Reducing noise in long exposures?

Discussion in 'Beyond the Basics' started by Restomage, Mar 30, 2010.

  1. Restomage

    Restomage No longer a newbie, moving up!

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    I got a shutter release cable for my D90 to do some long exposures at night during the stars. Since i'm shooting with a crop frame camera, it's obviously a lot more prone to noise. I did a 5 minute exposure the other night and even at ISO 200 I got a bunch of noise. Are there any other tips for reducing noise? There was a little ambient light from the city behind me which could have made the grain show up more than it normally would have but if anyone has any reccomendations let me know.
     
    Last edited: Mar 30, 2010
  2. Sw1tchFX

    Sw1tchFX TPF Noob!

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    is it the purple amp noise in the corners? that's normal.


    you need to have long exposure noise reduction on. it uses a dark frame to subtract the noise, but at the cost of detail.
     
  3. KmH

    KmH Helping photographers learn to fish Supporting Member

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    Grain and noise are not the same thing. Electronic noise is random.

    Noise (electronics) - Wikipedia, the free encyclopedia
     
  4. astrostu

    astrostu I shoot for the stars

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    Define "noise" here. Or, better yet, post a full-size crop portion of the image showing your issue.
     
  5. Restomage

    Restomage No longer a newbie, moving up!

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    Here is the noise I'm talking about:

    [​IMG]
     
  6. Tiny

    Tiny TPF Noob!

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    shoot at a higher F-stop, ISO 100, and a longer exposure. 5 min is not very long for a star trail.
     
  7. Restomage

    Restomage No longer a newbie, moving up!

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    I know it's not very long for a star trail but that exposure was only about 5 min and look how much noise I got. That's my issue.
     
  8. Garbz

    Garbz No longer a newbie, moving up!

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    There's a trick to this.

    Image stacking. Noise is the best friend of the astro photographer. It allows you to extract extra detail that your camera may not have recorded (sounds crazy but it is statistically very clever).

    What you want to do is get a program like Image Stacker and then do maybe 10 30second images. For the final image use the "add" function. Each new image will bring about a new amount of statistically random noise. Therefore when you stack 10 30 second images together you actually average the noise out of the image.
     
  9. Sw1tchFX

    Sw1tchFX TPF Noob!

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    This isn't an almost 100% crop is it?

    I looked at the EXIF and your exposure was 151 seconds, just over 2 minutes.

    At ISO 200, you shouldn't be getting that much noise at 2 minutes. was it a warm night?

    I have a friend with a D300 and he doesn't get that kind of noise even when he's doing exposures that are in the realm of 10 minutes.

    I'd try it again, find a subject that can meter out 5 minutes at ISO 100, and see what happens.
     
  10. KmH

    KmH Helping photographers learn to fish Supporting Member

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    I'd take it out of Matrix metering and I would also pick something other than Auto white balance.

    Did you turn on Long Exposure Noise Reduction in the camera menus?

    As pointed out 151.9 seconds is only half way to 5 minutes (300 seconds).

    Looks like you had a bit of wind too.
     
  11. Brick

    Brick TPF Noob!

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    I've yet to take a long exposure with my d90 and not have to deal with at least a little bit of noise. Maybe we're both doing something wrong. Anyway, I use noise reduction software. Some of the most popular are noiseninja and noiseware. Topaz deNoise has a fully functional free 30 day trail you could give a shot. They do kill some details but unless you're looking at the full size image it's not bad.
     
  12. the iconic image

    the iconic image TPF Noob!

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    Before you go out and buy any noise reduction software, CS4 has (if you learn how to use it in advance mode) a very adequate in most cases, noise reduction program built in. I suggest you learn it, try it, and see if it doesn't work for you. As with ALL noise reduction software, you are going to lose some detail. Works better on some images than others obviously.

    mike zukerman photography

    the Iconic Image
     

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