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View Full Version : Do Leica M bodies ever front focus after shocks or service?


Dante_Stella
09-28-2017, 22:26
Has anyone ever had an M camera unexpectedly front focus across all lenses? I have been using them for 20 years+, and the only direction the RF has ever drifted off is in the direction of back-focusing, particularly when bumped.

Likewise, how exactly does Leica calibrate rangefinders? Every time they have repaired one of my cameras, it has come back with the focus calibrated such that lenses work wide-open (barely) and then back-focus at every other aperture. Are they using an APO lens to calibrate the cameras? Or do they just not care about smaller apertures on non ASPH lenses?

I know this is not my imagination because when these cameras come back, they don't work with any of my lenses, and the same master adjustment to the infinity setting makes everything work suddenly, whether a Nikkor from the 1950s, an M-Rokkor from the 70s, a Summilux from the 80s, a 35 ASPH from the 90s, or Konica and Zeiss lenses from the 2000s. It is not likely that 11 lenses would all be misfocusing exactly the same way and suddenly not with a small camera adjustment; it seems that the common denominator is in the body?

Or am I crazy here?

Ronald M
09-29-2017, 09:36
Garbage work I am sorry to say. The RF has 2 adjustment points, infinity and 1 meter. Your 50 is marked at 1 meter to accommodate.

I know 75 1.4 has focus shift which means it probably focuses at 2.8. Other f stops are not correct. I thought mine was soft open as did most people and I checked various samples. When I got digital I could see it front focused wide open .

RF has nothing to do with focus shift. Small stops are probably covering up error there if you fix infinity.

Leica had to adjust RF for digital because film is not flat and focus is not set at exact registration distance. With digital it has to be.

I suspect the calibration jig is set for digital and film cameras are now off. Do they have two setup jigs? New Jersey probably not. Germany yes and people are trained. NJ is a place that can not retain talent for reasons unknown to me. They have been known to farm out work.

I would send film cameras to DAG.

Dante_Stella
09-29-2017, 12:55
Yeah, most recently I had to have Leica fix my M240 because it had a displaced part inside the RF that DAG said he did not have the tools to fix (it's the thing that prevents patch drift when you move your eye). That was the only ill effect from my kids' getting ahold of the camera and dropping it, so paying $280 is not, in the grand scheme of things, terrible.
But this is the third time I've had Leica fix a 240/246, and it has always resulted in things being vaguely unsharp. Now that I have a LensAlign, it is very easy to see what is going on. Originally I thought it was the focusing rate adjustment, but it responds almost universally to an infinity adjustment. Maybe it's a very subtle rate error - but if so, it's so subtle that the infinity fix rarely turns up a distance/lens/aperture combination that does not work as expected.

The RF certainly doesn't have anything to do with it, but an aspherical APO lens (which I'm sure is what Leica uses to test) does not have focus shift the same way older or less corrected lenses do. So if they are setting for what is perfect for that lens at any aperture, they are disregarding everything else. There is also the issue that the field of focus is not flat on the sensor with older lenses.

I don't think that the problem is that the fixture is off for film cameras; it's that something changed in the way they align digitals between the M8/9 and the M240 that is resulting in these problems (from what I understand, they do it via a souped up version of LiveView in real time).

But the rest of the back focusing seems to be that there is something in there that has some kind of tension or screw lash that gets released when there is a shock. The eccentric in the roller arm does not always turn in a consistent direction from camera to camera to influence closer versus further, so it's not clear that it is the culprit.

jaapv
09-29-2017, 13:06
The difference between film-period and digital adjustments is solely that the tolerance has been narrowed, as film is more forgiving than a sensor.
Lenses that exhibit focus shift are normally adjusted to focus correctly wide open, unless the owner requests another aperture.