Hi Nordleadx,
Thanks for sharing. I can understand how you feel and I fully sympathize with you what you are going through.
I am a camera dealer and I do not speak only for repair technician. I love cameras and I am photography enthusiast as well. Hence, I will "try" to explain things on both angles. Hope after reading this, it will help all of us understand better the risks and fun playing with these classical beauties.
Starting from the first lens incident that you came across. I understand that the lens that you bought from eBay was a 50/f1.2 Canon LTM mount. You subsequently sent it to a camera repair technician located somewhere in the east part of Singapore for a CLA. The lens came back clean & lubricated, but you suspected that there is a back focus problem. You even bought a new adapter from me thinking that it could be the adapter issue. But the problem persisted.
From my limited knowledge as a camera dealer, lens that fast, usually at f1.2 do exhibit back/front focusing characteristics. Reason being that it is almost impossible to make a lens to be 100% coupled with the RF body in a mass production environment. Considering the fact that the lens was made even before the repair technician was born (more than 50 years ago), manufacturing standards and tolerance level were different, QC were different. And having live through so many hands and generations, being opened up & dissect so many times, it's not difficult to understand that a f1.2 lens do not perform like a new summilux any more. Even with the 50mm/f0.95, for it to work on a M mount body requires some machining and not many people are trained to do it. I have seen 0.95 machined to mount on a M6 and after I tried on my M6 body with film, when I developed, what I got was only blur image, even I was very sure my focusing was spot on.
My point is, rangefinder cameras images through the viewfinder are NOT What You See What You Get (WYSWYG) images. It works by the logic of coincidential image. That is why, I have always told my customers NOT to drop their cameras, because the RF level is VERY VERY sensitive. By factory standard, we can only calibrate to infinity focusing and vertical alignment. Even the camera is calibrated, the lens needs to be calibrated as well to be fully coupled as a whole.
The lens calibration is more tricky. In all cases, we calibrate lenses to infinity using collimator or manually. But this can only calibrate to infinity and make sure that at infinity focus, our lens is tack sharp. What is not done is making sure the scale on the lens barrel match corresponding to the actual distance. This is often assumed 100% accurate on the manufacturing side and the lens design is good. Can you assume this to be true for a 50 year old lens?
As focusing on RF is by mechanical level, even if the focusing patch matches and it is spot on, we cannot assume that the image is in focus. If shooting at f2.8 or f4, the depth of field would often cover the inaccuracy. But when shot wide open f1.4, f1.2 or f1, one will definitely find some back focus or front focus issues. Unless you are talking about lenses machined to very high precision. The CV 35mm/f1.2 is one such example. Most of the copies I have come across usually do not have this problem.
Having said that, the first technician you can across, have done the work of a CLA. Cleaned, Lubricated and Adjusted to infinity focus. Don Goldberg from USA quoted the amount and claimed that "len will be checked and made sure it will not have focusing issues and ready to be use" it probably meant that at infinity focus it is calibrated. To check the back focus problem, one needs to mount the lens on a digital body, take a few test shots at various distance with the help of a scale to determine how much it is back focus. After which adjust the lens again. But do note that if the lens is calibrated to correct the back focus issues, what will happen to infinity focus? Logic will explain that infinity focus will also be affected as it is shifted! Hence you cannot have both worlds at the same time.
I suspect that when the lens was being built, the Canon f0.95 & f1.2, they were meant to be 100% coupled with the Canon 7 series bodies. Fortunately or Unfortunately they are in LTM mount and today people adapt them to use on the M8, which we see result immediately. I don't think people 50 years ago would care so much on back focus front focus issues as they should me more accommodating on manufacturing tolerance. Even for Konica Hexar lenses, on Leica M bodies, some of them do exhibit pretty serious back focus/front focus issues too.
To the other readers who plan to buy lenses from eBay or from the second hand shops, do have the right expectation that lenses of such vintage do not perform as well as the lenses today. If they do, then you have strike lottery. If you expect precision lenses, then get a new summilux or noctilux or my Nokton
then you can be sure that if the lens do not perform to your expectation, it's still under manufacturer warranty.
I saw your f1.2, it's really a gem. If I were you, I will not send it to another operation to dissect it again. Since it's so clean and well oiled, use it and appreciate it. I think we tested on the R-D1 the other day at the coffee shop, yes, it did show some back focus issues. To me, it's acceptable and I have seen summilux that were worse than yours... and you can imagine a used summilux is at least 4 times more expensive than what you have paid for this lens.
Hope we have learn from this incident and calibrate our expectation correctly
