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Thread: tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

  1. #1

    tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

    Well, the little unit arrived in the mail from Japan yesterday. It's quite an amazing little piece of engineering. And for something 3 decades old (am I correct on this?), it's in remarkably good shape. Two out of the three bubble levels still have bubbles in them. The third would be nice, but it's just as easy to pop a multi-level into the cold shoes.

    But when I check the relative orientation of the two format frames (with a vernier caliper) when they're sitting in the detent slots, I find that the tilt is out by about 0.5 mm, and the swing is out by about 1 mm. Is there any way to adjust the detents on these things?

    Thanks in advance.

    Evan

  2. #2

    Re: tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

    No.

    Unless you send it to Arca or an Arca repair service in the US (or wherever you live).

    If the frame - which one, front or back? - is off, it means that it had been treated very bad and bent by someone. Or it could be that you that the connection between the gear block and the standard is a bit loose. If you have the tools and a very good mechanical knowledge you could take the blocks and standards apart and check the screws. If not it would be better to hand it over to a camera mechanic.

    Where did you measure? Top, left, right, bottom?

    My 6x9 from 1984 features a deviation of 0.2mm of tilt at the front standard. The rest is just fine.

    BTW, you should e-mail Arca to send you new levels. You can 'glue' them with silicone from the DIY market. Just make sure the rail and the standards are level - check it with a large level of ~ 1 meter length.

    Is it the model like this one?

  3. #3

    Re: tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

    Hmm. When I measure it one way (between the format frames at the tops versus the bottoms), there's an issue. But when I measure as per the attached photo (ie, with a dimensionally stable carpenter's level laid across the rail, holding up a 90 degree square), I can't find anything out of alignment. So I'm thinking that maybe I should just leave well-enough alone. Can I assume that if I shoot mainly with the smaller apertures, then likely most of the image will be in decent focus anyways?

    Thanks TD for the info. I suspect that mine is an earlier model than yours. Hopefully the photo reveals enough. I'm thinking that I have a pre-1984 model (?).Click image for larger version. 

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  4. #4
    ic-racer's Avatar
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    Re: tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

    The center detents need to be set with much precision on a medium format view camera. Think of how upset one would be if a Hasselblad lens were off center by just a fraction of a millimeter.

  5. #5

    Re: tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

    Your Arca is the predecessor.

    It's not an easy task to check levels. Today with everything made in China you can't even rely on a long spirit level from a DIY market anymore, unless it is a brand name with a certificate.

    Start with a levelled rail by placing your camera with the rail onto a levelled granite kitchen top or by levelling the rail on a geared tripod head. Level the horizontal from front to back and left to right. Then check the verticals by placing your triangle onto the granite plate and against the standards on the right and left side, then to the front and back of the standard. Remove the bellows and one standard to check one single standard. Keep in mind that all parts are precision milled, the rail can not be bent. If the first standard is ok, check the second one. Then mount both standards, pull them apart as much as the rail allows. Move the standards (frames) up and place a long spirit level diagonally across the lower beams of the standard (frame base). That means from the right hand side of the base of the rear standard to the left hand side of the front standard. Then change sides. If there is a tiny deviation, don't worry. Your camera is in a top condition.

    After you have checked the levels, check your bubble levels and place a small mark with a thin waterproof felt tip pen in the middle of the bubble levels. Even if they should be off, with your marks they will be spot on. Don't rely on the cold shoe level - these cheapos feature a large deviation, and the cold shoe is not as precise as the camera (because it does not have an optical function).

    Next check: Mount the ground glass to the back, use a lens plate without a lens, tighten the standards on the rail and measure the distance from the front side of the lens plate to the ground glass with a calliper. Now insert a roll film back without film, remove the dark slide and measure again. As long as the difference is in the range of 1/10 of a millimeter (film thickness added), everything is ok.

    Keep in mind that the Arca is completely different to a Hasselblad. You are using large format lenses, starting at f=5.6, featuring a large image circle. If the above measurement is ok, there is nothing to worry about: You will get a sharp image on film as long as you focus it sharp on the ground glass. You have a moveable flange, a Hasselblad doesn't. So for a HB it's vital that the flange distance corresponds to the specs, because the lens and not the flange distance is used to focus.

    Far more important is the correct distance to the ground glass. Some people mount a new gg 'sunny side up', that means the matte side pointing to the photographer, which means they are off in focus my 1 or 1.5 millimeter. This is a real disaster. A tiny bit of tilt, shift, rise or fall wouldn't be noticeable at all unless you would photograph grid lines, Siemens stars or USAF resolution test charts.

    Calibrating your camera and the levels with this procedure is the best you can do. A single bubble level in a camera can have a deviation of up to 0.5 degrees. But if you have marked your levels as above, the measuring base is considerably longer and almost 100% to the spot.

    For more information about precision spirit and bubble levels check my blog and visit the web site of the company. It is a real eye opener regarding the cheap hot shoe bubble levels.

    Now put a film into your roll film back, grab your tripod, go out and enjoy your camera...

  6. #6
    ic-racer's Avatar
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    Re: tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

    Quote Originally Posted by toyotadesigner View Post
    Keep in mind that the Arca is completely different to a Hasselblad. You are using large format lenses, starting at f=5.6, featuring a large image circle..
    Image coverage has has no effect on lens centering. Physics of lens centering perpendicular to the film are IDENTICAL to Hasselblad or any other medium format camera. I did not mention focusing accuracy or flange focal length.

