I bought this SOM Berthiot 20mm f1.9 lens assuming it was a c-mount, but it is much smaller with an elongated screw mount. Can't figure out what type of mount this could be.


Here it is compared to a regular c-mount lens:



The lens in the picture is either a Bolex 8mm/9.5mm or 16mm format motion film camera.

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  • I agree, I have the same type of lenses for a 16mm camera (Pathé Webo) only the ones of the 16mm camera are a C mount. These also seem to be a D mount perhaps? Perhaps they can be mounted on a modern DSLR? – MicroMachine Oct 18 '15 at 1:17

Lens is simply missing the back half. It's not a mount, just a broken lens.

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It's smaller than 8mm d-mount. Looks like Lytar 5.5mm.

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This "auxiliary" type lens screws into the front of a "standard" lens

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  • 4
    It is? What lens thread would it attach to? If it's an auxiliary lens, why does it have aperture control and an aperture scale, as well as a focus distance scale? – Please Read My Profile Mar 15 '17 at 18:48

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