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Thread: Sinar F2: Setting Plane of Focus vs. Setting Depth of Field

  1. #1

    Join Date
    May 2015
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    38

    Sinar F2: Setting Plane of Focus vs. Setting Depth of Field

    Hello everyone,

    just starting out with LF photography and recently acquired a wonderful Sinar F2. Now, I'm somewhat confused when it comes to determining the Plane of Focus and setting the Depth of Field. Here's my problem:

    For both PoF and DoF, I use the methods as described in the Sinar F2 manual. But once I've set the PoF most of the image turns quite sharp (Scheimpflug rule). This makes it quite difficult to determine the optimum DoF/Aperture, since most of the image is already considerably sharp. How do you determine the DoF after setting the PoF?

    I assume that I'm either making a mistake along the way or that my "concept" of finding the optimal aperture is wrong.

    Thanks for your help everyone!

  2. #2

    Join Date
    Aug 2013
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    Brazil - Rio Grande do Sul
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    813

    Re: Sinar F2: Setting Plane of Focus vs. Setting Depth of Field

    Hi Celtic,

    I'm also a lucky owner of a F2, congrats, it's a great camera. I use the dotted line on the ground glass for far-near focus placement with the DOF scale in the rear standard, everything goes flawlessly. Otherwise, if you have composed the image, and found the results of your PoF placements are ok, the diffraction limit of the lens is your guide for optimum lens rendering. If you have room for near wide-open shots with satisfying DoF, in general, the sharpest results can be achieved with when the lens is closed 2-3 f-stops from wide open. This is both an observation of available MTF charts and also observed results on the field. There is a large group of Sinar camera owners around here which will also help you to kickstart with the camera operation and its caveats,

    Cheers,

    Renato

  3. #3

    Join Date
    Mar 2002
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    Sweet, ID
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    517

    Re: Sinar F2: Setting Plane of Focus vs. Setting Depth of Field

    Your procedure is right so far. You still have points off of the PoF that need to be brought into acceptable focus using DoF (f-stop), is just that those points now might be in a different place in your image scene. Instead of a near rock and a distant mountain, it might now be the same rock but the top of tree in the middle ground. What you've hopefully done is made the focus difference between the near and far focus points less such that less extreme (smaller) f-stop is needed to bring them into acceptable focus. Acceptable focus is dependent on what the outcome of your image will be, the larger (projection or print) will require more stringent focus (therefore smaller f-stop). I use Stephen Peterson's approach wherein he actually shows that there is an "optimal" f-stop that minimizes subject blur due to out-of-focus and also considering diffraction. I've attached his three page article, hopefully it helps. After determining dV (using a loop and you'll need a scale on your camera bed/rails) I focus at dV/2. There are most likely less technical ways of understanding and using this, but being an engineer (retired) I like the technicallity LOL! Good luck.
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    The only trouble with doin' nothing is you can't tell when you get caught up

  4. #4

    Join Date
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    Re: Sinar F2: Setting Plane of Focus vs. Setting Depth of Field

    Paul Hasma is a better read for more practical implementation but the two follow the same lens theory. I exchanged emails with Paul many many moons ago on this subject.

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    And of course QT's info
    http://www.largeformatphotography.in...-to-focus.html
    http://www.largeformatphotography.info/fstop.html
    The only trouble with doin' nothing is you can't tell when you get caught up

  5. #5
    Drew Wiley
    Join Date
    Sep 2008
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    SF Bay area, CA
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    16,780

    Re: Sinar F2: Setting Plane of Focus vs. Setting Depth of Field

    I knew all that once, for about the first week I owned a Sinar. For the next thirty-five years I forgot all that and took pictures instead.

  6. #6
    http://www.spiritsofsilver.com tgtaylor's Avatar
    Join Date
    May 2006
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    4,665

    Re: Sinar F2: Setting Plane of Focus vs. Setting Depth of Field

    See post #6 for a practical working example in the field: http://www.largeformatphotography.in...0591&viewfull=

    Thomas

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