Resolution

Discussion in 'Digital Photography' started by Tony M, Aug 14, 2005.

  1. Tony M

    Tony M Guest

    My 4Mp P&S can record at 4 different resolutions:

    2304 x 1728 (4Mp)
    1600 x 1200 (~2Mp)
    1280 x 960 (~1.4Mp)
    640 x 480 (~0.3Mp)

    Presumably the size of the sensor approximates to the highest resolution.

    How are the lower resolutions obtained? ie at 1600x1200 are 50% of the
    pixels discarded or is a smaller area of the sensor used?

    Before anyone mentions it - Yes - I always use the highest resolution
    and minimum compression!

    Tony M
     
    Tony M, Aug 14, 2005
    #1
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  2. Tony M

    Jim Guest

    "Tony M" <> wrote in message
    news:ddo819$91g$...
    > My 4Mp P&S can record at 4 different resolutions:
    >
    > 2304 x 1728 (4Mp)
    > 1600 x 1200 (~2Mp)
    > 1280 x 960 (~1.4Mp)
    > 640 x 480 (~0.3Mp)
    >
    > Presumably the size of the sensor approximates to the highest resolution.
    >
    > How are the lower resolutions obtained? ie at 1600x1200 are 50% of the
    > pixels discarded or is a smaller area of the sensor used?

    Perhaps your camera just discards the unwanted pixels. Perhaps it uses some
    kind of interpolation schem to reduce the resolution. Perhaps it uses some
    other method, but it would be very unlikely to reduce the are of the sensor
    (that operation is called digital zoom).
    Jim
    >
    > Before anyone mentions it - Yes - I always use the highest resolution and
    > minimum compression!
    >
    > Tony M
     
    Jim, Aug 14, 2005
    #2
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  3. Tony M <> wrote:
    : My 4Mp P&S can record at 4 different resolutions:

    : 2304 x 1728 (4Mp)
    : 1600 x 1200 (~2Mp)
    : 1280 x 960 (~1.4Mp)
    : 640 x 480 (~0.3Mp)

    : Presumably the size of the sensor approximates to the highest resolution.

    : How are the lower resolutions obtained? ie at 1600x1200 are 50% of the
    : pixels discarded or is a smaller area of the sensor used?

    : Before anyone mentions it - Yes - I always use the highest resolution
    : and minimum compression!

    : Tony M

    The image area remains the same for all modes. So the reduction in
    resolution either is a reduction of pixels read or a mathematical
    averaging of several pixels into a single one, or some other software
    reduction. But the overall area of the sensor that is capturing the image
    remains constant. So an image of an object that exactly fills the image at
    one resolution will still exactly fill the image at all the resolutions. A
    reduction in the area would give the effect of zooming in (digital zoom).

    Randy

    ==========
    Randy Berbaum
    Champaign, IL
     
    Randy Berbaum, Aug 15, 2005
    #3
  4. Tony M

    Don Stauffer Guest

    Tony M wrote:
    > My 4Mp P&S can record at 4 different resolutions:
    >
    > 2304 x 1728 (4Mp)
    > 1600 x 1200 (~2Mp)
    > 1280 x 960 (~1.4Mp)
    > 640 x 480 (~0.3Mp)
    >
    > Presumably the size of the sensor approximates to the highest resolution.
    >
    > How are the lower resolutions obtained? ie at 1600x1200 are 50% of the
    > pixels discarded or is a smaller area of the sensor used?
    >
    > Before anyone mentions it - Yes - I always use the highest resolution
    > and minimum compression!
    >
    > Tony M



    No, the pixel values are not discarded, they are averaged. While the
    process is more complicated than this, here is at least an approximation
    of the process. Lets say we are downsampling by a factor of two
    linearly, i.e, a 4X reduction in total pixels. Start at the top left.
    The first two leftmost pixels in the top row and the second row are
    averaged. This average value is assigned to the top left pixel of the
    new, downsampled array.
     
    Don Stauffer, Aug 15, 2005
    #4
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