Modified c-mount lens adapter

P

pomoville

Well-known member
Some C-mount lenses are too wide at the back flange to fit in the M4/3 c-mount adapter. This adapter supports lenses that have been especially modified to M42 thread to get around the width limit. If your c-mount lens is one of the ones that can't screw in all the way to the c-mount flange, you can have it modified apparently. It also accepts c-mount lenses unmodified.

http://en.wikipedia.org/wiki/Flange_focal_distance

The quality and precision of these adapters for FF depth is all over the place. Actual rear element to sensor focal distance for lenses varies too, but should be consistent to the FF distance standard. The better adapters are cut about 1/2mm less than the reference depth to insure infinity focus for the lens, which then may need to be shimmed out a little to get it right. The not so good ones don't hit the mark and won't focus at infinity. Since you can't adjust back focus on the camera, (something that most video cameras allow), it is a hit or miss prospect. You can have the lens collimated to match your camera by an optical shop, but that may defeat the cheap lens approach using c-mounts.
 
Last edited:
I know what an m42 mount is, but based on the description that doesn't appear to be the primary function of the adapter. Rereading it, my understanding is that the intention is to replace the c mount with an m42 mount in order to correct the flange distance -- the m42 input on here definitely wouldn't focus properly with an m42 lens, as its much too short.
 
i'm have exactly that adapter. if for m42 you have extension rings 7+14+21(mm) - then use adapter+21mm and focusing of m42 optics will be as needed
 
You must log in or register to reply here.
Back
Top