Accurate rangefinder focussing

[jwillyf]

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I have an M246 and yesterday was attempting focus on a fairly distant fence line with my Elmarit 90. I was unable to fully sync the two images in the rangefinder, with them coming close but not quite meeting, even at full rotation of the focussing ring.

Back home, I focussed on another distant object with the same lens at f8. Placing focus at infinity, this coincided with focus peaking in the LCD although the images did not coincide in the range finder.

Moving to a focussing chart at about 6 ft from the lens, I focussed using focus peaking at f2 to give minimum depth of field, I took a first shot. Through the rangefinder, the two images were not accurately overlapping. I turned the focus to bring them together and took another shot.

Under magnification the image taken using the range finder is definitely soft compared with using focus peaking.

I repeated the exercise with a 50 mm with a Summicron 50 mm f2 and a Voigtlander 35 mm f1.7. With the 50 mm lens the outcome was much the same. It was  much less obvious with the Voiglander ? because wider angle has greater depth of field. However with the two shorter lenses, it was more difficult to use focus peaking accurately since the peaking showed at a static level for some rotation of the focussing barrel.

My questions are:

1) Is the conclusion that the range finder focussing needs adjustment?

2) If rangefinder focussing is out, is focus peaking the technique to use preferentially?

3) If range finder calibration is out, is it possible for an amateur to adjust this camera, or does it need to be sent to an official repairer?

4) If an amateur can do it, is there illustrated guidance available on the web?

[stephan54]

Had this problem with a Summarit 90 2.5. My other lenses were focussing fine.

Leica tried to calibrate the lens, but were never successful. Not after three tries. I swapped it for a Telyt 135.

If your rangefinder needs adjusting depends on how your other lenses perform. Would not try that myself, but you might be handier than me.

Edited April 29, 2020 by stephan54

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[dkmoore]

3 hours ago, jwillyf said:

I have an M246 and yesterday was attempting focus on a fairly distant fence line with my Elmarit 90. I was unable to fully sync the two images in the rangefinder, with them coming close but not quite meeting, even at full rotation of the focussing ring.

Back home, I focussed on another distant object with the same lens at f8. Placing focus at infinity, this coincided with focus peaking in the LCD although the images did not coincide in the range finder.

Moving to a focussing chart at about 6 ft from the lens, I focussed using focus peaking at f2 to give minimum depth of field, I took a first shot. Through the rangefinder, the two images were not accurately overlapping. I turned the focus to bring them together and took another shot.

Under magnification the image taken using the range finder is definitely soft compared with using focus peaking.

I repeated the exercise with a 50 mm with a Summicron 50 mm f2 and a Voigtlander 35 mm f1.7. With the 50 mm lens the outcome was much the same. It was  much less obvious with the Voiglander ? because wider angle has greater depth of field. However with the two shorter lenses, it was more difficult to use focus peaking accurately since the peaking showed at a static level for some rotation of the focussing barrel.

My questions are:

1) Is the conclusion that the range finder focussing needs adjustment?

2) If rangefinder focussing is out, is focus peaking the technique to use preferentially?

3) If range finder calibration is out, is it possible for an amateur to adjust this camera, or does it need to be sent to an official repairer?

4) If an amateur can do it, is there illustrated guidance available on the web?

1) most likely needs adjustment (if you used a tripod for your testing)

2) Yes until fixed

3) Yes, but I wouldn't try it as I am not all that handy

4) search this forum and there are diagrams for this adjustment. Unfortunately I haven't seen any video how too.

I would use live view until Leica opens up again and then send it to them to adjust. Or, send to DAG  who is fantastic and QUICK. He is also very well priced.

Good luck!

[jwillyf]

Thanks foe the replies. Sorry, but who is DAG. I live in the UK

[bags27]

7 minutes ago, jwillyf said:

Thanks foe the replies. Sorry, but who is DAG. I live in the UK

Madison, Wisconsin.

[peterm1_Leica]

The way I have handled this has been to set up a target at a measured distance. I used 3 metres simply because it was also marked on my lens.

