Why is this picture noisy?

Discussion in 'Critique Forum Archives' started by kweinert, Feb 16, 2007.

  1. kweinert

    kweinert TPF Noob!

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    I took this last December with my older camera. It was a bright, shiny day and I liked the result, except that there is so much noise in it.
    [​IMG]

    The full-sized image can be seen at http://weinertfamily.org/IMG_0854.JPG

    Here's the data for the original image:

    File size : 3485273 bytes
    Camera model : Canon PowerShot S2 IS
    Date/Time : 2006:12:10 14:09:46
    Resolution : 2592 x 1944
    Flash used : No
    Focal length : 39.1mm (35mm equivalent: 246mm)
    CCD width : 5.72mm
    Exposure time: 0.0005 s (1/2000)
    Aperture : f/5.6
    ISO equiv. : 400
    Exposure bias: -1.00
    Whitebalance : Manual
    Metering Mode: matrix

    Is it because the ISO was set too high?

    I'm pretty new to photography - while we had to spend money on film my wife took all the pictures since she has/had a better eye than I do. I end up deleting a lot of images, but I am getting better.

    Thanks for any feedback on this one.
     
  2. Peacemaker636

    Peacemaker636 TPF Noob!

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    Probably because the ISO is at 400. Also, the fact that the camera's a p&s means it'll have a smaller sensor, which equals higher noise factors.
     
  3. benjyman345

    benjyman345 TPF Noob!

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    Yes ISO would be the main problem. ISO 400 is not necessary during a bright sunny day.

    ISO 100 or even less should be suitable for bright outdoor lighting. At dawn and dusk you would probably use ISO 200 +
    and 400 for dark, indoors etc etc..
     
  4. kweinert

    kweinert TPF Noob!

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    I'll just note here that it says ISO equiv - I don't believe I had the ISO set, most likely it was on auto.

    I'll not dispute that there's a lot of truth to this. However, I'd be interested in *why* it's so much different than this one, taken about 90 seconds earlier:

    [​IMG]

    (full size at
    http://weinertfamily.org/IMG_0852.JPG)

    The EXIF info on this one is:

    File date : 2007:01:02 19:43:37
    Camera model : Canon PowerShot S2 IS
    Date/Time : 2006:12:10 14:08:19
    Resolution : 2592 x 1944
    Flash used : No
    Focal length : 39.1mm (35mm equivalent: 246mm)
    CCD width : 5.72mm
    Exposure time: 0.0040 s (1/250)
    Aperture : f/4.0
    Whitebalance : Auto

    A couple of things are obviously different:

    1. No ISO information, not sure why that is
    2. Longer exposure
    3. smaller aperature (more light, right?)

    I'm not sure why that results in a better picture.

    Thanks again for commenting.

    Oh, I had the S2 IS because it was an entry into the field that is a bit more than point and shoot. Definitely not an SLR, but it does give some of the manual capabilities. Basically a stepping stone from p/s cameras into at least entry level DSLR.

    I am now learning to use a Canon 350D which is why I'm trying to understand what went wrong so when I get this result I have an idea what to do to correct it for the next shot.
     
  5. benjyman345

    benjyman345 TPF Noob!

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    I would assume that the photo with less noise was because the camera automatically selected a smaller ISO setting... Did you have the camera set to Auto???

    Also the noisy image was set to -1.0 exposure bias.

    The Exif data says that you set the camera to Auto Bracket and it probably has chosen a higher ISO setting to achieve a different exposure... I.E less light or more light sensitive.
    I would suggest that you set your ISO setting manually to 100 or less when taking a photo in bright sunlight if your camera is producing noisy images and that should solve the problem.
    The longer exposure would suggest why the camera selected a higher ISO setting such as 400 so that the photo was not underexposed. The shutter speed does not need to be 1/2000 second. This is only to freeze fast moving action or in super bright light when the aperture is closed right down and it is still to bright.
    I hope that helps...

    P.S - The fact it does not list the ISO setting on one photo seems to suggest it was probably taken on a different camera setting but I am not sure about that???
     
  6. kweinert

    kweinert TPF Noob!

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    Some aspects, yes. The ISO was probably on Auto.

    Yes, I was bracketing as a way of comparing images with different exposures to try and see what makes a good picture, what I would want to change manually to get the result I want when an image turns out not as I'd like it.

    Again, auto-bracketing on purpose as a way of getting "the same" image with different parameters and comparing them.

    It does, it does. Thanks for your feedback.
     
  7. Peacemaker636

    Peacemaker636 TPF Noob!

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    The second picture is less noisy because the aperture was wider. Probably because you were zoomed in on the first one, or something of that nature.

    When the aperture is wider, more light gets in, which means that it doesn't need to be as sensitive. Lower sensitivity=less noise.
     
  8. Digital Matt

    Digital Matt alter ego: Analog Matt

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    In this case, opening the aperture is not really what's needed. There is already more than enough light. The first shot was taken at ISO 400, and 1/2000 /sec, f/5.6. An equivalent exposure could have been ISO 100, 1/500, f/5.6. Much less noise. I would have even opted for ISO 100, 1/250, f/8.
     
  9. kweinert

    kweinert TPF Noob!

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    Thanks to all for your replies. I'll let this one rest now as it's the older camera that I'm moving away from. I will note once again that in this case the camera chose the ISO 400 in the first image. I'm not sure why it did that, but it doesn't really matter now.

    The information about equivalent exposures is useful. I'll bring out the newer camera (Canon 350D) and take some pictures with the equivalent exposures to try and stick the comparisons in my mind.

    Again, thanks for the help. Very nice to get some good (and polite!) replies.
     
  10. elsaspet

    elsaspet TPF Noob!

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    First of all, I don't notice the noise, and secondly, noise is NOT a bad thing as long as it's monocromatic. I actually add it into most photos.
     

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