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Thread: Fixed focus 4x5 camera

  1. #21
    Jac@stafford.net's Avatar
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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by Pfsor View Post
    No, adding 2 or 3 measurements is not difficult, indeed. To take the 2 or 3 measurements is much more difficult, because of the practical difficulties you encounter. Where do you take the measure of the distance between the gg and the lens flange? Where do you put the calliper when the gg is inside the camera box and you calliper is outside of it? While measuring on the outside frame of the gg do you take into account the manufacturing imprecision you find on it? Before you add the 2 or 3 measurements you must find how precise you are when fiddling with you callipers on different parts of your "complete springback". Because the complete springback is not built to 0.01mm tolerance all over, you will soon discover.
    And then - if you think your gg plane can go off one side with 2.4mm and be happy then build such a camera for 65mm lens and be happy... When you focus your 65mm lens, moving the gg 2.4mm gives you the same focus, under your focusing loupe, doesn't it? It's just adding 2 or 3 measurements together, isn't it? After all, a camera is just a light tight box between a lens and gg, isn't it?
    I think, Dan is intelligent enough to know the difference between saying a theory and following it in the practical way.
    Do not worry so much for precision. You are on track. Make it the best you can and be happy. The pictures matter a whole lot more than technical minutiae.

  2. #22

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    Re: Fixed focus 4x5 camera

    Jac, don't worry, I will still sleep well.

  3. #23

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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by Jac@stafford.net View Post
    Steve, finding shims has always been a problem for me.
    OR, make a proper square lensboard (wood, metal etc) that will fit on the front of your shortened camera, and allow space for a foam or other soft gasket to make a limited range collapsible "bellows", and have screws on the four corners that you can tweak to find your favorite focusing distance... You might even be able to add some on-the-fly focusing arrangement for at least some different focusing zones...

    You could also come up with some way to mount different length lens cones for different FL's that can be screwed down at will...

    Steve K

  4. #24

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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by Pfsor View Post
    Hmm. And the foam or other soft gasket will get pressed more and more in the time passing or will just keep the same dimension? Seems like a great idea to make your FFD differ while seasons flow.
    Nah, the heads of the screws holding it down in the corners are the register points, the foam or rubber just fills the gap and create outward pressure...

    Steve K

  5. #25

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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by Pfsor View Post
    Where do you put the callipers when the gg is inside the camera box and you calliper is outside of it?
    Funny that you should ask. What I've done has been to mount the lens in question on a Speed Graphic board, put it on (surprise!) a Speed Graphic, focus to the desired distance, take the lens off, a drilled board with no lens on the camera and measure the flange-to-film distance with a depth gauge. The OP may have to borrow a camera to do this. Speed Graphic not necessary, it was what I had at the time.

    Its better than guessing, which is what using published flange-focal distances amounts to. Published flange-focal distances are great for finding out what can probably be done but that's not what the OP needs.

    About the need for focusing. The shortest lens I've had -- still have it -- for 35 mm is a 24 mm. It has to be focused for best results. My 35 Apo-Grandagon has to be focused for best results.

  6. #26

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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by Dan Fromm View Post
    Funny that you should ask. What I've done has been to mount the lens in question on a Speed Graphic board, put it on (surprise!) a Speed Graphic, focus to the desired distance, take the lens off, a drilled board with no lens on the camera and measure the flange-to-film distance with a depth gauge. The OP may have to borrow a camera to do this. Speed Graphic not necessary, it was what I had at the time.
    And the second lens board must have the exact same thickness (best to 0.01mm) and geometry as the first one and the depth gauge must not be inclined on it in any direction so that the measure is not false and the standard may not move at all (to the precision of 0.01mm) and all added you're in the situation that taking the measure 5x you get 5x different results... Been there, done that.
    How much easier to build a camera where fine focusing of the lens plate takes care of the excellent result without asking the depth gauge its opinion.
    Or you can can just say - I have 2.4mm of free space, what do I care about precision, ain't any naysayer, don't need any atomic clock and am happy...
    To each his own.

  7. #27

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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by LabRat View Post
    Nah, the heads of the screws holding it down in the corners are the register points, the foam or rubber just fills the gap and create outward pressure...

    Steve K
    Ok Steve, got that even before I deleted my post. No need to fill the gap and create outward pressure. You first build the box and fasten down the screws in their correct position - if you know how to - and then cover the box from one standard to the other with whatever suitable light tight material. My preference was black leather - lighter than anything else and interesting photo look is assured.

  8. #28

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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by Pfsor View Post
    And the second lens board must have the exact same thickness (best to 0.01mm) and geometry as the first one and the depth gauge must not be inclined on it in any direction so that the measure is not false and the standard may not move at all (to the precision of 0.01mm) and all added you're in the situation that taking the measure 5x you get 5x different results... Been there, done that.
    How much easier to build a camera where fine focusing of the lens plate takes care of the excellent result without asking the depth gauge its opinion.
    Or you can can just say - I have 2.4mm of free space, what do I care about precision, ain't any naysayer, don't need any atomic clock and am happy...
    To each his own.
    Interesting. The OP has three posts in this discussion. In none of them does he mention making a camera with a ground glass. Your approach will certainly work with a camera in which focus can be seen and adjusted.

    Oh, and by the way, the OP says he has a Sinar. He didn't say that his lens is on a Sinar board. If it isn't, he can get a board drilled to suit the lens, put the lens on the board, mount on the Sinar, focus ...

  9. #29

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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by Dan Fromm View Post
    Interesting. The OP has three posts in this discussion. In none of them does he mention making a camera with a ground glass. Your approach will certainly work with a camera in which focus can be seen and adjusted.
    .
    Interesting. How would you control the focus if not on a gg? Trying the focus on film each time you want to adjust the FFD and see what it does? Would be a highly original approach, it seems. The OP wants to try a simple fixed focus camera. Must be simple to do that, I suppose. Just add his lens on a fixed focus box and voilą...

  10. #30

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    Re: Fixed focus 4x5 camera

    Quote Originally Posted by Pfsor View Post
    Interesting. How would you control the focus if not on a gg? Trying the focus on film each time you want to adjust the FFD and see what it does? Would be a highly original approach, it seems. The OP wants to try a simple fixed focus camera. Must be simple to do that, I suppose. Just add his lens on a fixed focus box and voilą...
    As you said in post #26 above,

    How much easier to build a camera where fine focusing of the lens plate takes care of the excellent result without asking the depth gauge its opinion.

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