M3 rangefinder calibration (DIY)

rxmd said:
No offense meant, but most people ruin the first cameras they start working on - best start with a Zorki rather than an M3.



If you start working on this yourself, just remember:
* re/the shutter capping issue: Leicas are finicky with over-tensioning the shutter; you will probably need less than 1/4 or 1/3 turn of the tensioning screw.
* re/light seals: there are a number of places where light can creep in - through the back door, around the shutter curtain, from the top - so I'd check where it's coming from. This includes test shooting a roll of colour film to check whether the light is coming from the front or the back, you don't see that with B&W film. There are some seals that are tricky to replace, such as the ones in the slit where the curtain runs (you can't take just any material).
* re/adjusting the 10m and 1m points: it helps to have a known good lens and adapter and some way to check accurate focus on a ground glass with a strong loupe. You obviously need a target exactly 10m and 1m away (or an adjustment stand with the respective optics). For 1m you can shine a laser pointer through the back of the RF window and adjust until you get the points to align (of course for 10m you can do the same if your laser pointer is powerful enough and you have enough free space). And 75m is not far away enough for infinity focus, 5 miles would be OK, but the easiest is to use the moon or a star.
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Right my test roll says the rangefinder is fine and I'm fussing over nothing. Does anyone make a lens with decent/accurate distance markings, voigtlander and canon certainly can't IME?

Can you explain how a colour film (are we talking neg or slide here) can show where the light leak may be coming from, I'm not going to attack any inner light seals, my limits are the rear door and that is all I'm touching :)

funkydog said:
Even if you currently consider this M3 as your one and only forever camera, please - for the benefit of future users - either spend the money to fix it or sell to fund one in working condition.

In the past, I've bought a M2 and M4-2 off Ebay touted as "CLA'd". Turns out the self CLA involved crude adjustment of the rf roller. The screw threads were damaged by someone going in at an angle with a non specialized tool.
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I'm not a gorilla with a tool box, I'm not planning on doing anything beyond my abilities to make the camera any worse, I just cannot afford for Malcom Taylor or CRR Luton to work their magic at the moment.
 
Puggie said:
Can you explain how a colour film (are we talking neg or slide here) can show where the light leak may be coming from, I'm not going to attack any inner light seals, my limits are the rear door and that is all I'm touching :)
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It works only with negative film, which is nice because it's also the cheapest film.

Negative film has a coloured backing. If the light leak is in the front, the light will be normally coloured; if it's in the back, it will be tinted from the colour backing.
 
fantastic, so the roll of Velvia in there is no use whatsoever for checking this :)

I have a half exposed roll of Portra 400 and some Fuji 800 at home, I'll try with one of those next. is there any benefit with faster film?

Thanks for the info.
 
Puggie said:
I have a half exposed roll of Portra 400 and some Fuji 800 at home, I'll try with one of those next. is there any benefit with faster film?
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Not really. Maybe it gets marginally more visible with faster film. But there is a benefit with cheaper film :)
 
Cheers, I'll poke a roll of something cheap through and see if I can work out what it is, 'brief' chat with Malcom Taylor suggests it is a rear door or rangefinder leak, and I can't afford for him to service it for 3-6 months! But he does seem to know his onions so its maybe worth him doing it, CRR of Luton are 2/3 the price according to their website., is it 2/3 of the service? if Its rear door I'll probably just tape up between re-loading and not use the 1000th setting until I can get it sent away.
 
Where is the light hitting the neg? The shutter-gully light traps are also an usual suspect, It's like a smear at the edge of the frame, I'll see if I can find an example
 
... like this;

6263337518_ef26ed4f96_z.jpg


... I've never had any trouble with the door, it hasn't got any seals as far as I know
 
There are felt strips that are beside the shutter tapes, at the top and bottom of the shutter. You can't see these strips because they are behind the metal light shield in the film chamber. I'd be suspecting those, because of the location of the leak.

These strips are notorious for falling off and jamming the camera.

Oh, there is also a light seal at the top of the rear door flap. Check it for integrity.
 
I was getting occasional banding between the sprocket holes:

neg.JPG


ignore the yellow banding dodgy interference, the lightbox is using fluorescent tubes.

Just want to say very grateful of all the advice given to the noob in this thread :)
 
I came across the perfect tool for adjusting the infinity setting on the Ms (the large screw) -- in our kitchen drawer. The slot is rather large, and not accessible straight on. I found that a small spreader, for cheese or dips, is perfect -- it has a widish flat blade that is rounded at the tip, all the way around to the top of the blade. It engages the entire slot at an angle and works perfectly.

You can find these things at kitchen stores and gift shops.

Jockos said:

^ click for larger image.


She aint pretty, but works very well. It's a piece of 1mm thick aluminum, cut to a rough L shape. I found that it's easier to use if the holding part continues a little behind the "foot".
The "foot" end is filed to roughly one third the thickness, it's important that you don't file it to a sharp V-shaped edge, but rather like this: \_/, otherwise you may wear out the adjustment screw, and risk using to much pressure to keep the tool in the slit.
Be sure to not apply any excessive force upwards.

This can only be used for infinity adjustment, so unfortunately I don't think it will solve your problem :(
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