Calibrating range finder in Mamiya Press Universal

Discussion in 'Medium Format' started by richard_hasty, Feb 6, 2002.

  1. I just bought a Mamiya Press Universal, and I'm quite happy with it
    except that the range finder is off. I took some pictures of meter
    sticks at 45 deg to the film plane to figure out what's wrong. It
    looks like the distance markings on the lens are OK, but the range
    finder doesn't agree with them. The range finder indicates a
    distance of 1.7m when it should be indicating 2m.

    Would this be a simple thing to adjust, or should I send it out to
    somebody? Can you reccomend somebody who works on these cameras?
     
  2. It's really not too tough (The description looks long, but it's simple in actual practice), although getting (and keeping!) several lenses all synced to the same camera can be challenging. The ideal way to do it is with a ground glass back, but comparing a tape measure to the distance markings will be sufficient unless you're planning to shoot a 100/2.8 or 250/5 wide open. Remember, the lens markings are from the film plane, not the end of the lens.

    (Note to others: these instructions work for the bright-frame finders on the Universal and the Super 23. They do not work for the Standard 23 or Deluxe, which have a totally different top end. The basic procedure is the same for the old bodies, but there are four screws, not two, and they're located somewhere else entirely. I only use my Standard to scale-focus my 50, so I've never bothered to adjust the rangefinder)

    First, be wary of adhesives on all adjustment screws. Many heavy users wanted to avoid things vibrating out of adjustment. The bright ones used nail polish (which I'd recommend to you also), which does the job, but breaks right off when turned with a screwdriver. The jerk who previously owned my 100/2.8, however, used very permanent epoxy. If the screw won't turn, investigate why before you ruin it, they're expensive to have remade :(

    If you have multiple lenses you have to pick one lens to adjust the body to, then adjust the other lenses to match the body. I believe neither the 90/3.5 or 100/3.5 have provision for lens adjustment; they're the ones to start with if you have one of them. The 50 and the 65 are a pain to adjust - you have to add or subtract shims - but generally are sufficiently slow and wide that they don't need to be dead on. The 100/2.8, 127/4.7, 150/5.6 and 250/5 have an adjusting screw inside the lens mount; sometimes there's a hole in the "mask" plate at the back of the lens to give you access, sometimes you have to take the mask off - just remove the obvious screws and set it aside.

    First remove the rangefinder cover - one screw on each side, plus you remove the knob which selects the 100, 150 or 250 bright frame. The cover then slides straight up. While you have the cover off, resist the temptation to clean any mirrored surface with anything wet - they're very easy to de-silver. A dry Q-tip used VERY lightly could be used to take off egregious dust, but don't sue me if you screw up.

    Towards the rear of the assembly, somewhat left of center, you'll see a screw at a 45-degree angle; that's your close focus adjuster. To the left of it is a similar screw that goes straight in; that's the main focus adjuster.

    To adjust the main focus, either find an object at infinity (like, a half mile away) or at the last marked distance on the lens. Focus on it with the ground glass if you have it, otherwise measure the distance. Note where this is on the focusing scale - use the DOF scale to help you if need - i.e. you can write down "the 1 of the 10m mark at left f/11" if that gives you the most precise description - then focus with the range finder (You may need to shield the mechanism with your other hand to keep out stray light). Note where it focuses the same way. Turn the main focusing screw about an eighth turn. I always forget which way is which, you'll find out in your first two tries :) Now go back to the range finder. Take it clearly out of focus and then bring it back into focus. Note where you are on the focusing scale again - are you getting better or worse? By how much? Keep going until the rangefinder focus as read off the lens is exactly the same as the ground glass or tape measure reading. (If you have any tendency towards dyslexia you'll probably need to stop halfway through for an aspirin or a scotch.) At the end you'll be making adjustments to the screw that barely qualify as nudges. Now repeat this procudure using an object at a close focusing distance. I use the next-to-the-closest-possible distance on the lens, but that's not gospel. Anything under 10 feet should be fine. Remember to use the angled close focus adjusting screw, not the main adjusting screw.

    Put the cover back on - you're done with the body! If you have additional lenses use the same procedure on them, but using the adjuster on the lens, and only at one distance, I use 12-15 feet, but it really shouldn't matter. If you have the 250/5 or 100/2.8 you may want to sync them to the body at 20+ feet, then use them to reset close focus on the body - their shorter DOF makes them need more precision at close distances. Also, for these two you really want to use a ground glass, not a tape measure. I know, the 2.8 is only 1/2 stop faster than the 3.5's, but it's actually usable wide open, the 3.5's really aren't. Don't set close focus on the 250 using a distance closer than about 13 feet - closer than that its rangefinder tracking is very different than the other lenses. You just have to live with the fact that this lens can't really be focused with the rangefinder closer than 12-13 feet.
     
  3. These directions were great, but I have an additional question. I have the 100 mm f3.5 lens, so that is what I refer to below.

    The question is regarding how well the range finder can be calibrated over the entire range. The "far focus" screw described above sets the point at which the range finder stops moving. If I set the far focus at 10 meters, anything farther than 10 meters away can't be lined up in the rangefinder. If I set it at 5 meters I can't line up anything farther than 5 meters away in the range finder... and so on.

    The "close focus" described above adjusts the coupling between the range finder and the lens in the way one would expect. The problem is that the range finder doesn't have the same "slope" as the lens. If I make 1.2 meters line up ( the second marked distance), then 5 meters is pretty far out of whack.

    Is this normal operation for this camera? Is there some magic combination of settings that will do better than this? Have I missed something obvious?

    I ended up using the "close focus" adjuster to set 5 m to be accurate, because that's about the distance I think I will want to use most.
     
  4. Sorry for not having seen your second question last year--Using other distances to set the
    far focus shouldn't cause that much of a problem--as long as you've got a focus match
    between the rangefinder and ground glass you should be O.K., although if you use a
    shorter distance I'd recheck the long focus after setting the short focus. If you continue to
    have a problem, yeah, revert to setting the long focus on something that really is at
    infinity.

    Note that there is apparently another set of adjusters buried deep within the rangefinder
    that set the actual cam tracking; they're factory set and adhesive locked. If these were off
    from the factory or have been messed with by a previous owner there could be a problem
    not resolvable through the "normal" adjustment procedure, but this seems fairly unilkely.
     

Share This Page