Graflex.org

kag00 · Joined: 05 Apr 2010 Posts: 3

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

Dan Fromm · Joined: 14 May 2001 Posts: 2165

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.

kag00 · Joined: 05 Apr 2010 Posts: 3

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

pv17vv · Joined: 22 Dec 2001 Posts: 255

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.

kag00 · Joined: 05 Apr 2010 Posts: 3

Thankyou, that is a start.

Dan Fromm · Joined: 14 May 2001 Posts: 2165

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

bruiser · Joined: 15 Oct 2006 Posts: 260

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

Dan Fromm · Joined: 14 May 2001 Posts: 2165

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.

peruchin · Joined: 26 Jul 2010 Posts: 1

pv17vv · Joined: 22 Dec 2001 Posts: 255