IIIf focusing woes

[n5jrn]

So, I have a Leica IIIf which I determined earlier this year consistently focuses a shorter distance than the rangefinder indicates it would. After trying without success to adjust the rangefinder myself, I sent the camera to DAG.

It came back still front-focusing. DAG claims he adjusted things to Leitz specifications, and I really don't doubt his word on that. What I suspect is that something odd is going on here; i.e. the issue affecting my camera is not one of those which normally causes focusing issues.

I don't think it's the lens, because both of my lenses consistently front-focus. I'd have to judge the odds of both lenses (purchased from different sellers) being affected by the same problem to approximately the same degree to be pretty low.

Anyhow, does anyone have any ideas as to what the root cause might be? I want to have the next time it makes a round trip to Wisconsin for adjusting be the last time.

 

[Nomad Z]

Which lenses are they?

 

[I Love Film]

Did you send the lenses to DAG with the camera?

It is entirely possible that two different used lenses are not focussing properly.

What do you mean when you say "front focussing"? Are the photos out of focus, or just the "indicator" is not correct?

Have you ever used a rangefinder camera before, and were those cameras focussing OK?

 

[Steve M.]

You'll definitely need to send the lenses w/ the camera this time. I have no idea what's wrong currently. It doesn't make a lot of sense, and unfortunately, on a screw mount camera you can't take the back off and ck focus w/ a ground glass.

 

[n5jrn]

I sent one of the lenses to DAG. The issue, however, is not that the two lenses behave differently, but that they behave basically the same: both focus in front of where the rangefinder says the focal plane is. That makes me suspect the root cause of the problem lies in the camera body and not the lens.

The two lenses in question are the 5cm Summitar and the 35/2.5 Color Skopar.

 

[colyn]

Have you used them? How do the images look?

 

[Blanc]

That sounds weird.

DAG as every other camera repair shop do adjust the camera flange to Leica specs using shims under the lens mount, this step is usually followed by a trip under a collimator to check if infinity is correct on film (if not, it means that either the rails or pressure plate are dead, quite unlikely to happen on a leica).

Then the rangefinder is calibrated.

What do you exactly means by focusing on front of where rf says the focal plane is?

 

[Paul Luscher]

The only other thing might be if the rangefinder's out of whack. But DAG has serviced my Barnack Leicas before and everything's come back fine.