Depth of field and the subjects distance

Discussion in 'Photography Beginners' Forum' started by kkamin, Dec 15, 2009.

  1. kkamin

    kkamin TPF Noob!

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    Why is there less depth of field when an object is closer to the camera?

    Thanks,
    Kkamin
     
  2. im_jacobf

    im_jacobf TPF Noob!

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    It's blocking the rest of the picture? Haha, just kidding. Uhm, I don't understand what you are asking. The camera focuses on the thing in its focus-range. That's where the F-stops come in, they adjust the opening of the aperture which affects the DOF.

    I honestly have no idea wtf you are asking, though.
     
  3. kkamin

    kkamin TPF Noob!

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    If you focus on something 5 feet from the camera you have x amount of depth of field, if you remain at the same f/stop but focus on something 30 feet from the camera, you'll have more depth of field. why?
     
  4. Bitter Jeweler

    Bitter Jeweler Been spending a lot of time on here!

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  5. Derrel

    Derrel Mr. Rain Cloud

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    The Wikipedia article really goes into a LOT of the nuances of depth of field, but the Bob Atkins article here Bob Atkins Photography

    might be more accessible to most people who don't have advanced mathematics degrees. One of the nice things about the Atkins article is that is does a good job of pointing out that depth of field differs between format sizes, and that depth of field tends to increase very rapidly past a "certain distance".

    At very close distances, as the Wikipedia article points out, depth of field is virtually the same between lenses of the same focal length, and depth of field is really more related to image magnification, rather than focal length. When I first heard that, I hardly believed it, but I tried making some 1:1 shots of a miniature camera I have (about 3 inches tall) using a 60mm Nikon macro lens and a Sigma 180mm macro,and at 1/2 life size to 1:1 life-size, the actual amount of depth of field was virtually the same between the lenses. Weird. This is the "close-up condition" aspect of depth of field.

    Moving out to a few feet, and into the 10-12 foot range, depth of field increases rapidly with each foot of distance; as the focusing distance gets past 25-30 feet, depth of field increases are really,really rapid.

    As the Bob Atkins article points out, depth of field's behavior is different under three conditions, shown in his 3-color chart. The conditions are 1) close-up conditions and 2) Intermediate Conditions which are not macro and not close to hyperfocal distance situations and 3) Distances which ARE close to hyperfocal distance situations.

    I think the Atkins article might be worth wading through for people wondering what all the fuss about Full Frame versus 1.6x is all about; it's not an easy subject to talk about without a lot of hardcore mathematical formulas, but the Atkins article has some real gems in it.
     

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