 feet @ 100 yards or 8.6° FOV. The same as the Zeiss 7x42 FL.

It will never happen though. ;)


I enjoy wide field binoculars myself. 8x30 Nikon EII's with their 8.8 degree field of view are a lot of fun and they too have the canted prism housings. 8x32 Unitron 8x32's with an 8 degree field deliver good images and have a very compact traditional porro construction. They are re-badged Vixen Ultima bins that were also sold by Celestron.

I keep hoping we will see a modern ultra wide field bin with 11+ degrees. Most binoocular development seems to be directed toward the roof prism design with goodies like waterproofing, armoring and water repellent coatings. So I'll keep trolling Ebay for one of the older bins.:t:
 
8x32 Unitron 8x32's with an 8 degree field deliver good images and have a very compact traditional porro construction. They are re-badged Vixen Ultima bins that were also sold by Celestron.

The Celestron Ultima DX 8x32, perhaps with a 8.2° FOV. I have a pair. Sharp with some field curvature. Oversized prisms (the design looks like it was meant to have other objective sizes like the SE). Heavy at 1kg. A rather good bird feeder bin.

I keep hoping we will see a modern ultra wide field bin with 11+ degrees. Most binoocular development seems to be directed toward the roof prism design with goodies like waterproofing, armoring and water repellent coatings. So I'll keep trolling Ebay for one of the older bins.:t:

I think the problem is with stray light in roof or more particularly roof with internal focusing. I think there are some compromises made with baffling when the internal focuser is between the objective and the roof prism and that limits how big and acceptance angle you can have in the eyepiece without picking up . The older porros (especially the 1950s and 1960s "wide angle" 10x50 and similar) often put a fair amount of extra baffling in that section.

Just speculation but we've seen the problem ZR had when scaling the "Chinese ED" design to 7x and going for a wider field. The "glare fixes" in the second revision fixed the issue were mostly about reducing scattering in that part of the bin.
 
...
I keep hoping we will see a modern ultra wide field bin with 11+ degrees. Most binoocular development seems to be directed toward the roof prism design with goodies like waterproofing, armoring and water repellent coatings. So I'll keep trolling Ebay for one of the older bins.:t:

Keep an eye out for an 8x40 Linet Imperial with BaK4 prisms and a 12° FOV. They were made by Hiyoshi Kogaku in the early 1980s, with the same quality as the Swift Audubon (Type 2). A 96° apparent field is quite an experience, altho one can overdo a good thing.

Ed
 
Keep an eye out for an 8x40 Linet Imperial with BaK4 prisms and a 12° FOV. They were made by Hiyoshi Kogaku in the early 1980s, with the same quality as the Swift Audubon (Type 2). A 96° apparent field is quite an experience, altho one can overdo a good thing.

Ed

Intriguing design. I'm not familiar with the brand. Was it sold mostly in Japan?
 
I assume they were sold in the US and elsewhere, but not in large numbers. Fan Tau had one shown on his website (a 7x35, as I recall), but his site recently vanished!. (What a loss.) Last year I asked him his impressions of the Linet, but he could only go by memory since he had sold it years before.

Swift, of course, produced the Model 766 7x35 Holiday Mk II, with 600 ft. (11.5°) FOV during the same period. The apparent field is 11.5 x 7 = 80.5°, which is still quite wide. Unfortunately, mine was rather disappointing as it turned out to have BK7 prisms and considerable exit pupil vignetting. It is also plagued by poor baffling and excessive reflections off the eyelens. I suspect earlier 766 models may have been designed better.

Anyway, using the Linet and my Swift Holiday as guideposts, I'm not sure there is much advantage to apparent angles that exceed 70°, particularly since people tend to crab about the view not being clear to the very edge. I've been meaning to take the Linet into the field to see what, if any, thrills it produces.

Ed
 
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