Types of dust spots in images

Discussion in 'Digital SLR' started by Rich, Sep 27, 2005.

  1. Rich

    Rich Guest

    There are around a dozen dust spots in this 5D image. I'm wondering
    why some are irregular while others appear very round. It's almost
    like they are being imaged off different surfaces and that the round
    ones are diffraction patterns of spots too small to actually resolve
    as actual dust particles.
    -Rich

    http://dc.watch.impress.co.jp/cda/parts/image_for_link/31744-2346-14-1.html
     
    Rich, Sep 27, 2005
    #1
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  2. I don't understand Japanese but I understand a lot about digital images
    and their faults. I examined this image and another offered from the
    same site by someone in digital.slr a few days ago.

    This image (and the other one) has very clear evidence of the problems
    which might face 5D owners. Chromatic Aberrations and purple fringing
    are the bane of digital photographers. The more tightly packed the
    sensor, the more likely to get the faults.

    Sigma and Tokina both produce "designed for digital" lenses. The Tokina
    effort produces pretty poor quality images when used on a 35mm film
    camera but good to excellent when used on a DSLR. I haven't used the
    Sigmas. But having the light rays fall at 90 degrees to the sensor can
    only benefit DSLR images.

    Seeing as the world at large is yet to pass judgment on the 5D, I guess
    we'll have to wait and see how good (bad?) the sensor design is at
    preventing purple fringing. These early photos are certainly not good news.
     
    Pix on Canvas, Sep 27, 2005
    #2
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  3. Maybe they're tiny pieces of plastic?
     
    Randall Ainsworth, Sep 27, 2005
    #3
  4. Rich

    Norm Dresner Guest

    Dust motes are tiny pieces of many different substances that flake off by a
    fracture failure of the top layers of the (usually) crystalline surface.
    There's absolutely no reason to expect any uniformity of size or shape.

    That said, there are, as you suggest, many different surfaces inside a
    camera from which unwanted images can form ranging from the surface of the
    sensor itself to the front, rear, and even internal surfaces of the lens,
    diaphragm blades, etc.

    Norm
     
    Norm Dresner, Sep 27, 2005
    #4
  5. Rich

    tomm101 Guest

    A couple of questions about this image.
    1)Are you sure it was taken with a 5D, the name of the image is
    12-24-Kodak-standard.jpg why?
    2) the image was taken with a 12-24 f4.5-5.6 lens at 12mm, this is a
    Sigma lens not a Canon.
    Could this have been taken with a Kodak DCS-N or C? Name of the file
    seems to suggest that, would explain a lot of the aberations.
    Check Luminos Landscape on the latest user (not quite)review of the 5D.

    Tom
     
    tomm101, Sep 27, 2005
    #5
  6. The file name is odd but the EXIF data says Canon 5D, conversion using Canon
    DPP and pixel count 4368 x 2912, which fits with the 5D sensor.

    Mike Bernstein
     
    Mike Bernstein, Sep 27, 2005
    #6
  7. Rich

    tomm101 Guest

    Checked the EXIF, was the Canon 5D. The Luminos Landscape article
    mentioned that he had to clean the sensor more than other cameras, and
    this sensor sure could have used a cleaning.
    What was the thing about CA in this pic, took it up to 300% and we
    could hardly find any, and that could have been atributed to jpeg
    compression.
     
    tomm101, Sep 27, 2005
    #7
  8. Rich

    no_name Guest

    Well, a REAL (TM) photographer would use T-grain dust motes, so they
    would be uniform size and shape.
     
    no_name, Sep 27, 2005
    #8
  9. Rich

    Rich Guest

    Not even Canon would put much plastic in a $3500 camera body, if they
    wanted it to sell, that is.
    -Rich
     
    Rich, Sep 28, 2005
    #9
  10. Don't count on it!
     
    Pix on Canvas, Sep 28, 2005
    #10
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