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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

FOV decisions (1 Viewer)

B

black crow

Well-known member
I've noticed many upper middle end and some upper end priced binoculars have a smaller FOV than many middle priced binoculars. I guess that is because most upper end binoculars pride themselves on not going very soft out to the edge of the view.

However for birding and such it would seem to me that even if softer a larger FOV would be desirable. I mean once I've located my target I don't focus much on the edge of the view but I sure notice difficulty birding with small FOV binoculars. I have Zen 7x36 with 477 ft FOV and it's my go to for birding. Pretty soft out at the edge but it's worth it to me. Even long range I like the expansive feel of that larger but softer FOV. It's one reason I don't often consider more expensive binoculars and I can't bring myself to pay top dollar for an alpha.

What's your opinion on this?
 
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i dont know fov from easter bunny except what i have read here but i assume more fov means more likelihood of actually picking up the bird? i often see a bird, lift bins to eyes then spend time moving binos around to find the darn thing, often too late. if the edge is where it appears i shift my body slightly. i also guess widercfov means just shifting eyes would be enough to identify rather than move glasses or body. i cant see anything wrong with your thinking. it is what i would want as it allows speed on target and less movement both of which are important in watching any creature.
 
BC,

I don't know how optical designers go about their work, but I think we can dissect some of the key decisions.

Say the target is a 8x with a 70° AFoV. With an ER of 20mm means the eye lens needs to be 28mm across, but 16mm ER would be 22.5mm. There is a cost, weight, and quite possibly minimum IPD choices in that decision. Conventional eyepiece designs trade field curvature, astigmatism, CA and other aberrations as the FoV increases, generally increasing in complexity cost and weight with increased FoV. A wider angle of view needs larger prisms, again increasing cost and weight. It is possible to manage the size and weight and reduce aberrations with increasingly sophisticated optical complexity. A Smyth lens in front of the focal plane will increase increase effective focal length allowing smaller prisms and reducing CA. A simple flat lens, for example, after the focal plane will flatten the view but increase other aberrations, which in turn need additional correction. Moulded plastic aspherics have been used, but with seemingly mixed results. Most wide field, lower priced models I've seen do have significant levels of distortion, which some will tollerate more than others. Even at the top level with the most sophisticated designed it is necessary to trade one distortion for another which would not be universally acceptable. All of that means if you want a low distortion wide view binocular it is going to be big, heavy and expensive. The Nikon WX models for example.

No easy solution that I know of, but if users chose spectacle frames with a short vertex (eye to lens) distance it would make the designer's job a lot easier, and we might see more smaller, lighter and cheaper wide view options. I recently discovered that one of my frames gave me a vertex distance of 8mm, which might make a 12 or 13mm ER possible. My optician tells me 10mm would work for most users, and should make 15-16mm ER acceptable for most, but he also sold some fashion frames which produced an 18mm vertex which would need at least 22mm ER. I certainly grumble about the cost of my glasses, but they are still a fraction of the price of an alpha. It's a shame I never saw the ZenRay 7x36 (16.8mm ER). The Monarch 7 8x30 with 15.1mm ER is pretty useful. Surely there is room for something better still?

David
 
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The Zeiss SF has a wide FOV, is a premium glass, but high $$$$$.
It is also LONG, almost as long as my UV 10X50, but you get that wide FOV.
As David points there are going to be sacrifices to get that wide FOV, one way or another.

Funny story about the WX, I had an order into Nikon since the Beginning of the year, an EDG 8X42, well they were getting impatient with me, about not being to fill the order after all the EDG line was recently archived. So I get an e-mail that says perhaps you could change your order to a new HG, (I already have one), or how about change it for a WX, I lost my Coffee.

A.W.
 
jape said:
i dont know fov from easter bunny except what i have read here but i assume more fov means more likelihood of actually picking up the bird? i often see a bird, lift bins to eyes then spend time moving binos around to find the darn thing, often too late. if the edge is where it appears i shift my body slightly. i also guess widercfov means just shifting eyes would be enough to identify rather than move glasses or body. i cant see anything wrong with your thinking. it is what i would want as it allows speed on target and less movement both of which are important in watching any creature.
Click to expand...

