miscalibration of Leica lens at infinity

[blacktaped]

Hi all
two weeks ago, on my flight back from Lisboa (you can check photos from that week here ) I was playing with my Leicas focusing the vapour trails of a plane flying few miles away from mine, and found out that my summicron 50 doesn't align perfectly at infinity. At first I thought that it was a problem of my M2, then I noticed that the lens wouldn't align on my M6 too, whilst all my other lenses (a summicron 35 and an old elmarit 90) would align perfectly on both cameras. So I guess it is actually a problem of my lens and of my bodies. This was confirmed also by testing my lenses on an M8 of a friend of mine, where I could also check that this misalignment doesn't produce any big issue in terms of sharpness of far objects, since I can't tell the difference between far objects shot using my 50 and with my 35, at wide open.
First: is there any easy way to calibrate a lens focusing distance (i.e. something that doesn't involve collimating the cam)?
Second: would you actually do any fixing, since you can't really tell the difference in alignment?
By the way, the 50 seems to focus sharply and correctly at shorter distances, of course.
Thanks for your help

 

[Vickko]

Ouch. The infinity for the lens is governed by the cam surface that is ground onto a ring. What is happening is that the cam is not at the correct depth to set the cam sensor in the body to infinity. I don't know if the cam can be slightly turned, to achieve the correct depth. Maybe someone like DAG can adjust the cam.

So,
1. I don't know if you can calibrate the focus distance.
2. I know it's an annoyance; I might not try to "fix" the lens. If it is close, the DOF would take care of things.

...Vick

 

[blacktaped]

thanks Vic

 

[Melvin]

How far off is the rangefinder patch, a hair or a lot? The rangefinder is meant to be adjusted for a particular lens. I've had DAG CLA three of my cameras, he does an amazing job, but the infinity adjustment has never been on, I always just do that myself. My summicron is dead-on on my M2, a little off on my M5. If I wanted I could adjust my M5 so it was perfect. I think the Leica system is designed with this in mind, that you can tweak it.

 

[notturtle]

my cv 35 goes past infinity but focus is accurate on film throughout. Do a focus test (using a scale) to see if it actually affects images. If not I would leave it well alone until it needs something else doing (if ever)

 

[ampguy]

This is great for CV lenses if you can adjust this yourself or have done locally. The 75/1.4 Summilux infinity (and close) calibration procedure can only be done in Solms, not NJ or Canada.

Of course this can explain a lot of things, if you think hard.

 

[blacktaped]

Hi Notturtle, how do I do a focus test with a scale? Thanks for your help

The misalignment is about a hair thick, nothing really serious, but it is annoying, for example, to see a far away antenna being doubled in the rangefinder at infinity. Basically, the lens stops a bit before the end of the rangefinder arm movement, so I guess it is telling you that the right focus is not at infinity, but, say, at 200 meters...

 

[Sparrow]

Is this something that is impacting your pictures?

I can't remember ever checking alignment, a couple of times I've had to have it adjusted, but only when I made persistent miss-focus at closer ranges, I'd pop a couple of films through it and see how it goes, there's little of interest at infinity anyway

 

[Nikon Bob]

If you are having no problems with the sharpness of photos taken with the 50 at close and far distances on either camera, I would ignore the slight mismatch of the focusing patch at infinity. It may be annoying now that you have noticed it but if you try adjusting the camera for it you may get issues with the other lens.

Bob

 

[john_s]

...... Basically, the lens stops a bit before the end of the rangefinder arm movement, so I guess it is telling you that the right focus is not at infinity, but, say, at 200 meters...

If the cam of that particular lens is not in exactly the right location, it seems likely that the lens focuses properly at infinity because that's where the lens physically stops. It's probably just the rangefinder indication that is a bit out.

If you do a critical test at two or three metres and it tests ok I would leave well enough alone. I have several Leica lenses, mostly bought new, and two bodies (one bought new) and in critical tests they are all a tiny bit out. It doesn't affect my photos hand held, 400 speed film.

 

[blacktaped]

Thanks John, the point is that the misalignment is in the viewer of the rangefinder window, where the two images don't overlay properly. For example, if I point at a far enough antenna, it will appear in the finder as two antennas, very very close to each other. I must say that even in that case, I never noticed any big issue (the image at infinity was sharp enough even wide open, and there's nothing interesting at infinity anyway 🙂 ) and also, in the lens scale, in that case the infinity symbol falls between the F.2 range so it's always in focus; I shall follow most of the suggestions here and not to bother too much about it.
Moreover, the lens performs accurately in terms of sharpness at closer distances, so I guess I won't be worring too much about it.