Elmer-M 50mm/2.8 on M10M

[Drmat]

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@herr that is good to know.  I would rather avoid paying for a repair on a lens I can return, but it is good advice, especially for those rare finds.  I am in Canada, so I am a bit hesitant to send an item across the border for a repair on account that both governments can apply duties seemingly arbitrarily, with no recourse :(.

[Jeff S]

1 hour ago, Drmat said:

@herr that is good to know.  I would rather avoid paying for a repair on a lens I can return, but it is good advice, especially for those rare finds.  I am in Canada, so I am a bit hesitant to send an item across the border for a repair on account that both governments can apply duties seemingly arbitrarily, with no recourse :(.

That was my comment... Herr was more interested in his cousin. There used to be two reliable repair options in Canada, both seemingly out of the business now (Gerry Smith retired)....

https://leica.nemeng.com/007e.shtml

Maybe someone here knows of another Canadian source.

Don Goldberg has fixed things for me that Leica NJ Service could not, quickly and inexpensively. For instance, for 90 bucks (including shipping), he made my 50 Summilux M ASPH focus like butter, after Leica could not, and It was back to me in a week.  Don’t know if he deals with Canada, but he’s easy to talk to or email... if only for your future needs.

Jeff

Edited June 12, 2020 by Jeff S

[Drmat]

@Jeff S  thanks!

[onasj]

On 6/6/2020 at 7:43 AM, onasj said:

Yes, actually!  My copy (black, 372xxxx) also front focused, especially noticeably at longer distances, and also could not reach infinity focus wide open.  I fixed the lens myself and it is perfect now, but it took quite a bit of effort (only worth it for a relatively inexpensive lens if you enjoy such projects). 

The flange bayonet ring (the silver ring that mounts to the body) is unusual for this lens. It has a machined shallow region at smaller radii (closer to the center) that is thinner than the rest of the flange—obvious both by feel and by the fact that it has been machined down and shows the color of the brass, rather than the chrome plating of the rest of the flange.  You can easily remove the flange by unscrewing the six rear screws with a small Phillips screwdriver.  The purpose of this shallow region is to allow a small circular ridge in the rest of the lens to properly mate with the flange without bumping into the flange.  This circular ridge rotates as the lens is focused.

I realized that both the flange and the flange’s shallow region were not shallow enough by a small fraction of a millimeter, which kept the optical cell from being as close to the flange (and thus as close to the sensor) as needed to reach infinity focus.  Incidentally, if the flange’s shallow region is not shallow enough, then the circular ridge will also rub against the flange as you focus the lens, causing a stiffer focusing action.  In fact if you screw on a regular M mount flange onto this lens, you won’t be able to focus the lens at all because a normal M flange lacks the shallow cut-out region and is entirely flat on its backside.  This is why you can’t fix the infinity focus simply by sanding the entire backside of the flange down.

So fix #1 was to carefully sand down the rear of the flange and the shallow region of the flange to move the optics of the lens closer to the sensor.  I used a circular cutter to cut a piece of 300 grit sandpaper of precisely the diameter of the shallow flange region, mounted it with CA glue on a cheap third party flange I had lying around, carefully centering it, then mounted the resulting sanding tool into a cheap M mount rear lens cap.  Now I had a handheld tool that would perfectly sand down the shallow region of the flange to be a bit thinner simply by rotating the tool as I pressed it down on the flange’s backside.  Sanding the entire backside of the flange is very easy—I just rotated the flange on a piece of sandpaper taped to a very flat piece of polished granite (aka a countertop).  After a fair amount of careful sanding, with washing, remounting the flange, and testing in between, I could watch as the infinity focus wide open slowly came back.  One helpful tip that told me when there was no additional improvement to be had is that extending but not locking the lens’s end will also keep the optics slightly closer to the sensor than if you lock the lens’s end, so I kept sanding the flange and the flange’s circular shallow region until there was no additional sharpness benefit to not locking the lens’s end.  Once the flange was the right depth, I used micro mesh sticks (inexpensive, on Amazon) to progressively polish up the flange until it was very smooth—much smoother than the original state of the flange.

Fix #2: Now I had a lens that correctly reached infinity focus, but the rangefinder focusing was still off, causing front focusing when using the rangefinder.  This one was easier to fix: since the cam on the rear of this lens (the part that engages the rangefinder roller) is plain exposed brass and does not rotate, I simply sanded down the part of the cam that contacts the roller.  This part is easily identified as this is also the part of the cam that is closest to the deepest part of the scoop cutout on the flange of any M lens.  I used the micro mesh sticks starting with the coarsest 1500 grit and ending with the finest 12,000 grit, which left a polished finish quite a bit smoother than the original Leica cam!  I was careful to sand the cam lying on my back, keeping the lens inverted, so the metal dust would fall down away from the lens.  I wore a mask to avoid breathing in the dust.  I also covered as much of the lens as possible with blue 3M tape before sanding to prevent any metal dust from getting inside.  Again, I did plenty of testing as I proceeded to ensure I filed down the cam by just the right amount—a small fraction of one millimeter.

After both fixes, the lens now focuses to infinity and the rangefinder focusing is perfect.  Took a lot of time and effort but was a fun project.  I probably wouldn’t have tried it on a more valuable lens.

The fact that your 50/2.8 had the same problem as mine makes me wonder if it is more common than one would think.  The differences between the lens as I received it and the fixed lens are noticeable on a 24 or 40 MP sensor, but might not be that noticeable on film, instead just being attributed to the lens not being the sharpest.  When fixed, it is quite sharp wide open—not quite in the league of the best modern lenses such as the 50 APO or 50 lux ASPH, but quite good.

 

I just had the opportunity to test a more recent copy (#398XXXX) of the 50/2.8 Elmar-M and it does not have the front focusing problem that my older copy (#372XXXX) had before I fixed it.  So indeed if there was a systematic front focusing issue with some 50/2.8 M copies, Leica seems to have fixed it at some point between 1995 and 2004.  Another difference is that the newer copy had a much shinier (more polished) extendable center column than the 1995 copy, even though both lenses are in near-mint condition.