FOV = FIELD OF VIEW

You just have more of the scene to find the dang bird in and he has less a chance to hide. I love a close up of a bird in my 10x but it doesn't happen nearly as often as it does in my 7x. Of course the more you practice the better you get at it. Over time you can get pretty good at looking and bringing the binos to your face and seeing what you are looking at but it's still challenging going after those jumpy little ones that never seem to sit still.
 
typo said:
BC,

I don't know how optical designers go about their work, but I think we can dissect some of the key decisions.

Say the target is a 8x with a 70° AFoV. With an ER of 20mm means the eye lens needs to be 28mm across, but 16mm ER would be 22.5mm. There is a cost, weight, and quite possibly minimum IPD choices in that decision. Conventional eyepiece designs trade field curvature, astigmatism, CA and other aberrations as the FoV increases, generally increasing in complexity cost and weight with increased FoV. A wider angle of view needs larger prisms, again increasing cost and weight. It is possible to manage the size and weight and reduce aberrations with increasingly sophisticated optical complexity. A Smyth lens in front of the focal plane will increase increase effective focal length allowing smaller prisms and reducing CA. A simple flat lens, for example, after the focal plane will flatten the view but increase other aberrations, which in turn need additional correction. Moulded plastic aspherics have been used, but with seemingly mixed results. Most wide field, lower priced models I've seen do have significant levels of distortion, which some will tollerate more than others. Even at the top level with the most sophisticated designed it is necessary to trade one distortion for another which would not be universally acceptable. All of that means if you want a low distortion wide view binocular it is going to be big, heavy and expensive. The Nikon WX models for example.

No easy solution that I know of, but if users chose spectacle frames with a short vertex (eye to lens) distance it would make the designer's job a lot easier, and we might see more smaller, lighter and cheaper wide view options. I recently discovered that one of my frames gave me a vertex distance of 8mm, which might make a 12 or 13mm ER possible. My optician tells me 10mm would work for most users, and should make 15-16mm ER acceptable for most, but he also sold some fashion frames which produced an 18mm vertex which would need at least 22mm ER. I certainly grumble about the cost of my glasses, but they are still a fraction of the price of an alpha. It's a shame I never saw the ZenRay 7x36 (16.8mm ER). The Monarch 7 8x30 with 15.1mm ER is pretty useful. Surely there is room for something better still?

David
Click to expand...


What? What did you just say to me?

OK I did sort of understand some of that. (I'm reading Bill's book) I think that a wider FOV is well worth a softer edge for very practical reasons. I'd rather pay extra $ for more of the scene than a small amount of increased detail in the center and edge of the view that I usually wouldn't notice or can't due to eye age and mental decrepitude.

If I ever do buy something more expensive it will very likely be the Kowa Genesis 8x33. Somehow for half the price of most alpha glass they give stunning optical detail along with 420 ft FOV. I really want one but that still seems a lot ot pay for one binocular. They do also have a PERFECT fit for my face and all the rest. (I'm trying to get a free one by writing this ad for them) I'm pretty sure within the next month I'll get over my SNOBBISHNESS and ELITISM, get down off my superiority high horse and buy this alpha binocular. 8-P
 
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BC,

I might put a greater emphasis on centre field performance, but I do like a wide view too. As long as I get about a 55°AFoV that is reasonably sharp I'm not bothered by astigmatism, CA or vignetting beyond that range. I suppose user comments, including here, have led to an increasing customer demand flatter views, sharper edges and increased eye relief. It has a consequence in size, weight and price, but also contributes to other user complaints about blackouts and distortion. Just suggesting another path.

The Genesis 8x33 (15mm ER) ticks a lot of boxes, but then, so does the new Swaro CL (16mm ER). ;)

David
 
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I like a FOV above 400 feet but I don't like real soft edges. If the edge is too soft I notice it and it bothers me but it doesn't have to be Swarovision sharp either. I do tend to like the flatter fields as in the SV, SLC, SF or Nikon MHG with sharp or pretty sharp edges.
 
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Same here, In an 8x I usually don't have much interest until I see the number 400+. 420 really works for me.

Here's something most may not think about or need but in the winter I get SADD. Looking through binoculars on a winter day with some sun really seems to help my mood and the large FOVs does this best for me. I'm sure this is in part an emotional thing along with any physical benefit. In the winter you will often find me reaching for my Zens and looking for open sunny landscapes with lots of reflected sunlight.
 
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