newb - tell me about ISO

Discussion in 'Digital Photography' started by erik527@gmail.com, Mar 29, 2006.

  1. Guest

    I have a Canon SD550 which lets me adjust the ISO when using the manual
    settings. I understand that a higher ISO leads to more detail in the
    photo but can also lead to more 'noise' in the image.

    Under what conditions would i set this higher or lower? Are there any
    general rules about ISO settings? I think my camera goes from 50 to
    400. Thanks!
     
    , Mar 29, 2006
    #1
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  2. Jem Raid Guest

    <> wrote in message
    news:...
    >I have a Canon SD550 which lets me adjust the ISO when using the manual
    > settings. I understand that a higher ISO leads to more detail in the
    > photo but can also lead to more 'noise' in the image.

    Lower ISO more detail.
    Higher ISO more noise less detail.

    > Under what conditions would i set this higher or lower? Are there any
    > general rules about ISO settings? I think my camera goes from 50 to
    > 400. Thanks!

    If you need to stop something going fast in low light use a high ISO, try it
    it the camera you will see the shutter speed rise with the ISO, do the
    reverse to blur a moving object.

    Try it at various settings and make your own choice as to which sort of
    images suit which speed.

    It is not necessary to do what everyone else tells you to.

    Jem

    -------------------------------------
    Birmingham Independent Photographers
    http://bip.wikispaces.com/
     
    Jem Raid, Mar 29, 2006
    #2
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  3. Helen Guest

    <> wrote in message
    news:...
    > settings. I understand that a higher ISO leads to more detail in the
    > photo but can also lead to more 'noise' in the image.
    >


    Less detail actually; the noise obscures the fine detail.
     
    Helen, Mar 29, 2006
    #3
  4. al-Farrob Guest

    wrote:
    > I have a Canon SD550 which lets me adjust the ISO when using the manual
    > settings. I understand that a higher ISO leads to more detail in the
    > photo but can also lead to more 'noise' in the image.
    >
    > Under what conditions would i set this higher or lower? Are there any
    > general rules about ISO settings? I think my camera goes from 50 to
    > 400. Thanks!


    You can look at ISO as a measure of sensitivity.
    Named ISO because it refers to a standard. (ISO stand for International
    Standards Organization).

    With digital, and simplifying, a higher ISO is accomplished amplifying
    the signal of the sensor, so you can with less light or less time
    achieve the same signal.
    Of course, when you amplify a sensor signal, you also amplify the
    noise.
    This is only a simplifying way to put things.


    al-Farrob
    http://www.al-farrob.com
    new photos every week
     
    al-Farrob, Mar 29, 2006
    #4
  5. Bill Funk Guest

    On 29 Mar 2006 11:30:14 -0800, "" <>
    wrote:

    >I have a Canon SD550 which lets me adjust the ISO when using the manual
    >settings. I understand that a higher ISO leads to more detail in the
    >photo but can also lead to more 'noise' in the image.
    >
    >Under what conditions would i set this higher or lower? Are there any
    >general rules about ISO settings? I think my camera goes from 50 to
    >400. Thanks!


    Al-Farrob has it pretty right.
    Higher (or lower) ISO doesn't equal more detail.
    Higher ISO does mean more noise, which can hide detail.
    The ISO rating is a measure of the sensitivity of the sensor (digital
    or film). A higher ISO means the sensor needs less light to make a
    properly exposed image; it also means more amplification is used,
    which increases noise.
    You might use a higher ISO if a lower one would mean too long an
    exposure. Upping the ISO will let you use a faster shutter speed for
    the same exposure; it will also let you use a smaller aperture to gain
    depth of field. But this also means more noise.

    You've already bought the camera, so taking pictures is virtually
    free. Take lots, and experiment. Your idea of what's "good" will
    differ from others'. So take lots of pics, and learn from the results.
    --
    Bill Funk
    replace "g" with "a"
     
    Bill Funk, Mar 29, 2006
    #5
  6. J. Clarke Guest

    wrote:

    > I have a Canon SD550 which lets me adjust the ISO when using the manual
    > settings. I understand that a higher ISO leads to more detail in the
    > photo but can also lead to more 'noise' in the image.
    >
    > Under what conditions would i set this higher or lower? Are there any
    > general rules about ISO settings? I think my camera goes from 50 to
    > 400. Thanks!


    Don't know where you got the idea that higher ISO "leads to more detail".
    ISO is the digital equivalent of film speed with film, if that means
    anything to you. It is a measure of sensitivity--the higher the ISO the
    greater the sensitivity but you pay for that increase with increased noise
    in digital cameras or grain in film cameras.

