Why 12 by 50 shows more than 10 by 30? (1 Viewer)

[Ted Y.]

I just compared two binoculars, one (10x ) with
FOV 105 m @ 1000 m
the other (12x) with
FOV 95.6 m @ 1000 m

However, in practice, the 12x shows more broadness.
I validated this at 50 m and at 300 m.

Why?
The field of view (FOV) is not a measure of the broadness? If no, what property is important when buying binoculars?

 

[fazalmajid]

Well, clearly one of the specs is incorrect

 

[William Lewis]

Very strange, when you say compared do you mean measured the actual width you could see field stop to field stop, i.e with a measuring wheel? We're the bins mounted?

 

[Ted Y.]

Very strange, when you say compared do you mean measured the actual width you could see field stop to field stop, i.e with a measuring wheel? We're the bins mounted?

I kept a fix station and observed the number of visible cars parked (and fractions of a car). The "count" was lesser with the 10x.
Someone else observed this and today I had the occasion to confirm it is so.

The FOVs are from specifications.

 

[William Lewis]

Specifications as Fazal suggested must be incorrect in that case. The only other confounding factor could be wearing glasses if the bins didn't have sufficient eye relief to view the complete field.

 

[elkcub]

I just compared two binoculars, one (10x ) with
FOV 105 m @ 1000 m
the other (12x) with
FOV 95.6 m @ 1000 m

However, in practice, the 12x shows more broadness.
I validated this at 50 m and at 300 m.

Why?
The field of view (FOV) is not a measure of the broadness? If no, what property is important when buying binoculars?

By rough calculation, the 10x has a 6.57 deg. real field, and a 65.7 apparent field (i.e., retinal projection). The 12x has a 5.98 deg. real field and a 71.8 deg. apparent field. The retinal projections differ by 6.2 deg in favor of the 12x, so it should be perceived as having a somewhat "broader," i.e., less narrow, view.

The apparent field of view (AFOV) is the answer to your question.
Ed

 

[Ted Y.]

The apparent field of view (AFOV) is the answer to your question.

I will try to understand this, beyond the formulas.

 

[henry link]

I thought AFOV was the answer too, until I saw you were counting more cars lined up across the field of the 12x. What binoculars are these?

 

[Ted Y.]

Can the results be false because of a wrong IPD or wrong utilization of the binoculars?

 

[elkcub]

Yes, procedurally you should be viewing monocularly to make this technical evaluation. Otherwise, when viewing binocularly and depending on the IPD setting, the non-overlap areas may allow you to see more with two eyes than with either eye alone. If you think about it, the same can be said for normal vision without binoculars. The total field of view is always greater with two eyes than with one — which is one of the advantages of having two eyes.

Ed

 

[CharleyBird]

Would the two binoculars be the Canon 10x30 IS and Nikon Action EX 12x50 ?

 

[Ted Y.]

The binoculars are:
from Canon, 10 x 30 Image Stabilization II
from Vortex Optics, Viper HD 12 x 50

 

[kimmik]

If this turns out all correct, reminds me of camera megapixel specifications once upon a time - the “raw megapixels” is always higher than “effective megapixels” and was used to sound better. Maybe the IS buffer zone is the missing fov

 

[lilcrazy2]

Since the FOV in your first post seems correct for both the Canon and Viper, it would seem that there are two possibilities.
1. The 6.0* 105m FOV listed for the Canon is wrong
2. You are having trouble seeing the field stops for the full FOV on the Canons. Possibly due to some kidney beaning or partial blackouts obscuring the field edges? The objective ends of the IS binos are certainly a different animal as well as setting the IPD.

 

[Binastro]

Usually Canon FOVs are accurate.

In fact the 18x50 field is 3.85 degrees not 3.7 degrees.

Are glasses being worn?

Otherwise it suggests the Vortex field is bigger than stated.

Or the Vortex magnification is actually 11x and the eyepieces are somewhat wider than stated.

Canon magnification is usually accurate.

Many binoculars have wrongly stated magnification and wrong field sizes.

Regards,
B

 

[Binastro]

Further to above.

With an unstabilised binocular, particularly 10x and higher, the hands are not perfectly still.
The field is slightly larger because of hand movement and persistence of vision means this is not noticed.

Binoculars should be tripod mounted for measurement and one eye used, by capping one side of the binocular.

I find that Leica, Canon and Zeiss accurately state fields and magnification.

B.

 

[Binastro]

I notice that the Votex Viper HD 12x50 is listed as IPD 65 to 76mm.
This may be a mistake or typo.
But if correct then someone with less than 65mm IPD cannot set it correctly.

From memory.
Canon 10x42L 6.5 or 6.55 degree field.
Nikon EII 8x30 8.85 degrees.

Leica 12x50 Ultravid 5.75 degrees.

Minolta Standard MK 7x35 11.05 degrees.
Minolta Standard MK 10x50 7.65 to 7.8 degrees.

VisionKing 5x25 14.8 to 15.4 degrees 15.8 claimed.

Celestron 8x30. 6.7x 27

Conquest HD 10x42 6.65 degrees.

Bushnell 4x21 actually 3.5x21 field 18.5 degrees .17.2 degrees claimed.

6x24 Amplivid 12.2 degrees.

6x24 Komz 12.2 degrees.

5x25 Foton ~12.1 degrees.

12x45 Komz 5.4 degrees.
8x30 Komz ~ 8.5 degrees.

5x25 Bushnell. Actually 4.4x.

B.

 

[pat mitchel]

Binastro- vortex viper 12x50 specs IPD- 59-75mm per the vortex specs (website) Regards, Pat

 

[Mark9473]

The apparent field of view (AFOV) is the answer to your question.
Ed

Not if the test is counting how many parked cars are in view, as the OP has said.

 

[Trinovid]

Not if the test is counting how many parked cars are in view, as the OP has said.

Except that we don't know that, and it would have been more useful for the conversation at hand if the OP hadn't disappeared without addressing this point, and I hope he will at least give it a shot one more time using elkcub's experiment.