Jump to content

B4 mount won't lock on lens the full rotation


Mike Krumlauf

Recommended Posts

For whatever reason this lens won't lock into any B4 mount correctly. It gets about halfway and feels like its locked but im feeling like its not suppose to stop here. I tried both on my F900 cameras and a Varicam i use to have and the bayonet lock lands in the same position on every camera. Should I be worried about this? What can i look at on the back of the lens to see what might be causing this? The registration pin maybe?

 

 

 

 

post-74343-0-81837700-1537465391_thumb.jpg

Link to comment
Share on other sites

  • Premium Member

I don't know the possible issues with B4 mounts specifically, but as a rule with breech lock designs like PL, there are a few possible things causing the lock ring to stop short.

 

Check the thickness of the flange wings of the lens mount with vernier calipers, if they are a little over-size (compared to other B4 lenses) the lock ring will lock off early. As long as the lock ring turns enough to cover at least half of the lens mount flange wings, it should be OK. Sometimes manufacturers make parts that are a little out of tolerance.

 

Check the lens mount for any signs of damage or deformation, a burred edge or protruding screw head, etc.

 

Check the throat of the camera mount to see whether it has a chamfer, and whether the lens mount has an undercut at the corner that mates with it. If the lens mount for instance has been machined so that the rear protruding part that locates inside the camera mount throat meets the seating flange with a small slope, rather than a precise right angle or an undercut, it can foul on that edge and sit a little high.

 

Check that the locating pin is not damaged or too large for the mating cut out in the camera lens mount.

 

Check that the rear part of the lens isn't protruding too far and hitting something inside the camera mount before properly seating.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...