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Thread: Noise Problems

  1. #1
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    Default Noise Problems

    I recently took a couple of shots of the same scene, altering only the shutter speed. First one is 99 sec and the second is 15 sec. WHy does the 15 sec exposure have a lot more noise than the 99 sec one? I thought that longer exposures are more prone to noise so I had thought that the 99 sec exposure would have more noise. Other than that settings were the same. Exif data intact.

    What gives? And how can I avoid noise like this?

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  2. #2
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    Did you turn off noise reduction in the second shot by any chance?

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    your exposures appear to be about the same in both shots despite a 2.5+ stop increase in shutter time value. you sure nothing else was changed?

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    I don't know what type of camera you are shooting with but it is possible it has an automatic ISO setting that is increasing your ISO to compensate for the shorter shutter speed. That is the first thing I would check. The noise definitely looks like a higher ISO.

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    That's exactly it. The 15 second shot required a higher iso to properly expose the photo (aperture remaining constant).

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    I looked at the pics with the software that came with my Canon and it says 4.0 AP for both, .33333 Compensation for both, and 400 ISO for both.

    The only difference is as noted the shutter speeds 15 and 99. Hmmm.
    Somebody gonna getta hurt real bad..

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    I shooting using a Nikon D70s and a Nikkor 50mm 1.8D lens. Full manual setting, so I know for a fact that there were no other changes to the settings as I shot the photos.

    They were shot in RAW and converted to jpg using PS CS2. As far as I know there were no preapplied settings used and the RAW preview shows the same problems.

    As canadianx noted both were shot at iso 400, no noise reduction, +1/3 EV, f4. The only changes to the settings was 15 sec -> 99 sec exposure.

    I'm lost, and I hope that my camera isn't broken.

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    Originally posted by seer_claw

    As canadianx noted both were shot at iso 400, no noise reduction, +1/3 EV, f4. The only changes to the settings was 15 sec -> 99 sec exposure.

    I'm lost, and I hope that my camera isn't broken. [/B]
    That's what the exif says for me too, but it's impossible. Changing shutter speed from 99 seconds to 15 seconds, without changing aperture or iso, would give two completely differently exposed photos. But as we can see, this two exposures are pretty much the same. iso must have changed.

    Or... the 15 second exposure was corrected in post-processing (exposure increased), which brought all the noise out.

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    Did you shoot those in RAW? If you did, it's likely your RAW conversion software automatically brightened your image to correctly expose it, thus bringing out the noise. There's no other way I can think of that a 15s and 99s would look the same - if shot in jpeg, the 15s should be significantly darker.

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    Originally posted by BerserkerCatSplat
    Did you shoot those in RAW? If you did, it's likely your RAW conversion software automatically brightened your image to correctly expose it, thus bringing out the noise. There's no other way I can think of that a 15s and 99s would look the same - if shot in jpeg, the 15s should be significantly darker.
    Ya, I did shoot these in RAW and from the looks of it PS CS2 applied some auto settings. I spent a couple of hours playing with them in PS last night to check it out.

    Its how a 15 sec exposure looks like a 99 sec exposure, with all other things being equal. I"m going to try to get the unaltered ones up they are actually a lot sharper but the 15 sec one is a lot darker.

    Thanks Guys, I appreciate the help.

    Shaun

    EDIT:

    99 sec Exposure no post processing
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    15 Sec Exposure

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    Last edited by seer_claw; 11-22-2006 at 11:08 AM.

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