75mm AA Summicron Infinity rangefinder registration

Just acquired a 75mm AA and at my normal viewing distance for infinity(400

yds), the 75 is perfectly in register with my M3, but just a hair out with my

M6(0.85) and slightly less with my M7(0.85). Dave at Leica NJ, says to do

anything they will want the lens/camera combination. I have both M3 RF lenses

and new ASP 35 1.4 and the 90 AA also and have not had this problem. I realise

that this is a mechanical calibration problem and that variances exist. I

don't see that it is worth the effort to return the lens to Leica for

adjustment to a specific camera body. Am I just encountering this sort of

thing for the first time or being too picky? Thanks for any information. -Dick

If your AA 90/2 is right on on all cameras, then the 75/2 AA is wired, it is wired that the infinity cam good on one but bad on another, while other lens are right on.

"I don't see that it is worth the effort to return the lens to Leica for adjustment to a specific camera body."

 

As you said...

Dan could you please restate another way. I have no idea what you're talking about re: "wired".

Try a more distant subject, for instance the moon, with all lenses and cameras and see if the problem persists. If so, and only then, there must be a problem either with all your existing cameras and lenses or with the new lens. In that case, there is in my opinion a much greater chance that it is the new lens that is faulty, so I would ask Leica whether they should not send you a new one.

I think Dan means "weird" not "wired"

The suggestion to check its infinity focus at something like the moon is most likely correct. However, I would take pictures of specific objects at known distances before I would consider that there was an issue with either the lens or the camera. I have several lenses that are perfectly in focus as long as I use the RF. They may be hair off in scale focusing, but that is a fact of life with most lenses because no two lenses are likely to be exactly the same focal length but if they are close they will be fitted to a standard helicoid mount. I would be particularly careful not to have anyone fool with the RF train as it is delicate and unless there is a definite error you can open up a barrel of worms if you try to change the adjustment. Do your measurements first and record them, then if there is a dichotomy with the actual pictures a competent technician is the proper party to consult.

I don't know what happened to my previous attempt to answer this query. Don't expect the calibrations on even the best lenses to be micrometer correct. Because no two lenses of the same formula rarely end up exactly the same focal length there is a good chance that some are going to end up at the large end of the tolerance factor. Your best bet is to set your infinity focus on some celestial body such as the moon and then take a series of exposures of known objects at measured distances (aperture wide open). Chances are that some discrepancy will show up in the nearer focus range, but chances also are that the DOF of the lens will compensate and there will be no real problem. I would hesitate to have anyone but the most skilled technician fool with the internal works of the RF. Leica lenses are closely matched to the slope of the focusing helicoid but the marks are applied with an engraving machine and minor errors are not unheard of. The proof of the issue is whether the measured objects focus correctly.

Shot a roll of Elite Chrome on the M6. When I had removed the film I tried the infinty registration agin and it was perfect. It was also perfect on the M7 and the M3!

The lens was brand new and the original progression for mounting was M6 to M7 to M3, with the registration getting progressively better with each camera it was mounted on, until it was perfect with the M3 originally. Took the lens and shook it but it continues to be in perfect register at infinity now with all threee M's. Strange? But I also feel better now! Thanks to all who replied.-Dick

Ed Rudolph , sep 18, 2006; 03:09 p.m.

I think Dan means "weird" not "wired"

yes Weird, sorry, I typed too fast and did not check it before I post.

Before you do anything drastic, why not run a roll through your camera and view the results. Often, minor discrepancies in the rangefinder view do not even show in photgraphs. Then, too, you can always stop down! Best of luck, Bill

I agree with Dan. It's not only weird, it's impossible (in that it defies logic). I'll explain. Since all cameras agree in showing correct infinity focus with the 90AA, then they are all calibrated the same. Since the 75 shows proper infinity focus on the M3, as does the 90, then these two lenses are in agreement. How then, can they not agree on the other two cameras?

 

Richard, I'm sure your observations are valid. Yet, there must be some explanation. Sherlock Holmes said, "When you have eliminated the impossible, whatever remains, however improbable, must be the answer." As an owner of three Leicas and various lenses, I think it's improbable that you made an error in observation someplace. Yet it seems that all your results cannot be true at the same time. So how would you feel about repeating your observations, perhaps with a truly distant target, like a TV tower at least 1 mile away; or with the moon? All observations to be made within a few minutes of each other, and with a fresh and rested eye.

 

After all, making repeated observations to verify results is a cornerstone of science.

I would be more concerned about its accuracy at closer distances. Shoot a roll with subject at 5 to 20 feet and see if they are in focus first.

"When I had removed the film I tried the infinty registration agin and it was perfect"

 

Richard, sometimes your eye position within the eyepiece can change the this registration. Make sure that your eye is centered in the viewfinder eyepiece, it could make the difference that you experienced.

Richard, I see I missed your second post. Looks like you've already done a second observation. Well, suspicions confirmed, at any rate. It helps to confirm Erwins Put's remark that the eye is part of the rangefinder's optical system, and one that is tired, or otherwise not sharp enough at the moment, can introduce error. Glad you sorted it out--another learning experience in getting to know one's cameras.