Lens Mount Tolerances

[Dave Blackham]

Im wondering what the actual tolerances are when changing from one camera mount to another.

We can change the Red PL mount easily and re mount it repeatedly and have it maintain its back focus on one camera. My question is how are you guys finding changing between two mounts of the same make and type, is it repeatable and maintains back focus between two different mounts of same make and type or is it one mount collimated for each camera ? My second question is then changing between say a Red PL mount and other manufacturers mount, is the back focus adjustment same of does the camera back focus need re adjustment. I guess the real question is, What are the actual tolerances that mounts are made in the real world to maintain accurate repeatable back focus adjustment or should the camera be re adjusted when changing between two different types or when a mount is removed or the same mount re fitted.

[Stephen Williams]

Whilst it may be good enough to go to still mounts I don't believe it's good enough for PL to PL. Ideally should be within a couple of Microns, in the film days +/- 5 but from experiance 5 microns is a lot on Epic.

Im wondering what the actual tolerances are when changing from one camera mount to another.

We can change the Red PL mount easily and re mount it repeatedly and have it maintain its back focus on one camera. My question is how are you guys finding changing between two mounts of the same make and type, is it repeatable and maintains back focus between two different mounts of same make and type or is it one mount collimated for each camera ? My second question is then changing between say a Red PL mount and other manufacturers mount, is the back focus adjustment same of does the camera back focus need re adjustment. I guess the real question is, What are the actual tolerances that mounts are made in the real world to maintain accurate repeatable back focus adjustment or should the camera be re adjusted when changing between two different types or when a mount is removed or the same mount re fitted.

[Matthew Duclos]

Anytime you so much as loosen the screws on a camera (or lens) mount, you're likely effecting your flange depth.
This is why such fine adjustments are built into professional cinema lenses. Stephen is correct.
The smallest common adjustment made to a lens mount is .0005". That's half of a thousandth of an inch.
Simply removing and replacing a mount can severely effect your accuracy depending on the lens in question.

[Dave Blackham]

Anytime you so much as loosen the screws on a camera (or lens) mount, you're likely effecting your flange depth.
This is why such fine adjustments are built into professional cinema lenses. Stephen is correct.
The smallest common adjustment made to a lens mount is .0005". That's half of a thousandth of an inch.
Simply removing and replacing a mount can severely effect your accuracy depending on the lens in question.

Is that 12.7 microns ?

So I guess best practice is any time a lens mount is removed and refitted or screw tightened flange depth should be checked and if needed adjusted ?