Back focus help w/ Allstar A mount

[Stiv Brown]

Looking for any assistance with back focus. I'm using a RED One MX, with an Allstar A-mount and Zeiss C/Y primes.

I've got the RED's back focus ring pushed all the way back toward the sensor, I cannot get any further, and it seems the primes still need to get a hair closer to reach lenses registered back focus. It's also very difficult to get the a mount to turn this far back.

Any advice or assistance is greatly appreciated.

Thank you.

Stiv

 

[Jay Kim]

If your camera's back focus is way off, first check your A-mount adapters on the lenses. Since A-mount adapter has two pieces(outer ring with mount & inner barrel for different mounts) I would flip the outer ring and test it.
If it doesn't work, locate a PL adapter for A-mount and Red Focus to check the flange depth of the A-mount on the camera.

 

[Dave Blackham]

Id Agree with Jay. Check the A mount lens rig is on right way round. I inadvertently did this once. Switched it round and then worked fine. Hope this is the solution please let us know how you get on.

 

[Stiv Brown]

Wow I feel dumb. Spot on guys. Problem fixed. Thank you!

 

[Dave Blackham]

I dont think you are dumb it bit us first the same way so we are all in the same place here.

While you are at it check the A mount with A to PL adaptor for flange to sensor distance with a collimator on your camera. its usually not same as a Red PL mount and camera may need adjusting.