Flange Depth and Pellicle / Beam Splitter Reflex systems

[Evan Walsh]

Hoping one of the camera technicians on the forum can chime in on this because my googling hasn't brought me any answers. 

I'm familiar with checking and adjusting flange depth on film cameras with spinning mirrors via a depth gauge kit. 

I'm trying to understand what the procedure would be for checking flange depth in a camera system that uses a pellicle / beam splitter for their reflex design, like a Bolex or certain Mitchell reflex cameras.

Situations where a depth gauge would not be able to go directly from mount to film plane.

Thanks!

 

 

Edited February 13, 2023 by Evan Walsh
grammar

[Dom Jaeger]

It’s similar to modern digital cameras where you also can’t use a mechanical depth gauge - you have to optically measure it using a test lens that is perfectly calibrated. 

With a reflex Bolex you can actually measure the distance from mount to gate with the front removed using a micrometer, measuring from the outside rather than using a depth gauge, but because there are variations in the thickness of the prism (a tolerance value the Bolex repair manuals describe), you actually need to use a calibrated test lens and a collimator to check and set the appropriate physical flange depth.

 

 

[Evan Walsh]

Ah I figured that was likely the case, thanks Dom!