What makes a fast response digital camera?

Discussion in 'Digital Cameras' started by Bryn James, May 3, 2004.

  1. Bryn James

    Bryn James Guest

    Many reviews and threads in this group draw attention to the fact a
    major feature distinguishing dSLR cameras from "pro-sumer" cameras is
    the speed of response.

    Why is this so? I can't think of any technical reason that should
    make a SLR faster to autofocus, or operate its shutter (whether
    physical or electronic) , or process/store the image than a well
    designed prosume camera could do.

    Is it all down to a marketing decision rather than any intrinsic
    design limitation of non-dSLR cameras?
    Bryn James, May 3, 2004
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  2. Point&shoot cameras have an entirely different method of using the image
    sensor as well as a smaller sensor, and the net result is poor quality
    focusing, poorer resolution and slower speed of resonse.

    When you take a picture with one of these camera, you turn it on, wait for
    the cover to open and lens to extend. You aim it at your subject compose it
    while watching the LCD image so the the shutter is all the way open to meter
    the scene and provide the live video. You press the shutter release, the
    shutter closes, the sensor is energized, the shutter opens to the metered
    aperture and for the length of time metered, then closes and the image
    exposed to the sensor is written to the storage card. Oops, the focus wasn't
    that sharp because the video nature of the chip forces it to use contrast
    detection for autofocus.

    With a dSLR, the sensor has no video function, no lens to power out. The AF
    module is faster and more accurate. When you press the shutter button, the
    shutter fires right now and the lag from shutter release to image exposure
    is 30-40 milliseconds. Time from power on to take the shot is imperceptible.
    This is opposed to the point and shoots like the Canon G5 which takes as
    much as 4 seconds to go from power-on to shot taken, has slower and less
    accurate autofocus.

    Howard McCollister, May 3, 2004
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  3. Bryn James

    Danny Boy Guest


    New here, and a strict amateur. ...as you can see ... What's a dSLR ?


    Danny Boy, May 3, 2004
  4. Bryn James

    Danny Boy Guest

    Never mind. I did a quick search and saw the prices. Bummer!! I
    guess I'll remain strictly amateur.

    Thanks anyhow.

    Danny Boy, May 3, 2004
  5. There's a fundamental technical difference in autofocus. DSLRs do
    autofocus with separate optical systems independent of the main CCD.
    This requires beamsplitters, lenses, and often several additional small
    CCD sensors, but it ultimately gives the camera an output that tells
    the camera *how far* and in *which direction8 the lens needs to move to
    focus. And it takes only milliseconds to compute this.

    In comparison, the P&S digicams use the main CCD for focus, and just
    move the main lens through a series of positions looking for best
    focus. Scanning the large main CCD takes longer than the tiny CCDs
    used in DSLRs, and a single image doesn't tell the camera anything about
    focus. The camera needs to capture multiple images as the focus motor
    is moving the lens, watching sharpness improve for a while and then
    begin to get worse, before it knows where correct focus is.

    It's cheaper but much slower.

    Dave Martindale, May 3, 2004
  6. Bryn James

    Name Guest

    a digital single lens reflex camera ... eg a Canon 300D ... same as a film
    SLR but uses a digital sensor and digital media to store the image ... well
    .... digitally!

    Name, May 3, 2004
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