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Thread: Still life - DOF problem

  1. #1

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    Still life - DOF problem

    As test for learning how to develop my film I took a still life, also now as we cannot go out this will be my subject for a while.

    The setup 4X5 Chamonix, with 150/5.6 lens Aperture f45.
    Distance to te flowers about 20”
    The distance between the flowers and the frame about 10”

    I cannot get the two sharp, I’m I doing something wrong or is this not possible. Normally I do landscape or architecture.

    Click image for larger version. 

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    First image focus on the frame, the second image focus on the flowers

    Thx
    Patrick

  2. #2
    C. D. Keth's Avatar
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    Re: Still life - DOF problem

    That may just not be possible on that lens or at that stop. I canít think of anything in the way of movements that would help you out.


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    -Chris

  3. #3

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    Re: Still life - DOF problem

    You seem to have focused on the frame. At the magnification you're working at, DOF is roughly (got that, folks, roughly) symmetrical about the plane of best focus. Try focusing midway between the front of the blooms and the frame.

  4. #4

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    Re: Still life - DOF problem

    Larger aperture to avoid diffraction and take one focused 1/3rd between the flowers and the mirror and one half way between.
    Focusing on the flowers means that you are loosing all of the DOF in front of the flowers.

    Your lens should be diffraction limited at 22.

  5. #5

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    Re: Still life - DOF problem

    Quote Originally Posted by Bob Salomon View Post
    Larger aperture to avoid diffraction and take one focused 1/3rd between the flowers and the mirror and one half way between.
    Focusing on the flowers means that you are loosing all of the DOF in front of the flowers.

    Your lens should be diffraction limited at 22.
    Bob, the 1/3d rule doesn't apply close up. It also doesn't apply at infinity.

  6. #6

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    Re: Still life - DOF problem

    Composition not gonna work for trying to hold focus front to back. Stopping down to f45 or using camera movements will not get front & back "in focus". In this case your best option is to move back, make the composed image smaller on the ground glass then to film. Moving in, close up will greatly aggravate this problem.

    Alternative is to change the composition by placing the tall objects at the back of the image with the shorter items in the front of the image. This is more effective as camera_lens tilt produces a curved plane of focus toward what is considered the back or rear or furthest away object.

    Idea is to arrange a image composition that can be held in reasonable focus with the lens wide open, then apply minimal camera movements to achieve enough improvement in overall focus at full lens aperture. Once these basic criteria are met, then stop down the lens only as much as needed to achieve good-reasonable overall focus_this is done by looking at the GG with the lens stopped down to taking aperture.


    All the best and enjoy this adventure
    Bernice

  7. #7

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    Re: Still life - DOF problem

    Quote Originally Posted by Dan Fromm View Post
    Bob, the 1/3d rule doesn't apply close up. It also doesn't apply at infinity.
    Thatís why I also said half way.

  8. #8

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    Re: Still life - DOF problem

    Just quantify, one DOF calculator online shows DOF at 25" for the 150mm lens at 5.4". Variations in calculating DOF could increase or decrease this number, but it is nowhere close to the 10" you need. LF does have its specific challenges. As Bernice noted, increasing the distance will increase the DOF, but then the relative sizes of the flower group and picture frame, hence their alignment, will also change.
    Philip U.

    Sine scientia ars nihil est. (Without science/knowledge, art is nothing.)
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  9. #9

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    Re: Still life - DOF problem

    Quote Originally Posted by Ulophot View Post
    Just quantify, one DOF calculator online shows DOF at 25" for the 150mm lens at 5.4". Variations in calculating DOF could increase or decrease this number, but it is nowhere close to the 10" you need. LF does have its specific challenges. As Bernice noted, increasing the distance will increase the DOF, but then the relative sizes of the flower group and picture frame, hence their alignment, will also change.
    With what circle of confusion?
    We donít know if the op wants to make a contact print or a mural.

  10. #10
    Drew Bedo's Avatar
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    Re: Still life - DOF problem

    I may not fully understand your creative vision. . . .but I am sure that, as Seinfeld's George Costanza famously said, " Its not you, its ME."

    To get both in focus, I would raise the whole camera some, then use some tilt and stop down. You may be able to get both the frame and the blooms sharp. As sharpness falls off going down the stems it will be less noticeable. It may be that you will have to accept some compromise in this.

    I myself have a visual disability and sharp focus is always a challenge for me. One strategy that I regularly use is to place a target in the composition. I often use a bar code panel from some rtail package. The target is placed in the composition and focus checked. Then the target is moved to another part of the shot and I go back under the dark cloth. This goes on till I get it right or decide to change the set up. One drawback: Sometimes I get so enthusiastic about finally putting the shot together that the target gets left in the shot.

    If you don't see it on the ground glass it is not there.
    Last edited by Drew Bedo; 23-Mar-2020 at 17:25.
    Drew Bedo
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