Optical Zoom vs Megapixels

Discussion in 'Digital Photography' started by Johnny, Sep 8, 2005.

  1. Johnny

    Johnny Guest

    Hi all,

    I currently have an Olympus C-2100 Ultra Zoom (10X optical), but it
    only has 2 megapixels. I'm in the market for a new camera, but I was
    wondering if anyone knew of a calculation that I can compare optical
    zoom & megapixels (understanding that digital zoom is worthless for my
    purposes) when they are apples and oranges.

    For example: When both are at max zoom*, is a 4 megapixel 1x zoom the
    same as a 1 megapixel 2x zoom because of the inverse square law of
    physics? I mean, if I zoom* in on a tree in the far distance so it
    takes up less than 1/10th of the screen, will the resulting number of
    pixels for each tree image be the same for the 1x 4MP and the 2x 1MP?

    If that's true, then I'd need a 8 megapixel, 5X optical zoom camera to
    replace my Olympus when using max zoom. I understand that the larger
    megapixel will completely win out all other times.

    * = Yes, yes, I know a 1x zoom can't zoom. I tried to keep the math
    Johnny, Sep 8, 2005
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  2. Johnny

    Nostrobino Guest

    That depends on the focal lengths used, not just the zoom ratio. For
    example, my Nikon 8400 has a 24-85mm zoom and my Canon S60 has a 28-100mm
    zoom (35mm equivalencies, of course). The zoom ratio is almost identical for
    both, a bit over 3.5x, but the two cameras produce different degrees of
    magnification at either end of the zoom range. Another camera might have,
    say, a range of 38-135mm and that would still be about the same zoom ratio
    but with still different results in terms of image magnification (or pixels
    for any given subject and distance, if you want to put it that way).

    I'm not sure I understand the premise behind your question, but I suspect
    you are making some sort of invalid assumption.

    Not necessarily. All pixels are not created equal. Many 8-megapixel cameras
    have different sizes of sensor, and the general rule is that the larger
    sensor produces the better (lower noise) image for any given megapixel size.

    Why not just say FFL (fixed focal length) instead of "1x zoom," since the
    latter phrase is thoroughly self-contradictory.

    Nostrobino, Sep 9, 2005
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  3. Johnny

    Terry Guest

    You are thinking correctly, mostly. You just need to realize that it's
    the focal length, not the X factor. Your 2100 is 38 to 380 (35 mm
    equivalent), as I recall. So you'd need an 8 megapixel camera with a
    tele focal length of 190 mm. You might get that in a 38-190 5x lens,
    or a 27-190 7X lens, etc.

    Terry, Sep 9, 2005
  4. Johnny

    Stewy Guest

    Well, the 2100's zoom is 38-380 (35mm equiv) meaning it's around 0.75x -
    7.5x. The Panasonic FZ5 is 5 megapixels with a 36-432mm zoom (0.75x -
    almost 9x).

    Now, whether the Panasonic has a better lens than the Olympus is
    anyone's guess or that the body is harder wearing. Is image
    stabilization worthwhile?

    Try http://www.dpreview.com/ and see what elements of camera design are
    important to you and make a short list - you'll find some discrimination
    working here on this newsgroup - you find some people swearing by a
    certain camera and some people swearing at the same camera.
    Then there are the REAL camera people paying top dollar for huge chunks
    of hardware to hang around their necks but not actually doing much
    Stewy, Sep 9, 2005
  5. Johnny

    wavelength Guest

    Just to start, I'm assuming in my answers that you are *NOT* talking
    about digital "zoom" which is cropping in camera.
    No. Does film lose 3/4 of it's emulsion suddenly because you zoom?
    No again.
    Photons are much smaller than anything a current chip fab can make to
    capture them at the pixel level. For each pixel sensor on the CCD or
    CMOS chip, i'd wager there are hundred of photons hitting it. Altering
    the path of the light doesn't change that fact. When we get to
    terapixel camera's on 24x35mm sensor, one might have to worry about
    what you are speaking of.

    Get an 8mp, Sony just announced 10mp camera, you'll be outdated in a
    year if you go lower at this point. :0) Just kidding. A 5mp 10-12x zoom
    should keep you happy for years to come. And you'll finally be able to
    print 8x10's
    wavelength, Sep 9, 2005
  6. Stewy wrote:

    David J Taylor, Sep 9, 2005
  7. Johnny

    Rich Guest

    The basic premise is simple; If you have a camera that you are forced
    to crop images heavily with, cutting down an 8 meg image to 4 meg or
    less, a camera with less megapixels and a longer zoom can beat it for
    image resolution. For instance, an 8 meg image that is cropped by 15%
    is a 6 meg image. If cropped by 25% per side, the final image is only
    4 meg.
    Rich, Sep 9, 2005
  8. Johnny

    SteveB Guest

    I would have thought he was well aware of the pros and cons of image
    stabilisation having had a few years using it.
    SteveB, Sep 10, 2005
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