I have a Jupiter 3 lens that I plan to use on my Leica IIIf (which is currently away for a CLA). Mechanically, the lens seems okay - I took the helical apart and regreased it, although it wasn't too bad to begin with. While disassembled, I looked

I've taken apart and reassembled Jupiter-3s (for my SovCams [Zorkis & FEDs], am poor so no Leicas for me). I'm no expert on this, but it seems to me that the lens should be fine to use as-is. There's no adjustment on the lens that I know of;

I do plan to put it on and see how it goes - just want to have a plan in case something is out of whack.  
 
The infinity focus is a positive stop between the outer part of the helical and the lens barrel proper, but this whole assembly goes into th

I guess you could put marks on the threaded part before disassembling it, under the assumption that the lens was assembled correctly at the factory (or the last time it was serviced). Otherwise, I guess you're going to need a collimator to set the f

Hello Nomad,
the only way, as to my understanding, to check if the lens focuses correctly on infinity would be mounting the lens, setting it to infinity and check with a groundglass on the film plane if it focuses correctly. THe rangefinder is

Okay, I can see now why a ground glass screen is needed - the part of the lens that pushes against the RF cam might not be consistent between lenses, so the RF itself can't be used to check.

I thought that would have been obvious (that you can't use the rangefinder to check the lens' infinity focus), but maybe not.
 
In any case, while you can use a ground glass screen at the film plane to check infinity focus (that's what I us

It wasn't obvious at first because I was assuming that the ring that presses against the RF cam is positioned correctly (or within an acceptable tolerance) in every lens. In other words, position the ring correctly, and the lens is positioned correc

I think you're still confused. Setting the focus distance correctly has nothing to do with the rangefinder.
 
You're correct in saying that the RF cam should be at the same distance on every LTM lens (within tolerances). But this has nothing to d