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  1. #1
    Dr Croubie's Avatar
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    Calibrating R3A, camera or lens or both?

    So I've recently bought a Bessa R3A off fleabay, and a Canon 135/3.5 from a classified here. Put my first roll through it, TMax400, dev'd myself in Xtol 1+1 for 10 mins or so. Results came out great (metering-wise), except that almost every shot was front focussed.
    Have an example:
    Click image for larger version. 

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    The focus was on the dog when I took the shot, but on the neg it's focussed on the car (which should have been in the shot, still getting the hang of framing with an external VF), or maybe even a bit closer than that.
    I've read "the" instructions for calibrating the rangefinder, and I'm unsure which way I should be going about it.

    Firstly, infinity is fine. On the only-two rangefinder-coupled lenses I've got (135/3.5 Canon and 21/4 Skopar), rotating the lens until it hard-stops at infinity, the RF patch is perfectly in focus on the farthest tall tree I could find.
    Vertical is also fine, that's easy to notice even without a lens if it's off.
    The patch itself is sharp and in focus.

    So where's the problem? Do I need to adjust the close-focus screw? (mentioned in the link but not exactly explained)
    Or could there be another problem, like the RF cam is telling me i'm focussed at 3m when in fact the position of the glass elements are focussed at 2m?
    To test the latter, I've had the idea before of using an SLR focussing screen, held over the film-area, with the back open and the shutter locked open on B, to see if what the RF tells me in focus agrees with on what the lens is focussing.
    Despite the logistical nightmare of using all my fingers at once holding various things, dirtying the focussing screen, and the risk of the shutter closing on the focussing screen and snapping both, it just doesn't tell me much because the DOF shown on the focussing screen just masks out any focussing errors.
    Besides that, it's hard to test the camera with my 'known good' 21/4 skopar, at 21mm f/4 everything's in focus, it's the 135/3.5 combo that neither are 'known' good.

    So without getting a digital Leica M (240) with live-view so I can calibrate the lens, or buying another brand-new lens (ie so it's 'known good', at least I'd hope they come good from the factory), am I just SOL without sending everything to get a CLA together? (which is probably going to cost me more than what the lens/body cost me to begin with).
    Any other tips or tricks that might help me out?
    An awful lot of electrons were terribly inconvenienced in the making of this post.

  2. #2

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    I believe the rangefinder baseline of the Bessa cameras is simply too narrow to be able to accurately focus a 135mm lens. And that probably is where your answer is.

    The rangefinder baseline -- the distance between the two windows -- is 37mm. With the 0.7x viewfinder, the effective base becomes 25.9mm. With the Zeiss Ikon, the actual base is 75mm (twice that of the Bessa) and the effective is 55.9mm (more than twice that of the Bessa).

    A wider rangefinder baseline allows for more accurate focusing, which becomes more important as you use longer lenses. I think the longest Cosina Voigtlander lens for the Bessa was 75mm. The 135mm is considerably longer than that, and you've probably exceeded the margin of accuracy of the camera's rangefinder.

  3. #3
    Newt_on_Swings's Avatar
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    Elekem might be right. A safer way to check without having to hold the focusing screen is to carefully stick a piece of scotch tape across where the film usually lies. Just dont get it on the blades. With a dark cloth draped over the camera you should see the image formed easily when shooting in bulb with a locking shutter release cable.

  4. #4

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    I concur with the replies so far. I wouldn't use a rangefinder camera with a lens longer than 90mm. To expect pin sharp results with a 135mm lens is probably asking to much of the rangefinder system. It's the reason why yesterday's professionals would often use a Leica with lenses of 35mm or wider, but anything for longer, then Nikon or Canon SLR's were brought into play.

  5. #5

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    Check the lens first, It's not uncommon for a lens to front focus. Sometimes it a characteristic of the lens and working aperture.
    Tripod, shutter on bulb, frosted tape or ground glass at the film rails not the guides.. With the lens focused on the GG then check the distance scale.
    The hard stop in the barrel doesn't mean the lens is actually focused properly and once infinity is found, the focusing ring or barrel can be adjusted to agree with the image.
    Using something like a 5X magnifier can give a more accurate image too.
    Heavily sedated for your protection.

  6. #6

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    The R3A is a 1.0x viewfinder, not 0.7x, works fine with a 135mm, I use it successfully all the time.

    Have you checked the front element of the 135mm to make sure it is screwed down tightly?

  7. #7

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    You are correct about the R3A viewfinder magnification.Even at 37mm, that is still a narrow rangefinder base, and I think it might be too much to ask this camera to accurately focus a 135mm lens. However, it is important to check infinity focus on the lens and that the camera's rangefinder is spot on.

  8. #8

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    Hello,
    I'm not sure whether the Canon lenses were fully compatible with the register and the slope of the focussing curve of Leica, Konica Hexar RF and Bessa rangefinders. Concerning the exact register there were slight differences between Konica and Leica, maybe also between Canon and Bessa.



 

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