Auteur: François Besson
Date: 11-06-2007 09:21
C'est un peu un monologue, mais voici quelques éléments trouvés sur le sujet:
source : http://pws.prserv.net/varney/20cms/cameras.htm
AERIAL CAMERA TYPES K-17, K-18, K-19B, AND K-22
The 20th did nearly all its aerial photography with two camera types: the K-17 and K-18. The K-17 was a 9" x 9" format (negative size) mapping and reconnaissance camera. It had three major components: a body, containing most of the mechanics and controls; a detachable magazine for 9 1/2" wide roll film; and a lens cone, with 6", 12", or 24" focal length options. The K-17, like the other three cameras in this section, was developed and built by the Fairchild Camera and Instrument Company.
The K-18 reconnaissance camera differed markedly from the K-17 in construction. The K-18 body and lens cone were built as a single unit housing a 24" focal length lens. Film format was 9" x 18".
A handful of night photography missions were flown with K-19B cameras in June and July 1945. The K-19B had a 12" lens, was of 9" x 9" format, and had a shutter that was operated by an attached photocell unit. The K-17, K-18, and K-19B all employed between-the-lens shutters.
The squadron was provided an abundance of K-22 cameras, but never used them for a combat mission, having found them "...unsuitable for mapping and not entirely satisfactory for reconnaissance..." (Interestingly, the F-7A's and B's were designed for a pair of K-22's to be mounted at the camera bay split vertical station.) The K-22 was a 9" x 9" format camera with lens cone options of 6", 12", 24", and 40" focal length. Unlike the others, its shutter was a focal plane type.
All these cameras were normally operated from a 24 VDC electrical source, but could be manually operated by a hand crank and shutter lever (the K-22 was electrical only). Each was fitted with a connector for an intervalometer that fired the camera at an interval set by the aerial photographer.
All used a vacuum applied to the film magazine to flatten the film surface before each exposure.
While these cameras were normally clamped into mounts, a pair of handles and a viewfinder could be fitted to K-17's and K-18's for hand-held operation. What "hand-held" meant is subject to interpretation, as these cameras were not lightweights. With a 200 foot roll of film, the A-5 film magazine used with the K-17 weighed 30 pounds. A complete K-17 with 12" lens cone and a full magazine weighed about 55 pounds. With a 24" lens instead of the 12", the weight climbed to near 75 pounds.
All four of these cameras used 9 1/2" wide Eastman Aerial Safety film. Film emulsions were Class L and Class N. Class L was the "normal" high-speed panchromatic film. Type N was labeled extra high-speed panchromatic, and was used for night photography in the K-19B's. The common lengths of film rolls were 200 feet and 75 feet. (Two hundred feet was the maximum film load for an A-5 or A-5A magazine. The A-7 magazines used with K-18 cameras held a maximum of 75 feet.)
K-19B with A-5A film magazine. Photocell unit is attached.
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Format: 9" x 9"
Lens: 12" f.l. - f/2.5 - 41.11° x 41.11° view angle
Shutter: Between the lens
1/25, 1/50, 1/100 second
Control: Light-activated via photocell
Cycle time: 3 seconds, frame-to-frame
Magazine: A-5 or A-5A - 200 feet - 250 exposures
François
Les éditions du courlis déchaîné
Aux aimables cornichons
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