Apaature and shutter speeds

Discussion in 'Digital Point & Shoot Camera' started by parkerne, Oct 25, 2007.

  1. parkerne

    parkerne Guest

    I understand, I think that the lower the F number the better. And it looks
    like the average digital camera is an f2.8.

    So, my question is, where does shutter speed come into play? And what is
    shutter lag and all that other jargon?

    What would I want in a digital P&S that is quick to take pictures (of kids
    and sports) without getting blurry pictures? Also want it ultra compact ...
    maybe compact.
     
    parkerne, Oct 25, 2007
    #1
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  2. parkerne

    Whiskers Guest

    Better for what?

    A smaller f-number indicates a larger apperture, meaning that the lens can
    let more light through; a large apperture also means that there is less
    "depth of field" so you need more accurate focussing. In practice,
    compact digital cameras usually have such a small image sensor that there
    will always be considerable depth of field, meaning that more of the image
    will be "in focus".

    Most of the time, your camera will probably be using a smaller apperture
    than the maximum it has available.

    If you have a "zoom" lens, the maximum apperture available will get
    smaller (= higher f-number) as you "zoom in".
    Fairly typical and reasonable for a compact camera.
    A higher shutter speed (= faster shutter, shorter exposure) will let light
    through for a shorter amount of time. High shutter speed is good for
    avoiding "camera shake" (where the camera moves while the shutter is open)
    and for reducing blur if the subject is moving. A longer exposure is
    useful for getting a picture if there isn't much light - provided the
    subject isn't moving and the camera is perfectly still.
    The time you have to wait between pressing the button and the camera
    actually taking the picture. This is often a significant problem with
    compact digital cameras, making them difficult or impossible to use for
    "action" shots.
    There are books full of answers to that question ;))
    Kids: look for cameras with "image stabilisation" and good flash. Things
    like "face recognition" and "portrait mode" might be worth having.

    Sport: image stabilisation is useful here too - and you *must* be able to
    turn the flash off so as not to disturb the other spectators or the people
    taking part (you might be thrown out of the event for using flash, in some
    places). An eye-level optical viewfinder can be a godsend for any outdoor
    photography, but few compact digital cameras have them these days - and
    the LCD 'screen' is not always going to be useable in daylight, no matter
    what the advertising claims.

    Don't expect any digital compact or ultra-compact to be particularly good
    for sport photography; but they can be very effective for family-album
    snapshots. Get to know the camera well before you try using it for
    anything important.
     
    Whiskers, Oct 25, 2007
    #2
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  3. parkerne

    parkerne Guest

    Smaller F number better for portrait pictures, to make the background
    slightly softer and the person more in focus, also reducing the depth of
    field... correct?

    And getting a camera with a fast shutter speed will be better so my pictures
    won't be as much as a blur when my kids are moving around? That and one with
    IS. 1/2000s decent or are the better in a P&S?

    What can you or anyone else tell me about the Nikon S510, P50, P5000 or the
    Canon A720 IS... those are what I have been looking into, but can't seem to
    figure out which one will be the best for me.

    Pictures of:
    Kids, kids playing sports, every day activities.
    I do want at least an 8 MP, I do on occasion make my pictures bigger than the
    regular 8x10.
    Movie mode - I love using it now.

    They have one that is a S51, but it's a f3.3 which someone told me wasn't
    good, and that I wanted one that was at least as low as a f2.8 - which is why
    I asked. But I like that the others have better optical zoom, not much, but
    still, more, and I know the Canon has a lot more, but just not sure about it.
     
    parkerne, Oct 25, 2007
    #3
  4. parkerne

    Whiskers Guest

    You won't get very much of an effect like that with a point-and-shoot
    compact digital camera; the image sensor is too small. Simple 'auto-focus'
    and 'auto-exposure' makes it something you can't easily control anyway.
    But some cameras have a 'special effect' to artificially blur most of the
    background in 'portrait mode' - and of course, image processing software
    can do that (takes practice!).
    You an only use a fast shutter speed if there is enough light. Most
    digicams let you change the sensitivity of the image detector (higher ISO
    number = greater sensitivity which makes a higher shutter speed possible)
    but there is a trade off in image quality with greater sensitivity.
    I doubt if you'd notice any difference in practice between point-and-shoot
    cameras with maximum appertures of f/3.3 and f/2.8. Other factors, such
    as the image sensor used, the quality of the lens, and the design of the
    electronics and software inside the camera, are more important.

    Try looking at <http://www.steves-digicams.com/> and
    <http://www.dpreview.com/> for information and reviews of particular
    cameras.
     
    Whiskers, Oct 25, 2007
    #4
  5. Correct with larger cameras, but very small cameras have so much depth of
    field you usually won't be able to reduce it much.
    Image stabilization is always good to have. I wouldn't worry too much about
    shutter speed in a small camera. You would seldom if ever need 1/2000 in
    such a camera and might not be able to use it anyway unless the light was
    very bright. Higher shutter speeds = less light passing through the lens,
    and you need a certain amount of light to get a good picture.
    The S510 is very flat and pocketable, if that's important to you. It has a
    nice large LCD monitor but no optical viewfinder, which may or may not be
    important to you. Personally I find *all* LCD screens hard to read in bright
    sunlight and for that reason prefer a camera which also has an optical
    viewfinder. But apparently some people don't mind the absence of a
    viewfinder.

    The P50, P5000 and P5100 have optical viewfinders as well as a large LCD
    monitor. I like them better for that reason, and also the fact that they
    have more user controls and should be more capable cameras generally. The
    P50 also has better wide angle capability than the others mentioned, and
    should be attractively priced. But it doesn't have real optical image
    stabilization -- it has *electronic* stabilization which is not as
    effective.

    The P5000/P5100 are the most advanced Coolpix models available today and
    priced accordingly. They both have real optical stabilization which is good.
    If you're a beginner they probably have more features than you need -- you
    may or may not "grow into" such a camera.
    Not necessarily. In ordinary use you probably would not notice the
    difference between a camera with f/3.3 and one with f/2.8, and also keep in
    mind that these f-numbers only apply to the lens at the *short* end of the
    zoom range -- at the long end, the f-number is invariably higher ( = smaller
    relative aperture) in this type of camera, and the long end is where you'd
    really prefer to have a larger aperture. Many compact/ultracompact cameras
    are f/5 or so at the long end.

    A longer zoom is nice dependng on circumstances, but may not be very useful
    if the aperture at the long end is very small, since the longer the zoom the
    more it magnifies camera shake -- so to avoid blurring the picture you will
    need a higher shutter speed, and if the aperture is small there may not be
    enough light for the camera to set a higher shutter speed. Generally
    speaking, if you need a pocketable camera I would advise not being too
    ambitious about zoom ratio. If you really want a camera with a long zoom
    range I'd suggest looking into one of the several "superzoom" models on the
    market -- but none of them are really pocketable. So that's the trade-off.

    Neil
     
    Neil Harrington, Dec 15, 2007
    #5
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