    There's a relationship between aperture, shutter speed, and ISO. If you
    hold the ISO constant and change the aperture one stop the shutter speed
    has to be slowed by a factor of two, so for example if you're able to shoot
    at f/4 and 1/250 with ISO 200, then changing the shutter speed to 1/500
    would require that you either change the aperture to f/2.8 (the aperture
    numbers are not linear--there's an explanation at
    <http://www.uscoles.com/fstop.htm>) or change the ISO to 400. Similarly if
    you change the ISO to 400 then you'd have to either change the shutter
    speed to 1/500 or the aperture to f/5.6. Or if you change the aperture to
    f/2.8 then you'd have to either change the shutter speed to 1/500 or the
    ISO to 100.

    As a general rule you want to use the lowest ISO that will give you the
    shot. Not something to agonize over though--go out and shoot at different
    ISO values and examine the result and pretty soon you'll get used to using
    it.

    --
    --John
    to email, dial "usenet" and validate
    (was jclarke at eye bee em dot net)
     
    J. Clarke, Mar 29, 2006
    #6
  7. Bill Funk wrote:

    > The ISO rating is a measure of the sensitivity of the sensor (digital
    > or film). A higher ISO means the sensor needs less light to make a
    > properly exposed image; it also means more amplification is used,
    > which increases noise.


    I think what is really happening is that the sensor sensitivity can't
    really change, all you are doing is exposing further down into the
    blacks. Then you can amplify that signal to get the values back up to
    respectability, but a lot of amplification gives more noise. If I'm
    wrong about this, I will eat my sensor, but it's a good description of
    the result.

    Gary Eickmeier
     
    Gary Eickmeier, Mar 30, 2006
    #7
  8. Guest

    50 is less sensitive to light. you need to expose the image for longer.
    but you get the best quality image. Also you will need a longer
    exposure time which means more possibility of camera shake. Also larger
    aperture to capture as much light as possible which equals less depth
    of field. Generally you will need a tripod to be able to have a longer
    exposure with less chance of camera shake or a smaller aperture for
    more depth of field or both. And the longer exposure means the subject
    will have to be still.

    100 is twice the sensitivity of 50. It will allow for a shorter
    exposure (less camera shake) or a smaller aperture (more depth of
    field).

    200 is twice the sensitivity of 100 and 4 times the sensitivity of 50.

    400 is twice the sensitivity of 200 and 8 times the sensitivity of 50.

    But the higher the iso, the more applification of the signal, and the
    more possibility of noise.

    150 to 200 ISO is good for general shots, outdoors in moderate shade.
    You should be able to get F5.6 to F8, for good depth of field, at 1/60
    exposure, for no hand-held camera shake.

    Higher ISO also allows for faster shutter speeds to capture or freeze
    movement. Slower shutter speeds will allow moving objects to blur,
    desired or not.

    In bright light, or with a tripod, with slow moving or stationary
    objects, you can use less ISO. In darker conditions, or to capture
    movement with faster shutter speeds, or with a long lens, use higher
    ISO.

    TC

    wrote:
    > I have a Canon SD550 which lets me adjust the ISO when using the manual
    > settings. I understand that a higher ISO leads to more detail in the
    > photo but can also lead to more 'noise' in the image.
    >
    > Under what conditions would i set this higher or lower? Are there any
    > general rules about ISO settings? I think my camera goes from 50 to
    > 400. Thanks!
     
    , Mar 30, 2006
    #8
  9. Marvin Guest

    Jem Raid wrote:
    > <> wrote in message
    > news:...
    >
    >>I have a Canon SD550 which lets me adjust the ISO when using the manual
    >>settings. I understand that a higher ISO leads to more detail in the
    >>photo but can also lead to more 'noise' in the image.

    >
    > Lower ISO more detail.
    > Higher ISO more noise less detail.

    Noise does not necessarily obscure detail, unless the
    signal-to-noise ratio is quite low. The main factor in
    detail (i.e. resolution) is the number of pixels.
    >
    >
    >>Under what conditions would i set this higher or lower? Are there any
    >>general rules about ISO settings? I think my camera goes from 50 to
    >>400. Thanks!

    >
    > If you need to stop something going fast in low light use a high ISO, try it
    > it the camera you will see the shutter speed rise with the ISO, do the
    > reverse to blur a moving object.
    >
    > Try it at various settings and make your own choice as to which sort of
    > images suit which speed.
    >
    > It is not necessary to do what everyone else tells you to.
    >
    > Jem
    >
    > -------------------------------------
    > Birmingham Independent Photographers
    > http://bip.wikispaces.com/
    >
    >
     
    Marvin, Mar 30, 2006
    #9
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