[Kevin Purcell]

Useful to keep these numbers in mind when thinking about FOVs in the top end 80ish mm scopes

Zeiss 20x to 75x 120-48 feet/1000 yards
Zeiss 20x to 60x 129-60 feet/1000 yards

Swaro 20x to 60x 108-60 feet/1000 yards
Swaro 25x to 50x 138-89 feet/1000 yards

Leica Televid 25x to 50x 134-92 feet/1000 yards

Nikon EDG 20x to 60x 116-58 feet/1000 yards

Kowa 77mm/88mm 20x to 60x 115-55 feet/1000 yards

Zen Ray ED 2 scope 20x to 60x 115-60 feet/1000 yards

Vortex Razor HD 20x to 60x 117-60 feet/1000 yards
Vortex Viper HD 20x to 60x 110-50 feet/1000 yards

115-60 feet/1000 yards seems to be "the standard"

Interesting that Zeiss chose to go for slightly less FOV at the low end to get to 75x.

Feel free to add more: I'm interested in how values have changed historically. The classic Bushnell Spacemaster? Early Kowas?

[Kevin Purcell]

Baader doesn't spec any numbers but does give the AFOV. So an estimate for the Baader on the Zeiss based on the AFOV and magnification.

2*tan(0.5*AFOV)/M = FOV

Using Henry Links measured numbers for this eyepiece see

http://www.birdforum.net/showpost.ph...54&postcount=1

49 degrees AFOV @ 21x = 0.855211333 radians
72 degrees AFOV @ 63x = 1.25663706 radians

2*tan(0.5* 0.855211333)/21 = 2.4867801 degrees or 69 feet/1000 yards
2*tan(0.5* 1.25663706)/63 = 1.32151811 degrees or 130 feet/1000 yards

Baader zoom on Zeiss 21x to 63x 130-69 feet/1000 yards

Perhaps a little larger FOV than the Zeiss with slightly more magnification.

[henry link]

Kevin,

I just compared the TFOV of my two Baaders and the Zeiss 20-60x zoom. The Baaders don't turn out as you would expect because of pincushion distortion and because their focal lengths are off spec by different amounts. If we accept the Zeiss specs for FOV (129-60 ft/1000 yards) then this is the way the Baaders actually measure (based on 500mm focal length scope).

Mk I: 109.3-60 ft/1000 yards (21.8x-59.7x)
Mk II: 108.6-58.5 ft/1000 yards (20.3x-59.2x)

Henry

[Sancho]

Very useful comparison, Kevin. Thank you.

[Kevin Purcell]

Originally Posted by henry link

If we accept the Zeiss specs for FOV (129-60 ft/1000 yards) then this is the way the Baaders actually measure (based on 500mm focal length scope).

Mk I: 109.3-60 ft/1000 yards (21.8x-59.7x)
Mk II: 108.6-58.5 ft/1000 yards (20.3x-59.2x)

Thanks for the measurements, Henry.

A little bit lower than my estimates and my experience too.

As part of the checking out the ZR ED2 scope I compared the 85FL with Baader and Zeiss (they looked very similar to me but I didn't AB them) and the ZR ED2 which looked a little bit smaller by perhaps 10% (this is AB on the same (close) target with the scopes side by side).

10% difference in FOV seems to be about the smallest fraction I can say "They're close but this one is a bit smaller". Not glaringly obvious either but when you go back and forth against the same background you can measure (and feel) one is slightly larger than the other.

I'm also a bit biased as I tend to use a "wide" AFOV scope as my main scope: either my Promaster 65 ELX scope (with the Hyperion-like "Plano" zoom) or my Zeiss' with Baader or Zeiss zoom or my Pentax 65ED with a fixed PF12 (or other fixed wide-angle EP). My reaction to "normal" zooms is "that's a bit narrow".

[SEOW]

A useful post! But I believe the numbers for both the Swarovski and Leica wide field zooms are a bit inflated: Swarovski lists the field for its 25-50x zoom as 126-81 feet at 1000 yds at

http://swarovskioptik.com/en_us/prod...technical-data

and Leica lists the angle of view for its WA eyepiece as 2.35-1.6 degrees, which would be about 123-84 feet at 1000 yards:

http://en.leica-camera.com/sport_opt...pes/eyepieces/

I see that the incorrect specs are on Eagle Optics' website (and in the case of the Swarovski, on B & H's site, too)- looks like someone there simply took the figures of 41-28 meters at 1000 meters (the numbers given on Leica's site), and 42-27 meters at 1000 meters (the numbers on Swarovski's site), and converted the meters to feet, without noticing the fact that 1000 meters is a bit farther than 1000 yards, and so the scope's field is going to be wider out there.

[SEOW]

Or, rather, to revise my last sentence: "so the distance across the scope's field is going to be greater out there."

