75 Lux / M9 calibration drifted off: camera or lens??

[simonpj]

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A couple of years ago I sent my M9 and 75 Lux to Solms. They repaired and recalibrated the 75 Lux and returned the M9 RF to factory specs. For a year or so after that I used the 75 Lux at f1.4 and f2 with no problems, but during the last year I've had increasing problems with back focus.

 

It now focuses pretty reliably between 1 metre and 3 metres - and is also ok at infinity - but in the 5 to 15 metre range that I use for the stage / theatre work that I do it is back-focusing so that the actual plane of focus is 3 or more metres behind where I've focused. This is ok as long as I'm using un-cropped shots, but where I need to crop in on performers on stage it's clear that the focus isn't where it should be.

 

Will it be the M9 rangefinder mechanism or the lens that has drifted off spec over the past two years? I've had some success adjusting the RF cam in the past, but am reluctant to get out the allen key for fear of doing more harm than good. But if it's more likely to be the RF mechanism than the lens I'm happy to have a go at tweaking the adjustment. Or is it the 75 Lux that goes out of calibration? In which case I'll need to send it back once again to Germany.

 

Other lenses, including the Noctilux, haven't seemed to drift out of calibration over the past two years. But maybe that's because their focusing calibration isn't as critical as the 75 Lux? On the face of it, it seems more likely to me that the M9 RF mechanism would drift out of calibration, than the 75 Lux...

 

Any wisdom gratefully received!

 

Simon

[davidmknoble]

Unfortunately, that happens. I would send both to Leica for a CLA and matching. I am getting ready to send 5 lenses and 2 bodies for the same. Tough to wait, but worth it when the wide open f/stops nail the focus.

 

I use the MP more with an old 50mm lens and shoot lots of film while I wait...

 

Best of luck!

[adan]

It is far more likely to be the camera than the lens. The camera has moving parts that can drift over time (focus cam and all the levers between it and the RF prism). The lens parts are pretty well locked together with a helical. The only way they can get out of true is a physical knock that dents the rear surface (brass rim) that touches the camera's roller connection.

 

The only exception would be the very early 75s (separate lens hood style) with a push-rod connecting the lens helical to the camera. These are spring-loaded to "follow" the lens helical in the outwards direction, and the springs can weaken, or the push-rod "rails" can get sticky with old lubricant and dust, which means the push-rod fails to follow the helical and delivers inaccurate positioning to the camera RF.

 

However it is still good to send Leica both items, since your 75 is likely the most critical lens for focusing. A camera adjusted for the 75 exactly should work fine with any other lens - any difference being covered by DOF.

[simonpj]

I did in the end decide to risk taking an allen key to my M9's cam follower using instructions posted on this forum in 2010 (here: http://www.l-camera-forum.com/leica-forum/leica-m9-forum/122176-m9-coincidence-infinity.html)

 

After moving the infinity focus back a very small amount I've managed to cure the back-focusing on the 75 Lux perfectly, whilst retaining perfect focus at all distances on the Noctilux.

 

I'm happy and relieved!