Lens mount adapter on C-Mount Lens

Braxton Jennings · October 31

Hey everyone! I recently picked up a Berthiot Pan-Cinor 20–70mm lens, which I know is originally a C-mount lens. However, when I got it, I noticed it has another mount attached that I’m not familiar with.

After some digging (and a little help from ChatGPT), I got mixed answers—some say it might be a PL or Bolex mount. The box also says “Arri Zoom,” which just added to the confusion. I tried checking for set screws to remove the adapter, but none of my Allen keys seem to fit the threads.

Does anyone recognize this mount type? And if so, is it removable so I can get back to the original C-mount?

Thanks in advance for any insight!

Edited October 31 by Braxton Jennings

Braxton Jennings · October 31

another image of the lens.

Dom Jaeger · November 1

Looks like Arri Standard mount, for the Arriflex 16St. I don’t think it’s an adapter over a C mount, but it may unscrew to allow different mounts to be attached.

Zoom lens manufacturers often made lenses that could be fitted with different mounts. The Arriflex mount versions didn’t need the reflex dogleg that most C mount versions had.

I haven’t heard of a 20-70, are you sure it’s not a 17.5-70?

ChatGPT is wrong about specialised knowledge like this more often than it’s right. You may as well ask your Uber driver, though at least they will tell you when they don’t know something rather than just confidently make something up.

Simon Wyss · November 1

It’s the 17,5 to 70 mm. OP just saw the figures 20 and 70 on the scale plate. Yes, the lens rear is so designed that an ARRI bayonet sleeve can be fitted or a C-mount one or a Caméflex adapter, and so on. In order to change that, the lens needs to be partially disassembled for access to the screws that hold the mount sleeve.