Canon ISO Speeds in Different Mode Settings

Discussion in 'Digital Photography' started by Daboo1, Jul 21, 2006.

  1. Daboo1

    Daboo1 Guest

    I just purchased a Canon PowerShot S2 after owning a couple Olympus
    super-zoom cameras. I suspect my question is generic though to any
    Canon model. What I am finding frustrating, is not being able to tell
    what the ISO speed a particular picture was taken at.

    It seems that if I am manually controlling the shot, the ISO speed is
    available, but if I am using any of the other special mode settings,
    like Indoor, Fireworks, Scenery, Action, etc., then all I know is that
    the picture was taken using that mode.

    So is there any way to tell what the ISO speed was for a picture taken
    using one of those modes?

    One of the reasons I'm concerned about this, is that camera reviews
    stated that the noise level went up considerably above ISO 100. So I'm
    wondering how many of those modes are using a higher ISO setting.

    Thank you in advance.
    Chris
     
    Daboo1, Jul 21, 2006
    #1
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  2. Daboo1

    SleeperMan Guest

    you're right...that's common to all canon's... generally, most shots are
    taken with iso around 100, but i always have ISO set to either 50 or 100
    manually. Just have wheel set to P and then depending on light conditions,
    set iso to 50 or 100, in some cases 200. I also use NeatImage program with
    succeess to remove noise quite decently from hi-iso shots. take a look on
    these two shots, taken at ISO400 (first one is 3.5M, second, filtered is
    2M).

    http://www.protoncek.com/misc/test1.jpg original
    http://www.protoncek.com/misc/test2.jpg filtered
    other settings were: 1/25 sec, F3.2
     
    SleeperMan, Jul 22, 2006
    #2
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  3. Daboo1

    Shawn Hirn Guest

    Any decent photo editing program should provide a way to display that
    information.
     
    Shawn Hirn, Jul 22, 2006
    #3
  4. Daboo1

    SleeperMan Guest

    if shot is taken in auto mode, there's no decent, undecent or profi program
    that will tell you this since it's not written in exif data...
     
    SleeperMan, Jul 22, 2006
    #4
  5. Daboo1

    Dave Guest

    Not sure on your model but on my Canon 620 the histogram view (image
    review) tells the ISO of each shot. Hope this helps.

    Dave
     
    Dave, Jul 23, 2006
    #5
  6. Daboo1

    SleeperMan Guest


    just tried...shows when in P mode and ISO set manually, but not in auto mode
    of any kind. Same was in S1...it's really odd, why should canon fear to show
    auto iso setting..
     
    SleeperMan, Jul 23, 2006
    #6
  7. One possibility: the processing done in "auto ISO" doesn't correspond
    exactly to what you'd get from manually setting the ISO.

    For example, suppose that the ISO setting simply sets the analog
    amplifier gain in the camera to match the expected CCD output signal
    dynamic range to the A/D converter range. Also suppose that the
    camera's minimum ISO setting is 50. In "auto", the camera may always
    try to expose at ISO 50 to get the cleanest images, but if the image
    ends up too dark (e.g. a flash shot beyond the flash range) the camera
    performs the equivalent of a "Levels" adjustment to fill the histogram
    and make the image appear properly exposed.

    This adjustment is *not* the same as selecting a higher ISO in the
    first place, because adjusting the digital values after A/D conversion
    is not as good as adjusting the voltage before the A/D. But it gives
    a better-exposed image, which is the point.

    I don't know what *really* goes on inside Canon cameras, but this is a
    guess. In my own limited tests, it seems that Auto ISO always exposes
    the same as ISO 50 in non-flash situations, but I have seen the
    automatic adjustment effect described above in flash images.

    Dave
     
    Dave Martindale, Jul 23, 2006
    #7
  8. Daboo1

    SleeperMan Guest

    i never went that far into investigation, but i agree that it is a
    possibility, sure. But, in my case, i always use manual setting of 50 if
    possible, so i always know where i stand...
     
    SleeperMan, Jul 23, 2006
    #8
  9. I tend to set a manual ISO myself on the Canon cameras that have
    P/Tv/Av/M modes, because they will tell me what aperture and shutter
    speed they're going to use (even in full-auto-exposure P mode) and I can
    decide whether I want to trade off ISO for a faster shutter or smaller
    aperture.

    I'm not sure what to do about my S410, though. Its "Manual" mode is
    actually about the same as P mode on the other camera (still auto
    exposure), but it doesn't tell me what shutter speed or aperture it's
    going to use. Lacking that information, I sometimes leave the camera in
    Auto ISO unless it's really obvious that an ISO greater than 100 is
    warranted.

    Dave
     
    Dave Martindale, Jul 24, 2006
    #9
  10. Daboo1

    SleeperMan Guest

    on S2 P mode is in fact auto mode but with all settings changeable, while
    when in auto, you can't change anything. But, S2 shows you shutter speed and
    aperture in any case, no matter where dialer is, while ISO is not displayed
    in any case except if set manually, sure. If you don't have those info, then
    can be confusing at times, i admit... :-(
     
    SleeperMan, Jul 25, 2006
    #10
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