Zoom Clarification

Discussion in 'Digital Photography' started by Ed Mullikin, Nov 25, 2006.

  1. Ed Mullikin

    Ed Mullikin Guest

    A point of confusion: For example, what does zoom 6.7X mean? Is that the
    multiplier if one uses the smallest to the largest image a camera can
    record? What is the reference? A friend of mine asked me and I'm not
    certain that I told her correctly.
    Ed Mullikin, Nov 25, 2006
    #1
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  2. Ed Mullikin wrote:
    > A point of confusion: For example, what does zoom 6.7X mean? Is that
    > the multiplier if one uses the smallest to the largest image a camera
    > can record? What is the reference? A friend of mine asked me and
    > I'm not certain that I told her correctly.


    It's usually the ratio of the maximum focal length to the minimum. So a
    25 - 100mm zoom lens might be described as a 4:1 zoom. The area covered
    would have a 16:1 ratio. This is /not/ the same as the "magnification" of
    binoculars.

    David
    David J Taylor, Nov 25, 2006
    #2
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  3. Ed Mullikin

    Ed Mullikin Guest

    That makes sense. My Sony DSC-F828 then can optically zoom 7.1 (from 28 to
    200mm). According to the instruction book I can also get into "Digital Zoom"
    and "Precision Digital Zoom" which serves to confuse me and I've not really
    needed to use it. Thank you.

    "David J Taylor" <-this-bit.nor-this-part.uk>
    wrote in message news:OAZ9h.6705$...
    > Ed Mullikin wrote:
    >> A point of confusion: For example, what does zoom 6.7X mean? Is that
    >> the multiplier if one uses the smallest to the largest image a camera
    >> can record? What is the reference? A friend of mine asked me and
    >> I'm not certain that I told her correctly.

    >
    > It's usually the ratio of the maximum focal length to the minimum. So a
    > 25 - 100mm zoom lens might be described as a 4:1 zoom. The area covered
    > would have a 16:1 ratio. This is /not/ the same as the "magnification" of
    > binoculars.
    >
    > David
    >
    Ed Mullikin, Nov 25, 2006
    #3
  4. "Ed Mullikin" <> wrote in message news:UWZ9h.3167$%...
    > "David J Taylor" <-this-bit.nor-this-part.uk> wrote in message
    > news:OAZ9h.6705$...
    >> Ed Mullikin wrote:


    >>> A point of confusion: For example, what does zoom 6.7X mean? Is that
    >>> the multiplier if one uses the smallest to the largest image a camera
    >>> can record? What is the reference? A friend of mine asked me and
    >>> I'm not certain that I told her correctly.


    >> It's usually the ratio of the maximum focal length to the minimum. So a 25 - 100mm zoom lens might be described as a 4:1 zoom.
    >> The area covered would have a 16:1 ratio. This is /not/ the same as the "magnification" of binoculars.
    >> David


    > That makes sense. My Sony DSC-F828 then can optically zoom 7.1 (from 28 to 200mm). According to the instruction book I can also
    > get into "Digital Zoom" and "Precision Digital Zoom" which serves to confuse me and I've not really needed to use it. Thank you.


    "Digital zoom" involves increasing the appearance of magnification by
    cropping the image area used of the sensor. As you might expect, this
    reduction of the sensor area used reduces the pixel count and therefore
    results in an image that is less sharp and more "pixelated". Most choose
    not to use digital zoom once the results are seen (except possibly in
    moderation, for small prints).
    --
    David Ruether


    http://www.ferrario.com/ruether
    David Ruether, Nov 25, 2006
    #4
  5. Ed Mullikin

    Prometheus Guest

    In article <0I_9h.31817$>, David Ruether
    <> writes
    -----------------cut-------------------
    >"Digital zoom" involves increasing the appearance of magnification by
    >cropping the image area used of the sensor. As you might expect, this
    >reduction of the sensor area used reduces the pixel count and therefore
    >results in an image that is less sharp and more "pixelated". Most choose
    >not to use digital zoom once the results are seen (except possibly in
    >moderation, for small prints).


    Or desperation, since I can do no worse on my PC I seldom use it.


    --
    Ian G8ILZ
    Prometheus, Nov 25, 2006
    #5
  6. Ed Mullikin wrote:
    > A point of confusion: For example, what does zoom 6.7X mean? Is that
    > the multiplier if one uses the smallest to the largest image a camera
    > can record? What is the reference? A friend of mine asked me and
    > I'm not certain that I told her correctly.


    A 20 - 80mm lens and a 100 - 400 mm lens are both 4X zoom. A 20-400
    would be a 20X zoom.

    That is all it means. On a full size 35 mm or full size sensor that
    20-80 would be a nice wide to slightly long lens. On a typical 1.6 crop
    factor digital camera it would be a nice mid range zoom. The 100 - 400
    would be a nice mid range zoom on a 8x10 view camera (assuming it would
    cover the area.)

    Don't bother with any "electronic" zoom numbers. Only optical zoom
    means anything.

    --
    Joseph Meehan

    Dia 's Muire duit
    Joseph Meehan, Nov 25, 2006
    #6
  7. >A point of confusion: For example, what does zoom 6.7X mean? Is that the
    >multiplier if one uses the smallest to the largest image a camera can
    >record? What is the reference? A friend of mine asked me and I'm not
    >certain that I told her correctly.


    It's the ratio between the highest zoom and the lowest zoom. For
    example, a 35mm-105mm lens has 3x zoom. Many people mistakenly think
    that this zoom number directly represents how much closer you can get
    to a subject. It does not.

    But almost all P&S cameras start around 35mm (equiv.), so a 3x zoom
    will end up around 105mm, a 5x zoom around 150mm, etc.

    "Normal" is about 50mm (equiv.), so a 5x zoom (probably about 35mm to
    165mm) will probably bring you about 3x closer to the subject.

    -Joel

    ------------------------------------------------------------------------------
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    Dr. Joel M. Hoffman, Nov 26, 2006
    #7
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