Mitchell 35R3 backfocus.

[Paul Bruening]

Hey fellas,

 

I've got this Fries 35R3. It has changeable lens boards as many of you know. I'm running Nikons on it. I bought it with the PL mount on it. It came with a small selection of home-made lensboard shims fashioned from what looks like Kodak 85 gel sheets. I can probably scrounge up a decent shim material to replace the plastic. I can fashion the shims. My issue is this:

 

I don't have a collimator. I'm dead broke and can't ship the unit to AbelCine like I know I should. What's a good way to do the check on the flange focal distance? I've got good dial calipers. But I'd need to check it optically. Could I simply put a ground glass on the gate in the film plane? Wouldn't the shortest lens wide open give me the most critical test? Is it correct to assume that there should be no variation between the viewfinder and the ground glass?

 

What do you think of this info? http://lavender.fortunecity.com/lavender/5...ollimation.html

 

Do you have anything to add or vary?

 

Of course, the lenses are already collimated. So, I'm just adjusting the lensboard shim.

[Tim Terner]

Hi Paul, came across this page, dont know whether it might be helpfull to you http://www.geocities.com/leafshooter/collimator.htm

[Paul Bruening]

Hi Paul, came across this page, dont know whether it might be helpfull to you http://www.geocities.com/leafshooter/collimator.htm

 

Good info. Thanks Tim.