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Thread: Axis tilts and Ebony with off-centered panel

  1. #1

    Axis tilts and Ebony with off-centered panel

    Hello,

    Just playing with my new ebony 45s and getting used to focussing with axis symmetrical tilt for the first time, my previous camera had base tilts only.

    I noticed that my Wista lens board has an off-centered hole so the lens does not tilt right on axis. I'm finding that the area just below center of the frame is maintaining focus during the tilt and not the center of the frame as I had understood would be the case with axis tilts. I guess this is due to the off center hole on the panel, this raises two questions.

    1. Why do some panels have off-centered holes? I'm guessing to allow for more fall movement.

    2. How exactly does the off-centered hole affect my axis tilt? It made me wonder if I could orient the panel upside down so the lens is above the axis tilt and thereby simulate asymmetrical tilt. I assume asymmetrical tilt works by having the lens above the axis tilt mechanism or have I misunderstood?

    Thanks

  2. #2

    Axis tilts and Ebony with off-centered panel

    The standard Linhof Technika board has an off centered hole. I do not know what the origin of this design is, but that's how it is. The zeroed position on your Ebony takes this into account so that the axis tilt fulcrum is in fact on the optical axis of the lens when it's mounted on a board with an off-centered hole (Ebony boards are off-center). The Ebony front standard has a channel which guides the tilt axis some distance below the actual tilt axis. If you zero the front standrd using the two "dots", your axis tilt will be exactly where it should be.

    Ebony 8X10 cameras in fact have two "zero" positions on the front standard - one for using Linhof type boards with an off-center hole, and one for using Sinar boards (where the hole is exactly in the center).

  3. #3

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    Axis tilts and Ebony with off-centered panel

    The hole in a Technika board is placed so that when the Linhof front and rear standards are at the 0 position the lens is centered on the ground glass.

  4. #4

    Axis tilts and Ebony with off-centered panel

    Bob

    I suppose more useful would be - why is the hole off-centered (i.e. why was the hole designed to be off-centered instead of centered)?

  5. #5

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    Axis tilts and Ebony with off-centered panel

    Don,

    Turn a Linhof board over and note the round light trap that fits the hole in the front standard. Normally the lens is mounted in the center of that hole so it is centered on the ground glass.

  6. #6

    Axis tilts and Ebony with off-centered panel

    News to me - every Linhof board I own (as well as generics like the Ebony boards I use) the hole is off center - lower than the center position of the circular light trap hole. My question was: "why did Linhof design these boards like this"? (I realize that their cameras are designed so that with the correct lensboard, the center of the image from a lens will be on the center of the ground glass - just curious as to why they did that instead of centering everything).

  7. #7

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    Axis tilts and Ebony with off-centered panel

    To better understand the offset hole in Linhof technica boards, if you look at a Technica BELLOWS carefully from the side, it can be noted that the bellows itself is not symmetrical. There is a larger taper to the bottom of the bellows than there is to the top taper of the bellows. So between the offset bellows taper, and the offset hole, the lens will end up being centered in front of the film at a normal starting point. I suspect that this offset of the bellows was chosen by the original engineers to give a better overall rise as well as front tilt capability to the Technica series.

    If you use a Technica board on a non-Technica camera, it could indeed put the lens off-center. (I had an adapter for a Sinar for Technica boards, if the makers of the adapter were smart, they might have offset the mount location to re-center the lens hole.)

    (Really Bob, I think you should have caught this one!)

  8. #8
    Photographer, Machinist, etc. Jeffrey Sipress's Avatar
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    Axis tilts and Ebony with off-centered panel

    So, officially, what is the distance of the offset?

  9. #9

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    Axis tilts and Ebony with off-centered panel

    Nick,

    In answer to your question 2.) I don't know about your Ebony, but on a Linhof you definitely cannot turn the board upside down, it is not symmetrical in regard to location tangs etc. Additionally the two bottom corners of the lens board are chamfered at an angle. Those are to allow for the shape of the "U" uprights on Technica cameras which are thicker here for strength. A tech board on a tech camera, really only rest at three points, one at each of the location notches, and one at the center of the top.

    In looking critically at my Master Technica this morning, I conclude that the reason for the offset does not really have any movement inspired origins. It appears it exists simply to make the camera as compact as possible. The front standard rides on top of the tracks of the drop bed. Within 3/4 of an inch of space, there is the clamp to the rail, swing, shift and the thickness of the bottom of the "U" upright. From this point back to the film plane, if the bellows were made with a symmetrical taper, the top of the camera could well be nearly 3/4 of an inch taller (bigger).

    A careful examination of the Technica front standard will also reveal that the tilt center is definitely below the center line of the round hole which accepts the lens shutter. That tilt center should coincide with the offset hole on the lens board.

    Jeffrey, I don't know the official distance, but at eyeball, it looks close to 3/8 of an inch. Perhaps SK Grimes or someone else who machines shutter holes might share the official distance with you.

  10. #10

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    Axis tilts and Ebony with off-centered panel

    One thing to add. The shutter hole does not HAVE to be drilled offset on the board. I have one in my desk which is actually centered. I had used it on an adapter to my Sinar. The one I have here is for 0 Copal. If you are interested in an exchange for your offset board, contact me offline.

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