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Field of View

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Gerry Atric View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gerry Atric Quote  Post ReplyReply Direct Link To This Post Topic: Field of View
    Posted: July/17/2016 at 08:40
Would a binocular field of view be linear ?

100 yards FOV @ 1000 yards
10 yards FOV @100 yards
1 yard FOV @ 10 yards

Is it a good thing to measure actual FOV at 10 yards ?

Would the FOV depend on distance c/c of "barrels", person "A" could get a different FOV than person "B" pending distance between the eyes ? Does an out-of-focus binocular render a wider FOV than a focused binocular?

Some questions that has popped up.....

Gerry Atric


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Dogger View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dogger Quote  Post ReplyReply Direct Link To This Post Posted: July/17/2016 at 10:31
My understanding is that it is linear.

I believe a simplified formula is degree of FOV divided by 180 X pii X radius

I have no idea if the interpupillary distance has any effect.

Ilya will have the definitive answer.


Edited by Dogger - July/17/2016 at 10:50
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anweis View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote anweis Quote  Post ReplyReply Direct Link To This Post Posted: July/17/2016 at 14:59
when reported or listed as a distance at 1000 yards or 1000 meters, it is linear. Imagine a triangle, the binocular is at one corner, the distance  between the other two corners is the linear field of view. The larger the angular field of view, the longer that linear distance would be. Meaning, a wider angle means a longer line opposite to that angle, and more of the world is in view. 
Binoculars are listed sometimes with their angular fields of view, like 7* or 8* degrees or so. The wider the angle, the longer or wider the linear field. 
For a pleasant to use instrument, you want wide angle, to avoid tunnel vision and the feeling that comes when looking through a tube. 
Apparent field of view is calculated by multiplying magnification with angular field of view. An 8x binocular with 8* field will have a very nice and wide 64* apparent field of view.  The same 8x binocular, with a 6* field, will have an angular field of view of only 48* and would feel restrictive, like looking through a pipe.  
I like a minimum of 60* apparent field.  
I have owned and used a few wonderful 7x binoculars, but they only had 7* field of view, or less. Regardless of how many linear feet or meters that was, and how sharp and bright the optics, the apparent field of only 49* was unpleasant to me, like looking through a tube. 
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koshkin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: July/17/2016 at 16:57
FOV in feet scales linearly with distance.

To convert between angular and linear FOV, take tangent of half of the FOV angle multiply it by distance of interest and double the result.

For narrow FOVs, you can use the angle in radians instead of taking a tangent, but 8 degrees is not that narrow.

As far as IPD goes, it does not really have an effect on FOV.

ILya
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Klamath View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Klamath Quote  Post ReplyReply Direct Link To This Post Posted: July/18/2016 at 15:28
Measuring at ten yards is fine.  If there is a distance available for long distances, you can double check that way.

At ten yards I tape a cloth tape measure to the wall and set the binocular on a tripod.  I then place the center of the tripod as close to exactly 30 feet (10 yards) as I can.  Place one edge of the fov at the end of the tape and see what measurement you can see at the other.  Convert the inches to feet.  That will give you feet at 10 yards.  Easy math to convert to 1,000.  There will be some uncertainty about what the readings are depending on how much edge distortion there is.

There are 52.5 feet to the degree


Edited by Klamath - July/19/2016 at 22:00
Steve
"Everything that can be counted does not necessarily count; everything that counts cannot necessarily be counted". William Bruce Cameron

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Gerry Atric View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gerry Atric Quote  Post ReplyReply Direct Link To This Post Posted: July/19/2016 at 00:23

Thank´s for all the help fellas.

Better to ask and get my hazy thoughts confirmed than go out and make a mistake....

Bought a new 8x42 binocular on recommendation and I´m very happy with it´s performance, there was one review claiming that FOV was narrower than the advertised 8.52 degrees - I just wanted to see if I could reach a result of either 8,52 degrees or the reviewers FOV of 8,11 degrees.

The result was close to the reviews 8,11 degrees but I´m still happy with the purchase, this bino is substituting my old Hensoldt 7x50 ( half the weight and bulk) or the Hensoldt 8x30.

Gerry Atric


Edited by Gerry Atric - July/19/2016 at 11:10
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