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Field of view vs magnification (1 Viewer)

Generally I think that modern binoculars have pathetically small fields of view.

Hi,

the problem is that building binoculars with afov beyond 70 deg to a current standard of edge quality and eye relief needs a complex eyepiece with a fairly large eyelens. The field stop and thus most other lenses plus the prism assembly also need to be fairly large due to the tfov requirement.

When this is done, you get the Nikon WX 10x50 - Nice wide afov, great quality but size, weight and price are shocking. Even the WX 7x50 lost a bit of afov in order to fit into the same form factor.

The old 6x and 7x super wide angle bins usually had very short eye relief and the edge quality was abysmal - how did the stars look at the edge of field when measuring the star separations in your Minolta - could you refocus to get pinpoint stars at the edges?

Joachim
 
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Hi Joachim,

Firstly, I cannot even use many modern binoculars because the eye relief is so excessive for me there is no support for the binocular from my face resulting in blurry images. It doesn't matter how good edge stars are if they are blurred by movement.
Secondly, I get blackouts with these.

The Minolta 7x35 edge stars are sufficiently good to take accurate separations using the mid point of the stars approx. I take several measurements till I am sure.
Also hand holding a binocular gives a larger separation than bracing a binocular. The 11.05 degrees is braced.
No eye swivel or slightly off IPD. Both of these give larger fields.

The edge stars with the Minolta 7x35 improve with refocus but are not pinpoint stars.

The Visionking 5x25 is stated as 15.8 degrees. The most I could get was 15.6 degrees. But 14.8 degrees easily and more if I centred my eyes carefully. The 15.8 degrees probably needs eye swivel.
It really is a shame the Visionking isn't made by a top maker to high standards with the latest coatings.

I use the Foton 5x25, which is super sharp but only 12.2 degree field.

As long as the edge stars are reasonable, large fields are useful to me.

The Canon 18x50 IS has very good edge stars and a measured field of 3.85 degrees. Very good flare control.

The Swift HR/5 8.5x44 is 8.26 degrees. The problem with this binocular is glare and ghosting, but it is my instantly available binocular. The earlier Swift 8.5x44 have somewhat larger fields but are unnecessarily heavy for me.

I have several 10x50s from 7.5 to 7.9 degrees true field, but the light pollution is so bad I don't use them anymore.

The Leica 8x32 BA is not wide field, maybe 7.8 degrees but beautifully free of ghosting and glare.

I don't get wow factors from any binoculars, except maybe the Zeiss 20x60S. But here the edge stars are completely out of focus because of a curved field. These binoculars are of near astro quality. I wrote to Zeiss asking them why the field is so curved, but typically Zeiss they did not reply to this sort of question.
It separated 6.5 arcsecond double stars compared to 8.5 arcseconds for the Canon 18x50 IS. Someone with better eyes would do better.

The 12x45 Russian binocular gave me a wow observation. Seeing a brightish star disappear when occulted by Titan. Then reappearing in mid occultation as the stars light was bent though Titan's atmosphere. Disappearing again and finally fully back into view. But the wow factor was the event not the binocular. Titan was not seen during this event.

The only wow factors I got were from telescopes.
M81 and M82 near the zenith with 12.5 inch Dall Kirkham. Saturn with this scope.

The Orion nebula with 20.5 inch Newtonian.

The wowist event was unaided eyes, the all sky halo display with multiple circles arcs etc. Just too much to take in.
No binocular needed.

Regards,
B.
 
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I don't know what all the fuss is about as 7x binoculars were available with 13 degree fields also, years ago.
Generally I think that modern binoculars have pathetically small fields of view.
Exactly... I suppose the fuss is coming from those of us who want a wider field and better sharpness than those old binos had.

Well, Tenex, there is a 7x50 with a 563 ft FOV - the Nikon WX.
I've been watching the bargains thread for some time now for a good closeout deal on those. But if WX can be considered the no-compromise ultimate, couldn't we have some practical option somewhere in between?
 
Nikon could make something between the EII 8X30 and the WX 10X50 but why would they, there is no real demand for it, no real profit...although I would like to see something with a wide field of 9-10 degrees with 10X and center focus that is less costly than the WX, I don't think it fits in with Prostaff 3, Action Extreme, etc.

Andy W.
 
Hi,

the WX 10x50 shows how big eyepieces for that kind of afov, good edge performance and eye relief will be. Scaling it down to 10x40 will still make for an instrument quite a bit north of the 1kg mark and thus not very popular either, at least not for birding.

You could of course loosen the requirements for edge performance and eye relief - this will make smaller EPs possible, but then we get close to the E2 8x30.

If you want wider true fields than the E2's 8.8 deg without going very big, you'll have to look for 7x or below magnifcation.

Joachim
 
My neighbour has a Russian surveillance binocular which I estimated has a 110° reasonably flat view, if you could actually get your eyes close enough to the huge eyepieces to see it. Although this is a 15x, as an 8x it would have a 720ft@1000yard view, or 820ft at 7x. Each prism weighs about 2kg (~5 lbs). Makes the Nikon WX look like a pocket model. ;)

David
 
The serial number on the one in the photo is low at N.16.

I looked through one of these in the daytime, possibly in Tring, but it was not something I wanted because of the low magnification.
They usually came on a tripod or pillar mount.
Sold as Guard binoculars.

There is also a 20x110 or possibly 25x110.

There is a rare much larger version, I think, but I never saw one. Maybe 12 element eyepieces on the large one.

Arthur Frank of Charles Frank offered me the Fortress of Malta 6 inch binocular, by Ross probably.
He wanted £250 late 1960s, but I didn't have the spare cash, and anyway I prefer large telescopes.

There are also large refracting binoculars from Czechoslovakia, Japan, Germany, Italy, Russia, U.S.A. and probably others.
Up to 300mm aperture.

There are also large amateur built versions.

Regards,
B.
 
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