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Thread: help with focus

  1. #1

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    help with focus

    I need some help here I don't think I am on the right track with my focus. Its very hit or miss. I don't think I am using the movements correctly. I was attempting to have everything sharp in the two attached pics. I closed down to F22 and shot at 1/125 with a 210mm lens. Isn't that enough? Should I be tilting the lens away from the subject to increase DOF. I have two books on large format and try to spend time going through the forum. Any advice in regards to focus would be welcomed.
    Attached Thumbnails Attached Thumbnails focus.jpg   focus #2.jpg  

  2. #2

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    Re: help with focus

    In many cases you can increase your DOF with movements. The methods I was taught require a way to accurately measure the position of the standard you use to focus. Then focus on the nearest thing you want in sharp focus and take note of where the standard is. Then focus on the farthest point you want in sharp focus and look at that measurement. The difference of the 2, in mm multiplied by 5 will give you your widest aperture to have all of that in focus. Then you move the standard to 1/2 way between the 2 extremes and stop down. This method gives you precise control over DOF.

    To use movements it depends whether your front standard has tilt ad swing. Using tilt or swing you change the focal plane in order to reduce the aperture to achieve the desired DOF. If your camera has axial tilt (tilts around a point near the center of the lend board) then you focus on the nearest object then tilt until the farthest object is in focus. Then go back to the near and do it al over again until both are in focus. Then check the measurement as in the near-far method and find the most out of focus object in the glass and focus on it. Taking the difference as before and multiply by 5 you have the minimum aperture setting.

  3. #3

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    Re: help with focus

    Quote Originally Posted by memorris View Post
    In many cases you can increase your DOF with movements. The methods I was taught require a way to accurately measure the position of the standard you use to focus. Then focus on the nearest thing you want in sharp focus and take note of where the standard is. Then focus on the farthest point you want in sharp focus and look at that measurement. The difference of the 2, in mm multiplied by 5 will give you your widest aperture to have all of that in focus. Then you move the standard to 1/2 way between the 2 extremes and stop down. This method gives you precise control over DOF.

    To use movements it depends whether your front standard has tilt ad swing. Using tilt or swing you change the focal plane in order to reduce the aperture to achieve the desired DOF. If your camera has axial tilt (tilts around a point near the center of the lend board) then you focus on the nearest object then tilt until the farthest object is in focus. Then go back to the near and do it al over again until both are in focus. Then check the measurement as in the near-far method and find the most out of focus object in the glass and focus on it. Taking the difference as before and multiply by 5 you have the minimum aperture setting.
    Thanks for pointing me in the right direction.

  4. #4

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    Re: help with focus

    If you're trying to use front tilt to increase depth of field along the ground, you would tilt the lens standard forward. However, you would have to take care that you don't lose clarity in the tops of the distant trees, because you are tilting the cone of sharp focus downward.

    I was taught a simple poem:

    "Focus for far, tilt for near.
    Focus and tilt 'til all is clear"

    And one rule:
    Watch the groundglass, which tells all.

  5. #5

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    Re: help with focus

    focus on trees with knob
    tilt for river bank
    focus again on trees with knob
    focus again on river bank using slight adjustment of tilt

    this leaves the center section between the trees and river bank -the river- not well focused
    smaller stops f22, f32 and f45 make the river -center section- sharp
    check the rock to see which to use
    then use a little more lol

  6. #6
    mandoman7's Avatar
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    Re: help with focus

    Its tedious, but a loupe should really be used if you're having focus problems. It takes more time, but it pays off for the beginning worker.
    John Youngblood
    www.jyoungblood.com

  7. #7

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    Re: help with focus

    Thanks everyone, I wish steve simmons and leslie stroebel were as clear as that in their books.
    I will be out as soon as the weather improves here in the northeast putting these suggestions to work. Once again I am thankful for the help I have received form this forum. Rick

  8. #8
    Jacques-Mtl's Avatar
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    Re: help with focus

    Maybe you can have a look at that page http://www.largeformatphotography.info/ there's a link on how to focus the camera.
    Jacques

  9. #9

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    Re: help with focus

    Quote Originally Posted by Jacques-Mtl View Post
    Maybe you can have a look at that page http://www.largeformatphotography.info/ there's a link on how to focus the camera.
    Jacques
    Thanks Jacques I have bookmarked the page.

  10. #10

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    Re: help with focus

    If you are just starting out:

    1. Put the loupe on the bottom of the ground glass and focus (that is "focus far")
    2. Then put the loupe on the top of the groundglass and tilt the front standard forward [or the rear standard backward] (that is "tilt near").
    3. Then fine focus on the bottom of the groundglass
    4. Then fine tilt the front standard
    5. Then repeat if need be for enough iterations to get things right


    The area between the far and near will probably be unsharp. You must stop down sufficiently to bring the middle into focus. F22 on your setup might be insufficient. Don't be afraid to "bracket" with f32, f45, or (if possible) f64 and then evaluate the processed negatives with a loupe to get a feel for the differences and see if diffraction at small apertures results in any visible degradation in sharpness with your setup (I doubt it will).

    When you focus far, tilt near, you have to be careful about vertical objects like trees that are in the middle of those two planes. They can be difficult to render sharply and require a small aperture.

    Also, sometimes a very small swing can improve the left-right depth of field but you will occasionally screw up everything and have to zero out all the movements and start over. Don't get frustrated and keep repeating until you get the hang of it. I'm no expert but that is how I go about it.

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