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 p.1 #5 · p.1 #5 · Back focus on Leica lens - can I fix it myself? | |
Sorry, this ended up being a bit long....
How is infinity focus? If the lens is set to the physical infinity hard stop, is the rangefinder patch out of alignment? Is the photo sharp (the 50 Lux ASPH is surprisingly good wide open at infinity)? If you live view the same scene and best focus is not at infinity, but slightly pulled back from the hard stop, I'd be suspicious of the lens (be sure your infinity target truly is far away). If the infinity hard stop is sharp in live view, then it still doesn't rule out the lens, as it could be a problem with its RF cam being slightly out, but it could also be the body. Is the back focus consistent at all distances? Does the body of the lens feel tight, or is there noticeable play in it - i.e. ability to slightly twist the front relative to the back, or to push/pull it slightly? How is the camera with the 35 Cron in the same situation?
How good is your eyesight? Do you wear glasses and if so, do you use them with the camera? If not, it might be worth trying a viewfinder diopter correction lens. I'm slightly nearsighted and don't normally wear glasses and found this to be of noticeable help. As you mentioned, a 50/1.4 will be quite demanding of precise focus and the diopter correction made the rangefinder patch that much clearer, for me.
If you have the time, it might be worth a trip to Leica Mayfair if only to try any lenses they have available for in-store demo as a comparison against your 50. If there is also consistent back focus with their lenses, it's the camera.
A few observations I've made about the M240 and 50 Lux ASPH:
Leica apparently requires the M240 to be checked and calibrated on a specific device that is apparently very expensive and quite rare. As a result, most Leica locations are not able to do tasks such as rangefinder calibration for the M240 in-house. This is what I've gleaned from several in-person visits to Leica US, based on what the CSR told me ('big, expensive, special purpose machine') when we discussed the possibility of same day adjustment. FWIW, Leica US have the machine and were able to do it same-day, though depends on the technicians. The flip side to the inconvenience of having to send the camera to Germany if this can't be done locally, and the inevitable slow turnaround, is that the camera seems to always come back perfectly RF calibrated, based on my experiences (I've had to have this done more than once because I was unlucky to have the camera knock against something fairly hard, which threw out the RF). I suppose you could do the fix yourself, but at this point it's unclear whether the problem is with the lens or the camera, so best to first sort that out. Also, if the camera is still under warranty, I'd rather have Leica do the work, despite the time you'll be without it.
The 50 Lux ASPH seems to be very demanding of everything being properly adjusted and tightened. It has a floating element system, so I would be reluctant to advise something like shimming it unless it's physically focused past infinity at the infinity hard stop and the mis-focus is consistent across the entire focusing range. Its rangefinder cam is more complex than other lenses, which means it could be slightly out at one or more points along the cam. This would result in good focus at some distances, but off at others.
My copy is also the silver version and has had to go to Leica several times now for tightening after the lens body loosened with a noticeable wobble. This loosening is eventually enough to throw out the floating element focusing system, causing image degradation, most noticeably wide open (images look softer/glowy than they should, yet clears up considerably at f/2). My worst experience with this resulted in the lens being quite loose and the rangefinder being totally off. I've just sent it in again after noticing a degree of back focus, but also more glowy than normal wide open results and uncharacteristic detail smearing in the outer image areas. If you're getting very sharp wide open focus with live view (no significant glow), then your lens probably doesn't have this problem. But it's something to keep an eye on, apparently (based on feedback from a couple others who had the same problems).
Unfortunately this is part of the 'Leica experience' in that when everything is perfectly tuned, it's great. When not, it's a fair amount of hassle and inconvenience, primarily due to the long service turnaround times, to get it back into optimum form. My impression so far is that the combination of fairly high sensor resolution and working with fast lenses demands the utmost precision and accuracy of the system's mechanical parts for the best results. My expectation is that I'll probably be sending in the camera and probably also longer, faster lenses from time to time to have them fine-tuned.
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