A&P noise in my picture

Discussion in 'Lifestyle' started by Deepsix, Jan 31, 2009.

  1. Deepsix

    Deepsix OT Supporter

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    maybe this is a stupid question, but i took this pic at iso 100 with an 8 minute exposure. did the long exposure cause the noise despite the low iso? exif data is there.

    jpeg compression was a bitch and it isn't this crummy normally. the horizontal lines are what i'm wondering about.

    [​IMG]
     
  2. DRAIGON

    DRAIGON New Member

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    star trails?
     
  3. DRAIGON

    DRAIGON New Member

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    I see it now. Not sure
     
  4. OneTwo

    OneTwo me>you OT Supporter

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    looks more like compression and banding then noise.
     
  5. Deepsix

    Deepsix OT Supporter

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    Last edited: Jan 31, 2009
  6. mobbarley

    mobbarley Active Member

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    is that 100%? do you have a noise reduction feature in your cam? try turning it on/off? ps: no exif.
     
  7. Deepsix

    Deepsix OT Supporter

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    long exposure noise reduction is on, i should keep it on yeah?
     
  8. mobbarley

    mobbarley Active Member

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    probably, but you can try without. are there any firmware updates for you camera?

    it also looks very underexposed, F22 is probably unnecessary.
     
  9. Deepsix

    Deepsix OT Supporter

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    i used f/22 just for a first shot and didnt have time to try another last night. i was really only guessing on the 8 minute exposure. now i have a better idea for the next clear(er) night.

    what would be ideal star trail settings?
    max zoom, min iso, mid aperture?
     
  10. Deepsix

    Deepsix OT Supporter

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    this one turned out alright except i had forgotten to change iso to 100 and ended up shooting a few in 1600.

    [​IMG]
     
  11. mobbarley

    mobbarley Active Member

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    my completely unscientific approach if the sky is very dark - set a mid line aperture and iso100 and leave the shutter open as long as you want and it doesn't seem to become overexposed, i've only done around 30 mins though.
     
  12. asdfbunk

    asdfbunk A Member OT Supporter

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    no risk of sensor overheating? i've only heard of that for loooong exposures, so I don't know :hs:
     
  13. mobbarley

    mobbarley Active Member

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    overheating? no, there would be a warning in the manual. it may get warm and produce some artifacts, but I think thats it.
     
  14. xenon supra

    xenon supra OT Supporter

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    From what I've read you should shoot at your lowest "base" ISO.

    This means if your camera does 200-6400 and then has Low-1 for ISO 100 and HI-1 for 12800. you should be shooting at 200.

    because its not really ISO 100, it has to do with some shit I don't understand. anyone know what I mean?
     
  15. adamlewis88

    adamlewis88 New Member

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    You have native ISOs and then expanded ISOs. Expanded ISOs are simply the nearest full stop pushed or pulled a full stop in camera. 100 ISO on your D700 is actually 200 ISO overxposed and brought back down a stop. It allows you to get the same shutter as you would if you were actually shooting at 100 ISO but you lose DR and highlight headroom. 12800 is 6400 underexposed and pushed a full stop. It allows you to get the same shutter as you would if you were actually shooting at 12800 but youll get a lot more noise from pushing an already underexposed shot.

    On many cameras, this also applies somewhat to intermediate ISOs and is why you should always shoot at full stop ISOs. Many cameras will push and pull a base ISO 1/3 to get those intermediate ISO numbers. So 160 is 200 -1/3, 250 is 200 +1/3, and 320 is 400 -1/3. Make sense?

    Some cameras only push(5D classic). That would be 125 is 100 +1/3, 160 is 100 +2/3, 250 is 200 +1/3, and so on

    Thats the gist of it, but even that is not entirely accurate. Last I read, the "real" ISOs stop at 3200 on the D700/D3/D300. Same thing on the 5D2. However, at least Canon has a true 100 ISO and doesnt have to cheat!
     
  16. xenon supra

    xenon supra OT Supporter

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    ISO stops at 6400 on my D700, I'd assume its same for the D3

    The 300 does stop at 3200 though.

    true ISO 100 ftw :cool:
     
  17. adamlewis88

    adamlewis88 New Member

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    Heres a noise chart for the 5D2
    [​IMG]

    You can see how the camera manipulates base ISO numbers to get intermediate numbers and how many times, shooting at a higher base ISO will give you less noise than shooting at a lower intermediate ISO (that is a pushed base ISO)
     
  18. Deepsix

    Deepsix OT Supporter

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    ASA/ISO range 100–1600 in 1 EV steps, 3200 in extended mode


    looks like my 20d should be good for 100iso
     
  19. asdfbunk

    asdfbunk A Member OT Supporter

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    It seems the ones right before the base ISOs have even lower noise levels

    160, 640, etc
     
  20. adamlewis88

    adamlewis88 New Member

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    Anytime you take a shot and pull it down, youll get less noise. 160 is 200 pulled down 1/3 and 640 is 800 pulled down a third. You get less noise but you also lose DR and highlight headroom.
     
  21. EWhytsell

    EWhytsell New Member

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    ISO won't matter in an 8 minute shot. Your getting noise due to heating of the sensor and thats normal. It shouldn't burn up your sensor unless your using a point and shoot in 90 degree ambient temps.

    If your gonna shoot star trails it would be best to use the highest non-expanded ISO (not sure why we dont' use the expanded settings, but we don't.)

    For settings you should probably use like ISO 1600 shutter speed 15-30 seconds and aperture as wide as you want.
    Next set up the camera to take those frames for around 2 hours and then stack them all in your favorite program and you should have some really nice trails. Also TURN OFF noise reduction. You won't need it and it will just delay your shots.

    If you want to get really clean shots shoot about 20 more frames of the same shutter time with the lens cap on and use a more advanced program such as deep sky stacker to apply them to your star trail frames to make your own very effective noise cancellation.


    Here's an example of what I'm talking about

    Single 2 minute or so exposure

    [​IMG]

    Something like 20 of those combined using the technique I talked about

    [​IMG]
     
  22. asdfbunk

    asdfbunk A Member OT Supporter

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    Yeah but 160 is lower than 100, and 640 lower than 400 :eek3:
     
  23. asdfbunk

    asdfbunk A Member OT Supporter

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    Is that to simulate the noise so it knows what to knock out? :dunno:
     
  24. EWhytsell

    EWhytsell New Member

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    Exactly. Just like the camera does except you get to save time. Ever noticed that on a 30 sec shot you camera's noise reduction takes an extra 30 seconds for that picture to finish? Its making the dark frame in camera and then subtracting it from the image to eliminate hotpixels, reduce banding and I'm sure other things.

    Doing all dark frames after your finished shooting saves time and if you want you can even shoot the dark frames on a different day as long as the ambient temp is +/-5 degrees of the day you were shooting the light frames on. Lots of astrophotographers build a dark frame library to use in processing.

    Also if your lens produces vignetting you can reduce it greatly by shooting what we call a flat field. Look that one up, its interesting.
     
  25. Deepsix

    Deepsix OT Supporter

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    what's a good program for stacking the shots on mac? Can lightroom do that?
     

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