Newbie Query on CCD resolution

Discussion in 'Amateur Video Production' started by Maurice Northey, Sep 9, 2003.

  1. Does anyone know how the CCD resolution affects picture quality?
    - on MiniDV tapes
    - and on VCDs created from the tapes

    Given that MiniDV format has a fixed resolution is buying a DV
    camcorder with a CCD resolution > 800,000 a waste of money -
    especially if I then copy the tape to CD or DVD?

    Is the CCD resolution only relevant for jpegs?

    tia

    MN
     
    Maurice Northey, Sep 9, 2003
    #1
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  2. Maurice Northey

    Juan Lauda Guest

    Given that a PAL DV frame (720 x 576) has a resolution of ~400K pixels,
    anything more than this would indeed appear to be a waste of money.
    However, the excess resolution can be used to "oversample" when capturing
    the frame. An 800K CCD captures twice as much detail as a 400K CCD.
    The 800K image can be processed (downsampled) to give a better quality 400K
    image than the raw image from the 400K sensor.
    Camcorders with image stabilisation (steady shot) use some of the extra
    pixels for this facility.
    My own camcorder (Sony DCR-PC105e) has a mega-pixel CCD and the extra pixels
    can be used to capture in 16:9 widescreen format. The extra horizontal
    resolution is then downsampled by the camcorder to "squeeze" the 16:9 frame
    image into a standard 720x576 PAL frame.
    At the end of the day if the camcorder has a poor quality lens that cannot
    resolve detail beyond 400K pixels then the "larger" CCD is not going to help
    much.
    Look for detailed reviews by camcorder magazines for an indication of the
    quality of the lens.
    Also, any detail preserved by using a higher resolution CCD may be lost if
    the DV movie is then recoded for DVD at a low bit rate.

    I've never used a DV camcorder with a low resolution CCD so I can't comment
    on whether the quality is acceptable, but I can tell you that the ability to
    record in "true" 16:9 widescreen mode without compromising vertical
    resolution (letterboxing) is worth every penny to me.
     
    Juan Lauda, Sep 9, 2003
    #2
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  3. Maurice Northey

    Sanman Guest

    I have a Sony TRV-103 D8 Camera that has 460K but only uses 290K of those
    for the image. The picture quality is very good, approaching some low end 3
    chip models. The signal processing has a lot to do with that. One thing
    you do notice with these low res CCDs is the color aliasing, those annoying
    color bands that appear on horizontal parts of the image. It gets worse
    indoors, say, in my kitchen, where the edge of the counter top has blue and
    yellow color bands along the edge. Even a Panasonic that I played with had
    680,000 total pixels and still had some of the above problem. I once had a
    Sony CCD-V9 back in 1990 and it had 380K (310K for picture). You couldn't
    get this thing to alias no matter what you shot. What did they ever do with
    THAT CCD chip? Anyway, apart from the annoying aliasing, these 290K pixels
    on the TRV-103 produce an image too good to be true, and outside, you hardly
    notice any aliasing, if at all.

    Sanman
     
    Sanman, Sep 10, 2003
    #3
  4. Maurice Northey

    Juan Lauda Guest

    Even 5MP digital still cameras suffer from color aliasing on high contrast
    images (purple fringing usually).
     
    Juan Lauda, Sep 10, 2003
    #4
  5. Maurice Northey

    Sasha Guest

    Likely that CCD resolution have nothing to do with it -- the problem is in
    lenses, the effect is called chromatic aberration.

    http://ray.cg.tuwien.ac.at/rft/Photography/TipsAndTricks/Aberration/
     
    Sasha, Sep 11, 2003
    #5
  6. This question comes up often - search on google.
    Short answer: higher CCD pixel count *does* affect
    motion-video image quality (for both good and ill...).
     
    David Ruether, Sep 11, 2003
    #6
  7. Maurice Northey

    Juan Lauda Guest

    Your right in that CCD resolution has nothing to do with it (which is why I
    pointed out that 400K DV CCDs and 5MP DSC CCDs suffer in the same way).

    However I disagree with your assertation that this is due to chromatic
    abberration, or prismatic effects in the less elements.

    Purple fringing in digital cameras or camcorders is mainly due to
    "blooming", ie electrical charge leaking from brightly lit CCD elements to
    neigbouring unlit CCD elements. It manifests itself in areas of high
    contrast because this is where brightly lit elements occur adjacent to unlit
    elements.
     
    Juan Lauda, Sep 11, 2003
    #7
  8. Maurice Northey

    FLY135 Guest

    Since each CCD element can only capture one color, having more elements than
    pixels in the output image is not a waste. Also the color aliasing is
    probably partly due to the conversion of the CCD elements into color pixels.
    The CCD elements have color filters and normally half of the elements are
    green while blue and red each are allocated 25%. An algorithm such as
    indicated in the following link is used to convert to RGB pixels. At least
    that's my experience with still digital cameras. I'm assuming that
    camcorders work the same way.

    http://www4.ncsu.edu:8030/~rramana/Research/demosaicking-JEI-02.pdf
     
    FLY135, Sep 11, 2003
    #8
  9. Maurice Northey

    Sanman Guest

    Ok hang on here. We're talking about the wrong kind of fringing here. I
    was referring to the mulit-colored fringing that happens on fine horizontal
    images like care pinstriping, or horizontal blinds. It's called aliasing.
    It happens on most single CCD camcorders. It's annoying, and hopefully when
    I buy a camcorder with a 1 MP CCD, I'll be rid of it.

    Sanman
     
    Sanman, Sep 12, 2003
    #9
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