Calibrating the RF on bottom loaders?

[hamradio]

So, I didnt think the barnacks had the lens mount bolted to the body shell, since the later leica IIIc and IIf I worked on had the lens mount in the shutter crate.

Then I worked on a canon IIf. And now a Zorki 5. The lens mount is bolted to the body shell, making the usual trick of a focus screen in the film gate impossible, since you can't have a lens mounted and peek through the film gate at once.

How in the hell does one calibrate the RF on these things, short of either buying an autocollimator or using a second body shell with a hole cut out for a focus screen? I don't like the idea of throwing a known good body/lens combo on a tripod, focusing to a set distance, then throwing that lens on the test camera and adjusting the rf to correspond with those settings. Seems (and is!) super tedious and not that accurate. Is there some trick I'm missing here?

 

[Sid836]

On these cameras you first measure the accuracy of the film plane to mount distance and shim it accordingly. Then you adjust the view finder/rangefinder just like the others for close and infinity focus.

 

[John Shriver]

You can use a micrometer depth gauge to measure flange to pressure plate distance. But you need to know the distance from the pressure plate to the focal plane without film in the camera. Or you insert a plate of glass as "film."

Alternately, put a mirror at the film place and use an autocollimator, and a lens known to be collimated.

Note that you also want to be sure that the lens mount is parallel to the film plane.

 

[rick oleson]

In other words, you're not missing anything - it's a bit of a PITA.