Rangefinder Recalibration

[paulsydaus]

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Hi all,

I have a very basic question about rangefinder recalibration. When a calibration is performed, can this only be "ideally" calibrated to one lens? What happens if you have multiple lenses? I suppose then you can then try to find a "median" calibration that minimises accumulated errors across your total kit, but it's not possible to get a perfect calibration on every one? So is it best to do the calibration on your widest or most often used lens?

I'm slightly confused about this issue.

Thanks everyone,

Paul

[250swb]

The calibration should be done to the factory specification on your body, not to match a particular lens. If the focusing is still out your lens then needs calibrating to factory standards. They should never ever be calibrated to force a body or lens to work together by artificially over/under adjusting one or the other. This would lead to the absurd situation where your lens can only be used with one body, or your body only used with one lens.

 

Steve

[paulsydaus]

The calibration should be done to the factory specification on your body, not to match a particular lens. If the focusing is still out your lens then needs calibrating to factory standards. They should never ever be calibrated to force a body or lens to work together by artificially over/under adjusting one or the other. This would lead to the absurd situation where your lens can only be used with one body, or your body only used with one lens.

 

Steve

 

Thanks Steve, I understand completely.

Out of curiosity, how do they change the calibration on the lens?

[StephenPatterson]

Since the early 1930s Leica have made camera bodies and lenses to a "standard", and in doing so greatly expanded the usability and flexibility of the system from the earlier practice of matching lenses with bodies with identical serial numbers. Thank you Steve for your excellent explanation of why this is so important.

[StephenPatterson]

Out of curiosity, how do they change the calibration on the lens?

 

Shims are used to adjust the spacing of the lens elements/groups

[jaapv]

Perfectly correct. However it is done -like any mechanical process- within (narrow) tolerances. With particularly critical lenses like the Noctlux or Summicron 90 it can sometimes be useful to have tolerance matching done, ie. compensating a negative tolerance with a positive one.

[paulsydaus]

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Perfectly correct. However it is done -like any mechanical process- within (narrow) tolerances. With particularly critical lenses like the Noctlux or Summicron 90 it can sometimes be useful to have tolerance matching done, ie. compensating a negative tolerance with a positive one.

 

Thanks,

Yes I didn't understand this issue but now I do so thanks.

Yes I am using Noctilux and the back focus is very large on two bodies. So I suppose it is the lens that's out of spec. It's quite new and I'm surprised that such a premium lens could leave the factory with such a large back-focus.

Paul

[thighslapper]

Thanks,

Yes I didn't understand this issue but now I do so thanks.

Yes I am using Noctilux and the back focus is very large on two bodies. So I suppose it is the lens that's out of spec. It's quite new and I'm surprised that such a premium lens could leave the factory with such a large back-focus.

Paul

 

I have not seen anyone complaining about a Noctilux out of spec on this forum in the last few years ...... 50/1.4 and 75/2 ... yes.....

 

I have rangefinder calibrated my bodies using the Noctilux and I would be surprised if it out ..... much more likely that the bodies are out and the critical nature of the Noctilux shows it up..... and are we talking about infinity, close up, or both ?

 

plus it depends what other lenses you have and whether they are ok though..... need more info to make firm diagnosis

[TonyField]

Rangefinder calibration on the Leica is rather interesting. For example, a complete rangefinder and lightmeter recalibration is done after a sensor replacement.

 

Here is an interesting video that shows how the M9 is put together and how the rangefinder is adjusted ...

 

[sblutter]

On those tough lenses all the way open I suggest shooting a 'focus bracket' if possible

 

Paid off yesterday with 75mm @ f:4.0

[paulholland27]

I've had my 35 Summicron ASPH for 14 years on a variety of bodies(M6,MP & M9) and have been very happy. Recently been lucky enough to get hold of a second hand 50 Summilux ASPH, which looks from the serial to be very recent(in the last year) but i am really having problems getting tack sharp images. In the UK is Leica the only place to get your M9 body or lens calibrated?

[TonyField]

Paul .. if you have problems with "tack sharp" images from your 50mm, you might run a test to see is this is focus shift when you stop down. With the camera on a tripod, shoot a good target on a detailed background (like a newspaper) from a distance of about 10 feet at 1.4, 2, 2.8 4, and 5.6 and make sure you have a good angle (about 30 to 45 degrees). You can see the effects of focus shift (which is normal for high speed lenses).

[paulholland27]

Thanks Tony, time to get a tripod i guess.

[TonyField]

Sorry Paul. I should provided this link. My 50mm F1 has expected focus shift when stopping down. If you examine the images I provided, you will see that the point of critical focus move away from my target as I stop down. You should see a similar (but probably not as large) effect with your 50mm F1.4.

 

http://www.l-camera-forum.com/leica-forum/leica-m-lenses/300946-50mm-f1-noctilux-focus-shift.html

[tobey bilek]

I have a book by one of the Leica employees at the time. The Summicron, Summilux, and 1.0 Noct were compared for distortion, coma, and center/corner sharpness.

 

The then current `Lux had the most distortion by far, almost no coma, and a bit of focus shift.

Must be why I could never find one to my liking, the focus shift. It was clearly designed for low light 1.4 performance. The were comparisons to Nikons 1.4 and well, there was no comparison.

 

The Noct was as sharp as the Summicron right into the corners if one adjusted for the focus shift. The Noct is indeed a universal 50 disregarding size and weight. The problem is if it were used for 5.6 pics, the focus need to be compensated manually and slowing things down .

 

I stuck with the Summicron series.