M9 and various lenses

[TonyField]

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With my M9 I have the 135 F4, 90mm F2, 75mm F2.5, 50mm F1., 50mm F1.4, 50mm F1.5, 35mm F2, and a 28mm F2.8.. Except for the 75mm 2.5, all lenses are "old" from the 1950-'s to 1980's.

 

With the exception of the 90mm F2 Summicron, all lenses focus perfectly wide open on a test target wide open with an easy-to-focus on test subject. Yes, things like the 50mm F1 and 50mm 1.4 do display focus shift when stopping down. All of this works as expected. The 90mm F2 Summicron (1970's vintage) however, displays a tendency to focus in front of the test subject. Yes, you could argue that the target is "just withing the permitted depth of field" --- but that says you are comfortable in having the wrong part of a subject's face in focus.

 

This is not (IMHO) operator error in that all of my testing is consistently repeatable.

 

The test target is a bent piece of white wire bent so that it is parallel to the film plane of the camera. The focus point is, of course on the wire. which is about 3.5 or 4 m away.. As you can see in the texture of the paving stones, the actual point of image focus is about 5 cm in front of the target.

 

I sent the lens to New Jersey for adjustment. They have replied that they cannot reproduce the problem in any way -- even on their MTF measuring equipment.

 

The have suggested that I send the camera to see if it is a camera issue. The camera was previously sent to them twice ... the second time (about a year and a half ago)they replaced the sensor do to classic M9 sensor issues. All of my lenses, except for the 90mm F2 Summicron work perfectly with the M9 on this (and other) test subjects wide open.

 

What is your advice on how to proceed? Sending the camera in would obviously take months of time delay. I could pick up a 90mm F2.5 or F2 to replace the old Summicron and avoid the problems. I could continue to use the ol lens as long as I keep it stopped down to F4 or so.

 

Help !!!

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[ajz]

Looks like your camera and it's film plane is at an angle...need 4x5 camera with adjustable film back! Just kidding .z

[tobey bilek]

If the camera works with all lenses except the 90, then the 90 is defective.

 

Send in the 90 or replace it. If it back focuses, add a shim . Be sure the last 4 digits of the serial are the same on the lens and scribed inside the lens mount. They are supposed to be a matched pair.

[Lenshacker]

Is the focus off at all distances?

 

Is this the version of 90/2 Summicron that has a removable head?

 

When stopped down to F4, does it still front-focus when used close-up?

 

If the focus is off at all distances, and the lens is front-focusing, then the optics need to be moved in closer to the image plane. For removable head: Make sure the optical head is in all the way, and that the seat in the focus mount and lens is clean. I've cleaned out grease/grime before that made the difference. The Leica lenses do not typically use shims. But- you never know until you look. If there is a shim installed, try removing it.

 

If the focus is good at infinity, and only the close-up focus is off: the internal cam that translates focus to the RF cam is off. OR: the focal length is "off". In the case of the 5cm F1.5 Summarit, this was done by design to compensate for focus shift, the focal length of the 5 that I've disassembled were all scribed 51.1mm. When used wide-open,the lens front-focuses close-up, but is fine at infinity. The Summarit is optimized to be used at F2.8 for close-focus, so I wonder if the same may be true of your lens.