Intense noise in star trails...

Discussion in 'Beyond the Basics' started by Turnerea, Oct 18, 2009.

  1. Turnerea

    Turnerea TPF Noob!

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    I've successfully done some star trail photos with seemingly no noise (or not noticeable) without going through Noise Ninja or anything. However my last time out I was a bit rushed, and had my ISO at 200 instead of 100. I didn't think it'd be a big deal... but do you think its responsible for all the noise in the image below? I also did exposures of 40 minutes instead of around 20 or so in the past. Would doubling the time, and leaving iso @ 200 really have such bad results??



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    100% crop here
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    here's an example of one of my older files (below- it's a little soft due to focusing past infinity, but no noise). I think at iso 100, but I wouldn't have though jacking to iso200 would do so much damage as to cause the noise in the images above...

    [​IMG]



    Any tips/thoughts would be appreciated.
     
  2. ErectedGryphon

    ErectedGryphon TPF Noob!

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    I have read that the longer you expose, the more noise you will have. That was in some beginners guide to astrophotography, I guess you proved it right!

    This is something I've always wanted to do, but light pollution in my area has kept me from it. Do you ever hook up to a telescope?
     
  3. BuZzZeRkEr

    BuZzZeRkEr TPF Noob!

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    Imagenomic noiseware professional will absolutely take care of that problem! It is worth every penny...and very fast :) check it out!
     
  4. Sw1tchFX

    Sw1tchFX TPF Noob!

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    How long was the exposure?

    I bet the better one was shorter.

    The thing is that ambient temperature has alot to do with it. Your sensor heats up during exposures, because of the heat, your sensor becomes noisier. Colder ambient temps, mean better noise performance.

    Shoot ISO 100, use long exposure noise reduction, and you should have some pretty ok results.

    I do alot of long exposures like that and i still get a little noise in them off my D700.
     
  5. Garbz

    Garbz No longer a newbie, moving up!

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    You're multiplying the effect on exposure time with increased sensitivity.

    A longer exposure time will produce more noise, and a higher ISO will produce more noise. So while the noise difference between ISO100 and ISO200 is very limited at short exposure durations, it becomes quite significant at longer durations.
     
  6. Turnerea

    Turnerea TPF Noob!

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    Haven't used this software, but NoiseNinja did NOTHING to the noise in these pictures.

    Yeah, the "bad" image above is 40min, while the better example is 20min. Also a difference of over 70 degrees in ambient air T...

    The temperature was higher for these latest pictures. I was in the desert as opposed to being up in the mountains, so that makes sense that you could see more noise. And combined with the ISO200 and 2x exposure time, I guess that is enough to really mess things up!! Just wanted to get some experienced eyes on the images and see if you all thought these things could add up to what I was seeing... and I guess... they can! So thanks.

    Erik
     
  7. Sw1tchFX

    Sw1tchFX TPF Noob!

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    That would do it!
     

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