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Airforce K20 camera

 
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kag00



Joined: 05 Apr 2010
Posts: 3
Location: NH

PostPosted: Mon Apr 05, 2010 7:56 pm    Post subject: Airforce K20 camera Reply with quote

Does anyone know what the field of view is (in degrees) of the standard lens that was used on the k20 camera during WWII.
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Dan Fromm



Joined: 14 May 2001
Posts: 1884
Location: New Jersey

PostPosted: Mon Apr 05, 2010 11:48 pm    Post subject: Reply with quote

The big question is whether the camera's gate's diagonal is 152 mm or 161 mm. The K-20's standard lens was 6 3/8", 161 mm.

152 mm diagonal means 50 degrees, 162 mm 53 degrees.

But that may not be what you're asking. The lenses were all f/4.5 tessars, should cover around 180 mm.
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kag00



Joined: 05 Apr 2010
Posts: 3
Location: NH

PostPosted: Tue Apr 06, 2010 12:21 am    Post subject: Reply with quote

Dan,

Thanks for your reply. What I am trying to determine is in the horizontal plane what is is the angle of view . I tought as the focal length gets longer the angle of field of view gets smaller, such as in a telephoto lens. I am working on a unique probelm where I have the aerial photos of a island and very recognizable features on the island and am trying to work back with the field of view angle how far away the plane was when it took the photo. Not sure this will work but I want to explore this idea.

Thanks

garry
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pv17vv



Joined: 22 Dec 2001
Posts: 255
Location: The Ardennes, Belgium

PostPosted: Tue Apr 06, 2010 4:03 pm    Post subject: Reply with quote

Sources on the www suggest the lens was 6 3/8.

According to Kodak specs ©1944, this means an angle of view of 35° x 43° when focused at infinity.
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kag00



Joined: 05 Apr 2010
Posts: 3
Location: NH

PostPosted: Tue Apr 06, 2010 4:08 pm    Post subject: Reply with quote

Thankyou, that is a start.
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Dan Fromm



Joined: 14 May 2001
Posts: 1884
Location: New Jersey

PostPosted: Tue Apr 06, 2010 9:44 pm    Post subject: Reply with quote

Georges, I calculate that a 162 mm lens covers about 41 degrees on 120 mm. 120 mm is the length of a 4x5 film holder's long side, but since the K-20 used roll film its gate may be a little wider. If so, the horizontal angle is a little wider too.

Cheers,

Dan
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bruiser



Joined: 15 Oct 2006
Posts: 259
Location: Northern NSW Australia

PostPosted: Thu Apr 08, 2010 1:26 am    Post subject: Reply with quote

Hi all,

Just dragged out the trusty K-20 and without pulling the whole thing apart it is very difficult to get an accurate reading of the gate size.

Trying to measure things from the back, which is obstructed by the vacuum plate and film feeding mechanisms, gives a reading that seems close to 160mm + or - about 5mm. Not too scientific!

Maybe if someone has a repair manual it might give the gate size. Or, even better, if anyone has an original negative shot with a K-20 and can pass on the measurements.

Just to add a little more confusion the lens on mine is an Ilex Paragon Anastigmat of 163mm focal length.

Cheers,
Bruce
http://graflex.coffsbiz.com
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Dan Fromm



Joined: 14 May 2001
Posts: 1884
Location: New Jersey

PostPosted: Thu Apr 08, 2010 8:24 am    Post subject: Reply with quote

Bruce, the War Department bought lenses, to specification, from a number of makers.

USAF continued the practice, with a twist. It sometimes bought lenses made to a design, e.g., Metrogons and 38/4.5 Biogons, from the low bidder, sometimes to a specification (focal length, maximum aperture, and coverage), e.g., three quite different lenses for the KA-16.
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peruchin



Joined: 26 Jul 2010
Posts: 1
Location: miami

PostPosted: Mon Jul 26, 2010 5:51 pm    Post subject: specs Reply with quote

According to Kodak specs ©1944, this means an angle of view of 35° x 43° when focused at infinity.
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pv17vv



Joined: 22 Dec 2001
Posts: 255
Location: The Ardennes, Belgium

PostPosted: Mon Jul 26, 2010 7:20 pm    Post subject: Reply with quote

©me...

BTW what is the angle of view of a dog's a**hole ?

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