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Though I am no expert on European 35mm cameras, I believe the Ektra was the first 35mm to have interchangable film backs.‡ These were precisely machined to mate with the camera body and were held in place by two knurl-headed machine nuts, operated from the front of the camera body; these engaged threaded studs in the camera back. Each back ($55 ca 1941) had a dark slide operated by the slider visible above on the bottom of the back. In the locked position, it was not possible to remove the back, though with the machine nuts loosened and the dark slide still locked, some light would enter the space between the back and the camera and that film frame could be fogged; a good but not perfect design. Also above on the right is the rapid folding rewind crank.



	Though I am no expert on European 35mm cameras, I believe the Ektra was the first 35mm to have interchangable film backs.‡ These were precisely machined to mate with the camera body and were held in place by two knurl-headed machine nuts, operated from the front of the camera body; these engaged threaded studs in the camera back. Each back ($55 ca 1941) had a dark slide operated by the slider visible above on the bottom of the back. In the locked position, it was not possible to remove the back, though with the machine nuts loosened and the dark slide still locked, some light would enter the space between the back and the camera and that film frame could be fogged; a good but not perfect design. Also above on the right is the rapid folding rewind crank.

	The four bright pads that you see on the face of the cylindrical parts of the back that house the film engage mating pads on the camera body. Final machining of these calibrated the exact lens/film distance. Here you also see the keyed mechanism that drives shutter winding and the toothed shaft that operates the takeup reel. ‡ If you know of this feature on an earlier camera, send me a note at the Comments adddress below.
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