Determining resolution of aerial pictures

Discussion in 'Photography' started by c0, Jan 31, 2004.

  1. c0

    c0 Guest

    We're trying to figure out what type of resolution you would likely get
    with a camera flying about 10,000 above the ground, with a 6" lens using
    large format film. That all I know, but would appreciate any general
    guidelines or guesses.

    Thanks in advance.
    c0, Jan 31, 2004
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  2. This sounds like a trick question.

    "Film resolution" has nothing to do with altitude.
    "Resolving power" -- how small an object on the ground can you identify
    clearly may be the question you're asking. I have a family member who does
    aerial photography for a living so may be able to answer this question.
    Larry CdeBaca, Feb 1, 2004
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  3. c0

    sQuick Guest

    The resolution would be the same at 10,000 ft as it would a 1ft

    sQuick, Feb 1, 2004
  4. c0

    c0 Guest

    What could you likely see from 10,000 feet, a dime?
    c0, Feb 1, 2004
  5. c0

    Chris Guest

    That's got nothing to do with "resolution", but "image amplification".

    If you see aim a lens with similar optical characteristics to the human eye
    at a dime-size object from 10,000 feet away, you'd be lucky to see a glint
    the size of a grain of sand. But, magnify that view, and it'll be abit

    It's not your resolution, but your zoom/magnification that matters. Of
    course, if your resolution is distorted or otherwise substandard to begin
    with, all the lens in the world isn't going to help.

    Start with a good camera, and build upon that with a good lens.
    Chris, Feb 1, 2004
  6. There are two limits here: the film and the lens.

    Film resolution tops out about 4000 dpi. Multiplying
    this by the size of the exposed film gives you a
    total resolution. Divide this into the size of your
    ground footprint, it will give you the smallest
    possible resolvable item on the ground.

    That number will then be restricted by the sharpness
    of the lens and by how much you can zoom in (obviously,
    the smaller your ground footprint, the higher the
    effective resolution).
    Hugh Bothwell, Feb 1, 2004
  7. c0

    Norman Worth Guest

    There are three big factors in determining the ground resolution of a lens:
    magnification, lens resolution, and film resolution. Magnification is
    determined by the focal length and the altitude (5*10^-5 in this case).
    Lens resolution depends on lens design and f-stop. Most aerial camera
    lenses resolve near their defraction limits for reasonable apertures. For
    f/8 that would be about 185 lines per mm. Figure 150 lines per mm. Film
    resolution depends on the contrast of the object, the design of the film,
    and the processing. Representative figures are 125 lines per mm for 1000:1
    contrast and 50 lines per mm for 1.6:1 contrast. The resolutions of the film
    and the lens must be combined to get a net resolution. Using the reciprical
    of the sum of the reciprocals method, this gives 68 lines per mm for high
    contrast 37.5 line per mm for low contrast. Applying the magnification, you
    will resolve about 300 mm (1 foot) on the ground for high contrast items,
    533 mm (21 inches) for low contrast items. Notice there are a lot of
    assumptions in these calculations: f stop, quality of the lens, quality of
    the film, perfection of the other conditions.
    Norman Worth, Feb 1, 2004
  8. c0

    Marty Guest

    Not sure if it might help, but do a search for USAPhotoMaps, you can
    download a program, look at the zoom feature, I believe the resolution
    of their aerial photos is something like 1 meter/ pixel
    Marty, Feb 2, 2004
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