The target was a 1 metre long length of wood, which I laid flat on the floor with the focus point marked in the middle and with 2 centimetre intervals also marked forward and backwards from that point so it would be easy to see how much if any focus is off. I set the camera up on a tripod such that the cameras focus plane (i.e. its sensor - not the end of the lens) was exactly a measured 3 metres from the central focus point as marked above. Then take an image focused by rangefinder on the central focus point plus a further image "focused" based on the lens's distance scale (i.e. with the lens set at 3 metres). If both coincide the lens should be OK. If the distance scale method results in a fuzzy image of the focus point this tells you that the lens calibration must be off from where they should be. If the rangefinder is off too, this will tend to confirm this. You will readily see whether the focus point falls in front or behind and by how much. Repeat the experiment using focus peaking. This time focus on the central focusing point as accurately as possible using FP and then check the lens's distance scale to see how it reads. If the distance scale corresponds to 3 metres then this would confirm that the problem is not the lens calibration but the rangefinder's and it is the rangefinder that needs re-calibration.

My first thought is that this may not be the rangefinder but the lens. My reason for thinking this may be so, is that  you were having issues with infinity focus,  (if I read you correctly). To check this, find a very, very far target (i.e. one that is effectively infinite - a tree or tower on the horizon or near it) and see if using the rangefinder the camera will allow you to focus the lens at that extreme distance. It sounds to me from your description that you may have already done this and it could not - you said that even at full rotation the rangefinder images could not coincide. 

This rather strongly suggests to me  the possibility that the lens is front focusing somewhat significantly preventing it from reaching infinity.  As I said,  from your description I would strongly suspect lens calibration is the issue rather than the camera rangefinder. 

I have had this problem before with an old Canon 50mm f1.2 I bought. It worked OK on a micro four thirds camera using focus peaking -  tother than that it could not reach infinity - much as you described with your Elmarit, but would not focus accurately at all on my M8 using rangefinder.  In my case I found out that the internal adjustment "shim" ( a thin dohnut shaped brass ring) was marginally too thick, putting all the lens elements further out than they should be thereby screwing with focus accuracy at all distances when using the rangefinder. (I have NO idea how this happened as the shim is factory installed and this would suggest that the lens's calibration must have been off ever since it left Canon's factory 60 years ago. Or possibly someone, a previous owner of a sloppy technician swapped it out for some reason...who knows.)

Another even more common way this may have occurred is that someone may have disassembled your lens for lubrication purposes, then reassembled the helicoid assembly wrongly so the helicoids do not register with each other correctly. This results in the lens either front focusing or back focusing, depending on the direction of the error. If so, it is conceptually easy to fix in theory, but it is what we in Australia would describe as a "fair bugger" to fix in practice, as once it has been reassembled incorrectly, it usually then requires trial and error to  get it right - the problem is that there are lots of ways to wrongly reassemble a helicoid so that its registration is off, and only one correct way. But a technician can do it. (Even I have done it which is why I know it is a "fair bugger" :^)  )

How long have you had the Elmarit 90mm? Do you know anything of its history? Specifically do you know if it has been taken apart?

Edited April 30, 2020 by peterm1_Leica

[jwillyf]

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Thanks, peterm1_Leica, for your detailed reply. I will try out your suggestions when I have a moment, and feedback.

I have had the Elmarit 90 for about 18 months, bought on Ebay, and I know nothing of its history

[davidmknoble]

I have a chrome version of the elmarit 90 and have not had trouble.  I would suggest that if your other lenses work well, that the rangefinder is probably well calibrated.  That leaves the lens and the cutout on the back of the lens is what drivers the rangefinder mechanism.  So, the lens may need another mount or the mount adjusted.  Just a basic thought...

[jwillyf]

  I have taken some further shots with all three lenses, this time first focussing with Live View peak focussing, and then checking out how much, if any, focus movement was required to focus using the rangefinder. With all three lenses there was a discrepancy between Focus peaking and range finder  with the Peak Focussing giving sharper images than the rangefinder.

I guess this means the camera rangefinder needs re-calibrating?

[jwillyf]

The 246 goes off to a UK repairer tomorrow. I will feed back.

Thanks

[jwillyf]

Just reporting back that my 246 is now back from Alan Starkie of cameraworks-uk.com here in the UK, having had the rangefinder calibrated.

A result, with infinity focussing now correct, and concurring rangefinder and Live view focus peaking, with crisp images. A great service from Alan.