Adjusting a rangefinder that is good with some lenses

[john_s]

I'm wondering if my M6 bodies need adjustment, or perhaps I'm being too fussy.

The basic problem is: my old M6 focusses my 50/1.4 ASPH perfectly at infinity and also at 2.5m which is a distance I use a lot. My old Summicron 50/2 and new Summarit 75/2.5 also focus just about perfectly at infinity and 2.5m.

My Summicron 35/2 (ver 4) and 35/1.4 ASPH and Zeiss 25/2.8 all focus perfectly at infinity but they all front focus quite a bit at 2.5m. The 35/1.4 ASPH has had a trip to Solms where they did some adjustment (maybe very little) and it still seems the same to me. All lenses were bought new and have had a very gentle life.

My tests have been done with tripod, ISO=25 film and cable release. I have repeated them several times consistently. My later M6TTL is very slightly different but basically the same across all lenses.

My question is: is my problem that the bodies need adjustment? But I don't want the focussing of my 50/1.4 to alter. Can a body focus 50mm lenses and longer well, but at the same time the shorter focal lengths not at all well? If it were only one wide lens that front focused, I would suspect the lens. But three, all bought new?

 

[mfogiel]

To check the situation, you should perform a focus test at close distance (1m) - here's a little help how to do it:
http://photo.net/learn/focustest/

This way you will see what the situation is among the lenses, then you could test the same lenses on a different body for comparison and see if there's any difference - if so, maybe you have a body problem, but if anything, most likely the problem could be with the RF accuracy.

 

[john_s]

Mfogiel, thanks for the link.

I have done such a test at 2.5m with a similar (but larger) target, actually several times. The results are consistent and quite clear: with 6 lenses and two bodies.

The 50/1.4 and 50/2 and 75/2.5 are close enough to be called excellent.

The 35/1.4 and 35/2 and 25/2.8 are all front focusing by about 30cm.

I have sold the 35/1.4. The 50s and 75 I use the most.

I don't want to risk upsetting the focus of the 50/1.4 by having the camera adjusted, unless I'm sure that the focusing of the 50/1.4 will not be made worse. If I can't get the 35 and 25 to work I will consider living without them. I do have a manual focus Nikon SLR and 28/2 which is a completely problem-free solution, even though it's not as nice to use as the M6.

 

[ferider]

In case of doubt it's a problem with the lenses.

What strikes me is that your longer lenses work fine, the wider ones not. Your camera is definitely OK if it can focus the 50/1.4.

Are you sure you use the center of the patch for your test shots ?

If yes, I would send off the non-working lenses to DAG. 30cm is a lot of front focus.

Roland.

 

[Bill Blackwell]

If your lenses focus at infinity it's not the camera. Your lenses can be recalibrated to focus more accurately.

Once I got an M8 I discovered that about half of my lenses - including a 35mm Summilux, a 35mm Summicron, and a 50mm Summilux - needed to be adjusted. They were sent to DAG one at a time until they all focused accurately.