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Field of view (1 Viewer)

JabaliHunter

Well-known member
Another beginner's question:

I often read comments regarding the narrow field of view of some binoculars, particularly as a criticism of for example 10x42 v 8/8.5x42.

Why is the difference so appreciable?

A popular 10x42 has the following specs:
FOV@1000m - 112m
FOV real - 6.4*
FOV apparent - 60*

A popular 8.5x42 has the following specs:
FOV@1000m - 133m
FOV real - 7.6*
FOV apparent - 60*

The difference in linear FOV is 21m. Given that a lot of emphasis is also placed on the close focus ability of binoculars, of you scale back the linear FOV to closer distances, the difference is just 2.1m at 100m, 1.05m at 50m, or 0.53m @ 25m.

On paper it would seem that the difference is insignificant (assuming the maths is correct ;) ). Or, doesn't it work like that and is there another factor at play here?
 
The numbers are correct.
The difference in field of view is about 20%, which does make a perceptible impact.
That said, people seem to get comfortable with whatever field their glass provides pretty quickly, so it is not a killer issue, at least imho. Certainly the range of fields available is narrow, maybe from 5.5* to 8.5*.
There are no 12* field of view binocs out there now afaik, although if memory serves there were some ultra wide angle Japanese porros sold in the 60s that had a 625ft FoV at 1000 yards, over 13*. Eye relief was under 10mm, unfortunately.
 
These are some of my thoughts about extra wide AFOV/FOV.

I use optics for three main purposes:
1. Measuring optics, such as range finders, test and surveying instruments, which will not be discussed here, but are considered detail optics.
2. Detail optics, these are for ID’s or study of details, reading.
3. Scanning optics, for sweeping larger areas, in general just locating movements.

For detail optics such as my pocket binoculars, which are just pulled out when I want to have a closer look at something, already located, and just need more detail. This consists of about 90% of my binocular usage.

Scanning optics is what I typically use on weekends and when just searching large areas for movement or signs of things that may be of interest. Searching for random birds, etc.

For detail binoculars I like small to moderate FOV/AFOV for various reasons, mostly image quality. For myself, I am content most of the time with AFOV’s on the order of 50-55° or so, but you have to keep in mind that 95% of my optics use is working with instruments around 30x50 and FOV’s around 1.5 degrees and exit pupils about 1.3 mm, so 6.5 degree FOV’s and 2.5 to 4 mm exit pupils seem very large in comparison. I also tend to center everything on axis since about all my optics use involves a crosshair reticule.


Most of the discussion on Bird Forum seems to be in favor of very large FOV’s and AFOV’s along with greater eye relief. But there is a lot of discontent with the edge performance of the larger AFOV/FOV’s. It has to be kept in mind that a large FOV has to be a compromise of optical performance or a great deal more expensive to make the necessary corrections (Swarovision, for example).

The following considerations need to be accounted for with wide angle FOV’s:

1. As you get farther off axis, natural vignetting increases exponentially as the angle increases (darker edges).
2. Field curvature increases with off axis magnitude.
3. Astigmatism increases with off axis magnitude.
4. Shorter eye relief for the same size eye lens.
5. Increased transverse CA.

In short, smaller AFOV’s equal sharper, brighter images (eyepieces below 55 degrees AFOV are a lot easier to build and quite a bit more economical) and large AFOV’s equal larger scanning area, but with greater image degradation past 45-50 degree AFOV plus a premium cost for the larger FOV if well corrected.

I like a large AFOV as well as the next fellow, but I am well aware of the fact that good edges with large eye relief is going to cost me $$$.
 
Ron, I agree that there are increasing problems (nee tradeoffs) with increased AFOVs. That said I am a died-in-the-wool wide FOV fan. Interestingly for me, some bins with uber wide FOVs are not very distracting despite edge flaws. Others are annoying as all get out. Obviously this varies among users. An example is the not long ago discontinued Carson SW-842 porro. It was an 8.5x42 with an 11* TFOV for a 578' view. Some on CloudyNights loved it.... I found it very distracting and sold mine. On the other hand my ZOMZ-Kronos 6x30 with a claimed 12.5* TFOV provides a very enjoyable wide view (there's a nice review of it by Holger Merlitz on line) as do my vintage Binolux 7x35 porros cited in my signature field. I had other vintage uber wide field 7x35s including some touted as "grails" but they were sold off as I personally was happiest with the Binolux I kept. I'm not sure I can identify what specific characteristics have made some uber wide field bins relaxing and not distracting to use and others not even close.....
 
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I should first say that I recognize that there are a vast diversity of different uses for binoculars, not all of which require a super-large field of view.

However... For birding, I have certainly found that a wide field of view is a huge benefit (and, I think, one often overlooked by many people), primarily for *finding* birds. I think Cameron Cox's remarks on the benefits of wide FOV's in the following post are spot on (he talks about this issue in the 3rd through 5th paragraphs):

http://www.birdforum.net/showpost.php?p=2179325&postcount=50
 
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What are you considering "ultra wide"?

The only pair of binoculars I have owned that I would consider "ultrawide" would be the 7x35 Nikon Action/Action EX. They had a 480+ field of view from what I remember. You might consider the Nikon E II 8x30 as Ultrawide for an 8x30 with its 460+ field of view. Other than that.....

I am aware of some inexpensive Bushnell models that advertise an ultrawide field of view (thinking the 5x30 model in particular). It does have it but the sweet spot was small and the edge distortion so excessive that I found it hard to use.

Some of the older model porro prism models were true "Ultrawide field" but I have next to no experience with those. Some others might.
 
What Are Some Of The Better Ultra Wide Fov Bins Ou There ?
I Would Like To Hear Comments, As I Am Looking For A Pair.
Thanks.

The best is the Nikon 8 x 30 EII. It has been discussed as much as any binocular on Bird Forum, just check through the Nikon forums. I believe they are still being sold in England so look around for them and grab one while you can. It is a classic.

Bob

Whoops! I see you are from NEW England. But some people will argue that it is worth the trip to merry old England to get one!;)
 
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Ronh,

What is the reason 8x32 SE has 3D-effect than other binocular ? Or does by default, porro bins has this effect than roof ?
 
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Not just the SE but any porro prism bino. Supposedly it is because the barrels of a porro prism bino are further apart at any given IPD than a roof prism bino. I think "stereoscopic" effect is more descriptive than "3D". Frankly, it is one of those "features" I never notice in practice unless I do an A-B comparo. Even then I am not sure IF there is a difference that's exactly what effect I am seeing. Lot's of reasons an image can appear dull/flat.
 
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