[Kevin Purcell]

Originally Posted by SEOW

A useful post! But I believe the numbers for both the Swarovski and Leica wide field zooms are a bit inflated: Swarovski lists the field for its 25-50x zoom as 126-81 feet at 1000 yds at

http://swarovskioptik.com/en_us/prod...technical-data

and Leica lists the angle of view for its WA eyepiece as 2.35-1.6 degrees, which would be about 123-84 feet at 1000 yards:

http://en.leica-camera.com/sport_opt...pes/eyepieces/

I see that the incorrect specs are on Eagle Optics' website (and in the case of the Swarovski, on B & H's site, too)- looks like someone there simply took the figures of 41-28 meters at 1000 meters (the numbers given on Leica's site), and 42-27 meters at 1000 meters (the numbers on Swarovski's site), and converted the meters to feet, without noticing that the fact that 1000 meters is a bit farther than 1000 yards, and so the scope's field is going to be wider out there.

Good catch, SEOW.

Quite a lot of companies seem to make this mistake when the European company just does the m per km spec. As others have pointed out here you just have to multiply by 3 to get the feet at kyard number. No fancy math needed

So to update the original list

Zeiss 20x to 75x 120-48 feet/1000 yards
Zeiss 20x to 60x 129-60 feet/1000 yards

Swaro 20x to 60x 108-60 feet/1000 yards
Swaro 25x to 50x 126-81 feet/1000 yards

Leica Televid 25x to 50x 123-84 feet/1000 yards

Nikon EDG 20x to 60x 116-58 feet/1000 yards

Kowa 77mm/88mm 20x to 60x 115-55 feet/1000 yards

Zen Ray ED 2 scope 20x to 60x 115-60 feet/1000 yards

Vortex Razor HD 20x to 60x 117-60 feet/1000 yards
Vortex Viper HD 20x to 60x 110-50 feet/1000 yards

115-60 feet/1000 yards seems to be "the (current) standard".

I think this also makes even the new Zeiss 20x-75x seem not too narrow even compared to the 2x Leica and Swaro EPs but the latter are still wider than at the same magnification than the Zeiss Vario.

[SEOW]

Aaaah, just multiply by three, thanks. Good to know.

Yes, the Zeiss seems very wide angle for having the magnification range it does. I'm saving my pennies for that or the Kowa....

[Kevin Purcell]

Originally Posted by SEOW

Aaaah, just multiply by three, thanks. Good to know.

Yes, the Zeiss seems very wide angle for having the magnification range it does. I'm saving my pennies for that or the Kowa....

John Russel pointed it out to me. I was sorry to say it hadn't struck me before. Sometimes the simplest solutions are the best.

The old Zeiss Vario is still wide. I'm sorry they gave up on FOV a bit to get the 75x.

[Parker]

Originally Posted by SEOW

A useful post! But I believe the numbers for both the Swarovski and Leica wide field zooms are a bit inflated: Swarovski lists the field for its 25-50x zoom as 126-81 feet at 1000 yds at

http://swarovskioptik.com/en_us/prod...technical-data

and Leica lists the angle of view for its WA eyepiece as 2.35-1.6 degrees, which would be about 123-84 feet at 1000 yards:

http://en.leica-camera.com/sport_opt...pes/eyepieces/

I see that the incorrect specs are on Eagle Optics' website (and in the case of the Swarovski, on B & H's site, too)- looks like someone there simply took the figures of 41-28 meters at 1000 meters (the numbers given on Leica's site), and 42-27 meters at 1000 meters (the numbers on Swarovski's site), and converted the meters to feet, without noticing the fact that 1000 meters is a bit farther than 1000 yards, and so the scope's field is going to be wider out there.

AFAIK this method of stating the FOV (So many meters at 1000 meters or Feet & yards) is expressed as a ratio so the extra distance in meters is irelevant. 42 meters at 1000 meters is the same as 126 feet at 1000 yards.

Cheers,

[SEOW]

Right, yes, 42 meters at 1000 meters does indeed express the same FOV as 126 feet at 1000 yards. But 42-27 meters at 1000 yards isn't the same as 138-89 feet at 1000 yards, which is the figure Kevin (and B & H, and formerly Eagle Optics) originally had down (at the beginning of the post) for the Swarovski 25-50x zoom's FOV. Someone somewhere presumably took the meters figure from the company and multiplied it by 3.28 to convert it into feet, which gives you 138-89- but that gives you the distance across the field at 1000 *meters*, not at 1000 yards, inflating the spec'd FOV.

Granted, my last sentence of the post you quote was quite muddled- tried to correct it in the next: no, the *field's* not wider farther from the scope (in the sense that the angle doesn't change), just the distance across it at that distance from the scope.

Hope that makes sense

Cheers,

SEOW

[Parker]

Originally Posted by SEOW

Right, yes, 42 meters at 1000 meters does indeed express the same FOV as 126 feet at 1000 yards. But 42-27 meters at 1000 yards isn't the same as 138-89 feet at 1000 yards, which is the figure Kevin (and B & H, and formerly Eagle Optics) originally had down (at the beginning of the post) for the Swarovski 25-50x zoom's FOV. Someone somewhere presumably took the meters figure from the company and multiplied it by 3.28 to convert it into feet, which gives you 138-89- but that gives you the distance across the field at 1000 *meters*, not at 1000 yards, inflating the spec'd FOV.

Granted, my last sentence of the post you quote was quite muddled- tried to correct it in the next: no, the *field's* not wider farther from the scope (in the sense that the angle doesn't change), just the distance across it at that distance from the scope.

Hope that makes sense

Cheers,

SEOW

Yes, I see where you're coming from now, Thanks for the clarification.

Cheers,