D70s Noise Problem

Discussion in 'Beyond the Basics' started by Anubis, May 31, 2009.

  1. Anubis

    Anubis TPF Noob!

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    Hi,

    Can anyone explain why I get noise in the second image please. I've noticed this happening on a lot of my photos lately. Both taken with the following settings; ISO250, f4.5, and 70mm focal lenth. The first image was 1/250 sec and the second image was 1/640 sec. I have another shot the same as the second taken at 1/125 sec with just as much noise. Both shot in RAW.

    [​IMG]


    [​IMG]

    If anybody could shed some light on the cause it would be much appreciated!

    Cheers,

    A.
     
  2. Pure

    Pure TPF Noob!

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    You may want to check your statement again. There is no way that the second picture is ISO250 f4.5 1/640.

    Assuming you took these two pictures within a few minutes of each other, then the second picture should be really dark, underexposed, compared to the first.


    Despite that, it is extremely clear that the second picture looks noisey due to using a high ISO to capture the picture. Higher ISO typically means more noise.


    Check your EXIF data, and you will find you shot the second at something like ISO 1250 f/4.5 1/640 assuming exposures were exposed dead center.

    1/125 to 1/640 is 2 and 1/3 stops, so applying that to ISO 250, you get ISO 1250.
     
  3. Anubis

    Anubis TPF Noob!

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    Thanks for the reply, but that is the exif info ...I shoot on full manual so it shouldn't have changed by itself.
     
  4. manaheim

    manaheim Jedi Bunnywabbit Staff Member Supporting Member

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    I haven't seen a case where the exif has lied before... that would be odd.

    And I can't really see any other reason why the image would look that noisy. Maybe a HAIR underexposed, but that noise is kinda extreme.

    D70 is an old old camera now... maybe it just wigged out on one shot?
     
  5. Anubis

    Anubis TPF Noob!

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    I've done a bit more reading and it does seem to be an issue caused by underexposing. I might start bracketing in future, I was just messing around yesterday but I'd hate to lose a good shot because it was a little underexposed.

    Thanks for the replies! :)
     
  6. Dwig

    Dwig TPF Noob!

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    ...making the second shot 1 1/3 stops underexposed relative to the first. Adjusting such a shot to get similar tonal reprouction will expande the shadow information making the noise more significant. Its just like shooting at higher ISOs except that there is a tendency to increase the local contrast in the shadows more making the noise even more pronounced.
     
  7. gsgary

    gsgary Been spending a lot of time on here!

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    I have the classic 1D Canon, if i over expose a touch i get less noise
     
  8. JerryPH

    JerryPH No longer a newbie, moving up!

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    I just tried 2 different EXIF viewer programs and though I know the camera, lens used , program used to create/modify the file (Elements 5), and create date and some more useless info... basic info like ISO, shutter and what not are not shown using Opanda and Kuso EXIF viewers.

    Strange.
     
  9. Garbz

    Garbz No longer a newbie, moving up!

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    Full manual implies controlling both the shutter speed and aperture. If your camera is set to AUTOISO then it would adjust the ISO to centre the exposure even if you shoot on full manual. At least that's how it happens on the D200 and D40.

    Both of those photos look like they were exposed equally. Did you push one in photoshop? If not then it's not underexposed. Which is what leads to user error. There's no way that that image is on the same ISO as people already have said the exposure value is quite different. 2.3stops lower on the second one. So it should definitely not be darker.

    You also get less dynamic range when you adjust the exposure afterwards. This is not the right solution to the problem.
     
  10. Anubis

    Anubis TPF Noob!

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    By full manual I mean I control the settings for shutter, aperture, ISO, white balance and focus. The only thing I did to the images was to export them from RAW to JPEG in Elements 5. They are absolutely both shot at the same ISO. The only difference is the shutter speed. I wonder if the camera is trying to adjust the exposure itself after the shot is taken? (Nikon D70s)
     
  11. gsgary

    gsgary Been spending a lot of time on here!

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    Well that means the second shot was under exposed if you didn't adjust the aperture, what do you expect if you under expose this test is a total waste of time
     
  12. Anubis

    Anubis TPF Noob!

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    What I would expect from an under exposure would be a dark image, not the grain that appeared. As stated originally, I did not know the source of the grain. I wouldn't say it was a waste of my time since now I have an answer.
     

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