Rangefinder Calibration

Discussion in 'Beyond the Basics' started by stingray, Feb 11, 2006.

  1. stingray

    stingray TPF Noob!

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    Yesterday, after eyeing a camera or two in the window of a shop in a Melbourne alley that only open 3 hours and day and only on weekdays for a while, I finally made it in there and purchased a Voigtlander Vitoret R in fairly good condition, at least the shutter works well... However, after gazing through the viewer for a long while I tried to set the lens on a setting, 3.5 feet (for focus) and then measure said distance and see if it all lined up.. of course it didn;t.
    I am wondering if there is a way of methodically calibrating the "focusing" mirror so that it runs according to the markings on the lens.
    I assume though that the lens markings are very approximate and don't necessarily correspond to the distance exactly.
    I am willing to mess around with the camera as it didn't cost me a whole lot and I'm interested to learn the process myself and not shell out more money to have the thing fixed, thanks in advance,
    William.
     
  2. ThomThomsk

    ThomThomsk TPF Noob!

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    I don't think the distance markers on the lens are going to help you here. The first thing to check is that when you set the lens to infinity it really is focussing on infinity. The moon is a good subject for this test. If you can set the lens beyond the point where the moon is in focus, then the horizontal calibration is off.

    Here is something that I copied from a thread on the rangefinder forum. It was written by Stephen Gandy, who is the Voigtlander distributor for North America:

    Suggestions for checking the rangefinder on ANY Leica mount rangefinder

    1) Forget testing anything with a Russian screw mount lens. Your results vary with the Vodka ration the day the lens left the factory.

    2) Infinity for test purposes is something with straight at least a MILE away (or further). Infinity is NOT across the street or a few blocks away.

    3) IF the rangefinder aligns correctly at infinity, 99.9999% of the time the rangefinder will also be correct throughout the rest of the focusing range, so no other check is necessary unless you are having focusing problems at other distances.

    4) it is toughest for a camera's rangefinder (any rangefinder) to focus lenses accurately wide open and close up. If you are using a fast lens like a 50/1, 75/1.4, 85/2 or 85/1.5, or a 135 lens, make sure the camera's rangefinder effectively baselength is long enough to handle the lens consistently -- instead of claiming you are having rangefinder accuracy problems when in fact you are just asknig too much of a particular camera / lens combination.


    Let us know whether infinity is correct. If it is OK (or close enough), then I suggest you put a film through the camera, with test subjects at a range of distances and aperture settings, before getting in there with your screwdriver. I'd like to see some pictures too - I have a modern Voigtlander, and I'm always interested in anything taken with a rangefinder.

    Thomsk
     
  3. FuddyDuddy

    FuddyDuddy TPF Noob!

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    Hello,

    You are making your measurements to the film plane, not the front of the lens, aren't you?:er:

    There are 2 ways to check whether the camera is focusing properly:

    (a) Stick a roll of film in the camera, take lots of shots at a fairly wide aperture, have the film processed and see if things are sharp. This has 2 disadvantages: (1) a roll film of boring pictures you have to process - you have to pay for these things (2) the time taken to take the pics and wait for the film to come back.

    (b) With the shutter open, the lens wide open, and the camera on a tripod, place some Scotch tape over the hole in the back of the camera where the light hits the film. The tape is taking the place of the film and acting as a ground glass screen, so it needs to be in the same plane as the film would be.
    Focus on something through the viewfinder. Something with writing on it is ideal - say a cereal box on a table. Having focussed, take a look on the image projected on the Scotch tape (you may need to put a dark cloth over your head and the back of the camera to do this, and also a loupe or some other magnifier). If what you focussed on through the VF is sharp on the Scotch tape, then the camera is working fine, if it isn't then it needs attention. Repeat at different distances.
    Don't forget to remove the Scotch tape when you've finished!

    You can use tracing paper instead of Scotch tape if you're worried about gunging up the back of your camera.

    Regards

    Fuddy
     
  4. stingray

    stingray TPF Noob!

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    thankyou very much for the tips, i tried the moon and that seems to be all correct. I developed the first roll through the camera last night and it came out really nice. i'm happier with it than what i've taken with my EOS10, had been carrying it in my pocket at school all the time and got one of a crashed hot air balloon on our oval one morning.
    The focus seems to be absolutely fine and I even got most of the exposures right, quite an accomplishment for me seeing there's no meter.
    I'll post a couple up here soon, we're getting a neg scanner in tomorrow which will be fantastic... no more negotiating time in the school darkroom. Thanks a lot again, Will.
     
  5. stingray

    stingray TPF Noob!

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  6. ThomThomsk

    ThomThomsk TPF Noob!

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    Very nice stingray. T-max 100 looks like an amazing film, and there's obviously nothing wrong with your 40 year old camera. Well done.

    Thomsk
     

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