Hexing the Wild Rangefinder

[lars_bergquist]

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A couple of weeks ago, I sent my 90mm Elmarit-M to Will van Manen for focus adjustment and coding. The lens returned, coded and with test pictures to show that focus was tack sharp -- but the lens did still backfocus about 5cm at 2m. Had mijnheer van Manen made a mistake? Had I made a mistake? No -- it was the Gnomes of Solms. Read my email reply to van Manen:

 

Från: lbq@telia.com

Ämne: Follow-up report

Datum: tisdag 30 nov 2010 11.06.51 GMT+01:00

Till: Third party email address removed

 

Dear Mr. van Manen,

 

This is about the 90mm Elmarit-M you handled recently (and which cost me extra on its way back home – remember?)

 

My dear deceased father-in-law used to say that everything of interest in newspapers had to be read between the lines. He should know; he was a hand typesetter at a major Stockholm morning paper. I think letters too should be read between the lines. And betwen the lines of that nice letter that accompanied the Elmarit home, I read: "There is really nothing wrong with the focusing." A quick test of the lens confirmed that focusing had not changed. It was still rear-focusing on my M9.

 

Now this was difficult for me to swallow, for earlier this year, the M9 cracked its sensor filter, and had to be returned to Solms for a sensor change. It was strange to my mind that the camera should have left Solms with a new sensor and the rangefinder – or the sensor – out of whack. I did nevertheless take a 2mm insex wrench and a deep breath and started to adjust the rangefinder for best focus at 2–3 meters with the Elmarit. Slightly to my own surprise, I managed to get a good focus.

 

Now I had to check the other lenses. The 35mm Summilux ASPH v.2 was OK, of course – I did not bother to check my real wide angle lenses! The 50mm Summilux ASPH was still giving acceptable focus, though with a very slight tendency to front-focus. And, wonder of wonders, so did the Apo-Telyt!

 

All these results are preliminary, of course. I will have to work with the camera and lenses in real life to be completely convinced. The crux is the 90mm lens, because I am really a "35 plus 90mm man". Maybe that has to do with my being at the impressionable age of 22 when the M2 was introduced.

 

But – the newly adjusted rangefinder does not give perfect coincidence on the church spire at 2km I use for infinity testing. It is not as bad as a full double image, but the helicals of all my lenses now go a hair past infinity! This does not trouble me overmuch – spires at 2km is not my normal subject matter. But it reinforces my suspicion that Leica did goof.

 

So thank you very much Mr. van Manen for telling me in such a diplomatic manner that somebody was wrong. I am relieved to find that I was not alone in this; the Gnomes of Solms were wrong too.

 

Sincere regards, Lars Bergquist

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[wattsy]

Jesus wept! Expecting to learn something interesting, I just wasted a minute or so of my life reading that.

[lars_bergquist]

What I learned was that a M9 can leave the Solms repair department with the lens flange–to sensor distance out of tolerances. Such things can happen. Don't tell me that is trivial.

 

I had missed this first because the camera returned from Solms in August, and since then I had used it mainly with wide and superwide lenses. It was when I failed to get correct focus with my Elmarit – which had previously been to Solms to correct its focus and returned tack sharp – that I decide to see what Mr van Manen could do with it alone, i.e. without the camera. Sending both camera and lens to Solms would have meant that I would have been M9-less over the Christmas holiday.

 

The fact that all my lenses now focus very well thank you, while the rangefinder is off at infinity, tells me that my camera's critical Anschlagmaß is off. I am happy that I can move that error away to a place (infinity) where it does not bother me, instead of sending the camera back to Solms to have the bayonet shimmed or whatever, is also a great relief.

 

Also, the fact that Will van Manen did a good job and was diplomatic to his confused customer, is not unimportant either. At least to him and me.

 

The senile old man from the Age of Trivial Pursuits

[archi4]

Lars,

My M9 was off straight out of the box - Because all my lenses and my M8 bodies had been calibrated in Solms to "Leica standard" and focused perfectly I checked infinity with a far tower and the moon and discovered that the rangefinder never reached coincidence. I adjusted as you did but checking coincidence of moon and tower and not focus and now all my wider lenses are exact at all distances. (summilux 50ASPH, 90 elmarit, s'cron 50)

I only adjusted the wheel. If it had been necessary to change the arm, I would have called Solms.

regards,maurice

[lars_bergquist]

Well Maurice, ya wus lucky! The rangefinder of my M9 coincided perfectly on that church spire at two kilometers, but the Elmarit was off. Now after adjustment the Elmarit is on, with the rest of my lenses – and the rangefinder is off at infinity! Meaning this was not a rangefinder error; it was and is a sensor adjustment error.

 

Pious pixel peeping has not made obvious any difference in definition however between pictures at that distance taken at the end of the helical – "mechanical infinity" if you will – and pictures with rangefinder coincidence (which occurs about 1mm earlier). That is not terribly difficult to understand. First, the rangefinder cannot really discern small differences at distances beyond about 200 meters; second, haze and mirage and the basic optical properties of even clean and still air do perceptibly decrease definition at long ranges. And third, depth of field is considerable at that distance even at 2.8.

 

So this slight fuzziness of the distant spire in the rangefinder does not disturb me, as long as my lenses focus accurately at practical shooting distances. And now they do. Sens moral: Caveat emptor.

 

The old man with the Allen wrench

[jaapv]

Not necceseraly a flange distance problem, in fact rather unlikely. The RF arm needs adjusting, at least at two points. Call our friend Will

[barcoder]

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Lars,

 

I loved your letter. It was well written. If only all my emails had that much thought.

 

Lee

[lars_bergquist]

I have been in contact with Will van Manen and Ms. Kuiper, and they suffest that Jaap Vleeskruijer is right: The finder arm neds adjustment. The roller adjustment of course is just one of several ("several" = more than two) RF adjustments, even horizontally. He mentions that the Leica Manual uses five pages to explain this work, which I prefer to leave to those qualified for it.

 

One interesting point in his mail to me this morning is the following: "We never adjust equipment to each other. So, we adjust your camera with our test/adjustment equipment to a (almost) zero tolerance. We do the same with your lenses on our test body, also to the same 'zero tolerance'. This way, each combination will be in tolerance."

 

So, when I emerge frome the Yule coma, off goes my M9. Then we shall see what other lenses, excepting the already-adjusted 90mm Elmarit-M, that need adjustment.

 

I must say that the more I learn about Will van Manen, the more confidence I have in him – one craftsman to another! Even though my craft was typography.

 

The old man with the screwdrivers

[Nicoleica]

I must say that the more I learn about Will van Manen, the more confidence I have in him – one craftsman to another! Even though my craft was typography.

 

Lars, I cannot agree more. Both Will and Cathy are true professionals, and very nice people too. Every camera and lens that they have serviced and/or repaired for me has been returned fully meeting, or even exceeding, my expectations. These days I try to deliver my items to them in person, as I always prefer personal contact if possible. (Also, it sometimes helps to be able to explain or demonstrate an obscure problem or request, rather than try to do this solely in writing.)

[ho_co]

This thread should be required reading for all Leica M owners.

 

Yes, one can easily and quickly adjust the rangefinder cam follower in the camera, and doing so will often correct the obvious problem.

 

But in all cases of such emergency adjustment in the field, Leica recommends sending the camera to a competent repair technician for full adjustment as soon as practicable afterward.

 

The rangefinder mechanism would not have survived virtually unchanged from the days of the M3 if it weren't up to the task of exact focus (sometimes with the need of additional finder magnification) with Leica lenses.

 

 

Note: This is a side issue to the question of quality control of both lens and rangefinder adjustment at the production stage.