  7. #7

    Re: tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

    Physics of lens centering perpendicular to the film are IDENTICAL to Hasselblad or any other medium format camera. I did not mention focusing accuracy or flange focal length.
    I know. But according to your statement it wouldn't be possible to shift, tilt, rise or fall any lens at all. Which is - as we all know - nonsense.

    Flange - lens distance: Must be perfekt with a standard lens for a medium format or 35mm camera, because the lens is calculated so that the lens elements move.
    For LF cameras or view cameras the focusing means moving the hole lens, not just parts of it. Thus the flange - lens distance will be modified.

    See what I mean?

  8. #8

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    Re: tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

    Check for cracks in the plastic front & rear standard frames. It is possible a crack is causing this problem. Check the rise adjustment screw area and other higher stressed areas of these plastic frames as they are known to crack. If a crack(s) are found, they must be properly addressed before proceeding to check for camera alignment accuracy.

    Various bubble levels can be purchased from Geier & Bluhm. Bubble levels are offered in various sizes and specified accuracy in degrees per unit length.
    http://www.geier-bluhm.com

    Camera store levels are of unknown specified accuracy and quality.

    Parallel alignment of the front to rear standard ground glass is important. It should be measured with the bellows removed and using a precision depth gauge capable of resolving 0.001". Move the two standards close together with the ground glass on the rear standard textured side towards the lens and reference detents set. Lock the movement adjusters. Then apply the depth gauge at the four corners of the lens board seating and ground glass. Using a triangle and construction level will not be accurate enough. Accuracy and precision here matters as when larger lens apertures are use, the alignment is critical. This requirement grows in tolerance as smaller apertures are used due to the increase in lens depth of focus. If there are camera alignment problems, they often result in out of focus areas in the film image no different than any other medium roll film format camera.

    The detents can be an issue when camera movement is used in small increments as the detents will fight the application of smaller units of camera movements. To compensate for this, the levels must be accurately calibrated, then detents de-activated. This allows fine adjustments of camera movements but relies in level accuracy.


    Bernice

  9. #9

    Re: tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

    Quote Originally Posted by toyotadesigner View Post
    Your Arca is the predecessor.


    Start with a levelled rail by placing your camera with the rail onto a levelled granite kitchen top or by levelling the rail on a geared tripod head. Level the horizontal from front to back and left to right. Then check the verticals by placing your triangle onto the granite plate and against the standards on the right and left side, then to the front and back of the standard. Remove the bellows and one standard to check one single standard. Keep in mind that all parts are precision milled, the rail can not be bent. If the first standard is ok, check the second one. Then mount both standards, pull them apart as much as the rail allows. Move the standards (frames) up and place a long spirit level diagonally across the lower beams of the standard (frame base). That means from the right hand side of the base of the rear standard to the left hand side of the front standard. Then change sides. If there is a tiny deviation, don't worry. Your camera is in a top condition.

    After you have checked the levels, check your bubble levels and place a small mark with a thin waterproof felt tip pen in the middle of the bubble levels. Even if they should be off, with your marks they will be spot on. Don't rely on the cold shoe level - these cheapos feature a large deviation, and the cold shoe is not as precise as the camera (because it does not have an optical function).

    Next check: Mount the ground glass to the back, use a lens plate without a lens, tighten the standards on the rail and measure the distance from the front side of the lens plate to the ground glass with a calliper. Now insert a roll film back without film, remove the dark slide and measure again. As long as the difference is in the range of 1/10 of a millimeter (film thickness added), everything is ok.
    Thanks TD. I'm not sure why I didn't think to simply find a level surface like a counter top to put the triangle on. But now I have, and things still seem quite squarish. And I think what I'll do regarding the bubble levels (and what I've done with my Mamiya 645 with a shift lens) is to put the rail on a known level spot, fix a couple of the hot shoe bubble levels to the frames and mark the bubble level with a felt pen (as you advised) or a tiny scratch in the plastic.

    And once I get a roll film back (I ordered a Horseman 6x7 today), I'll try the caliper trick with ground glass versus roll film holder.

  10. #10

    Re: tilt swing detent adjustment on Arca Swiss F-line classic 6x9?

    Quote Originally Posted by Bernice Loui View Post

    Parallel alignment of the front to rear standard ground glass is important. It should be measured with the bellows removed and using a precision depth gauge capable of resolving 0.001". Move the two standards close together with the ground glass on the rear standard textured side towards the lens and reference detents set. Lock the movement adjusters. Then apply the depth gauge at the four corners of the lens board seating and ground glass. Using a triangle and construction level will not be accurate enough. Accuracy and precision here matters as when larger lens apertures are use, the alignment is critical. This requirement grows in tolerance as smaller apertures are used due to the increase in lens depth of focus. If there are camera alignment problems, they often result in out of focus areas in the film image no different than any other medium roll film format camera.

    Bernice
    Thanks Bernice.

    I'll have to order a depth gauge (not only for this, but also for miscellaneous tasks in the garage). In the meantime, I've done something similar with a piece of straw from a broom and a slight mark with a felt pen. Just by eyeballing things, it looks like the front standard is parallel to the ground glass at least to the level of approx. 0.2mm to 0.4mm. If the depth gauge confirms something like this, is there something that I could shim? I initially thought of shimming the ground glass, but then I'd also have to shim the roll film holder, I would think. And any sort of shimming might increase the possibility of light leaks, I would also think.

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