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C mount to EF adapter

Steve Williams

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I purchased a c-mount to EF adapter on whim just to see how it would perform. I've read mixed reviews on this forum about people using adapters. My problem is that the adapter doesn't seem to thread into the mount as nicely as I would like. I can get about 3 solid turns on it until it feels that it might strain the threads on the camera. Comparatively, my camera lens that came with the camera has no problem threading into the mount.


I tired out my canon lens's and was surprised to see that they performed almost as a macro lens. they appeared sharp, but I couldn't adjust the focal is only 3 to 4'. I used a 50 and a 85mm for my test.


I'm guessing this is due to the fact that I didn't rotate my adapter all the way into the mount. It looked like that I had about another 2cm to go until it was fully installed.


here is the adapter I purchased from Amazon:



any thoughts?




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How can it have 2cm more to screw in when the C mount thread only looks to be about 5 or 6mm long?


The fact your lenses are only focussing at close distances is because they are sitting too far away from the film plane, as you suspected.


Usually it's things like the back of the adapter being too wide and hitting something on the camera before it has screwed all the way in, or the thread being too long and hitting a surface inside the camera C mount. Could also just be a dodgy adapter, but Fotodiox is usually OK. If you can take measurements you might work out what is preventing the adapter from screwing all the way in.

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Thank you guys for the reply...


Pavan - I'm using the pro8mm version of the BL4008.

Dom - you're correct, I should have said 1-2mm. The thread count looks the same and the adapter appears to be the same size as my lens. I have a belt grinder at work, so i might try to take the adapter down a thread and see if that fixes the problem.


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From the 4008 user manual:


Use of non-automatic lenses

1. Standard the 16 mm lenses "C" mount lenses

Over and above the lenses especially designed for the Super 8
format, the 4008 ZM 2 camera will accept any object lens de-
signed for 16-mm work (C mount: extension 17.52 mm (11/16"),-
thread 25.4 mm (1") - max. thread length 3.8 mm (.15").

2. Stili-camera lenses

Most interchangeable 24X 36 miniature camera lenses can be fitted
to the Beaulieu 4008 ZM 2 by means of intermediate adapter rings.

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Jean-Louis, thank you for that information... I measured the circumference and the threads, everything looks to be the same. Still I can only get about 1 full turn on it. I cut down the threads a bit at work and it still doesn't fit onto the camera correctly.


Does anyone have any recommendations as far as a mount goes? I'm looking for a c mount to EF. I have searched google and this thread, but haven't come up with any model numbers or brand names. Any suggestions would be greatly appreciated.



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You should be able to screw that adapter in about 3 turns until it bottoms out on the baffle of a 4008. If the thread was too long (ie longer than 3.8mm) and you filed or ground the adapter mount down, make sure you clean the threads of burrs.


Check that there is no other damage to the adapter threads - all it takes is one thread ridge to have been impacted, to have mushroomed or folded over and it won't screw in properly.

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Hey Dom...


I'm guessing that one of the threads must have been damaged.... although they looked fine to me. This baffles me, I've measured it in every way possible. It's the correct length and same thread count... I took it down about 1mm in a belt sander and it still got hung up in the same spot. I'm about to purchase another, maybe a different model this time, and just hope for the best....

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