Picture Quality Problems

Discussion in 'Digital Photography' started by mattyb240, Feb 25, 2009.

  1. mattyb240 macrumors 6502a

    Joined:
    May 11, 2008
    #1
    Right, I have been having some problems (only today has it started) but one of my images I noticed the dark clouds in the shot almost look noisy and I don't really know why as I was shooting with a low iso? The second problem is that when my MBP 15" Anti Glare goes to the desktop after screen saver, the image looks appalling and massively grainy!

    Does anyone know what this could be down to?

    Here is the image I am referring to:
     

    Attached Files:

  2. Doylem macrumors 68040

    Doylem

    Joined:
    Dec 30, 2006
    Location:
    Wherever I hang my hat...
    #2
    Low ISO won't guarantee your pics are noise-free when your exposures are in whole seconds, and this looks like a pretty long exposure...
     
  3. ChrisA macrumors G4

    Joined:
    Jan 5, 2006
    Location:
    Redondo Beach, California
    #3
    Yes there are two sources of noise. The first is "shot noise" and this is what we see in "normal" photos. It is caused by the fact the light is carried by photons which are discrete events. Light is not a continuous signal so it is just a matter of luck if a pixels sees one or two more or less photons. It's the statistics of small numbers that causes this kind of noise.

    The second noise source is normally a non-issue. That is "thermal noise". The CCD sensor is designed to convert photons to electric charge but the CCD itself generates some thermal photons. If you were to expose long enough even with a lens cap on in time you would get a pure white image.

    Some camera have a system where you can take a "dark exposure" (with the shutter closed" and then subtract that from the real image. See if your camera can do a dark frame subtraction. This will not remove the random nature of the noise but many times the thermal noise has a pattern because for example the CCD has a temperature gradient.
     
  4. toxic macrumors 68000

    Joined:
    Nov 9, 2008
    #4
    just for the record, Canons use CMOS.

    anyway, there should be a custom function in your camera, something along the lines of "turn on noise reduction for long exposures." i've never used it, but i believe that's what your looking for. note that the camera will be unusable right after the shot. so say you did a 30-sec exposure, then the camera will be unusable for another 30 seconds after that. something along those lines.
     
  5. mattyb240 thread starter macrumors 6502a

    Joined:
    May 11, 2008
    #5
    Is the noise as evident on your screens? And yes it was a 10 second exposure, but I will definitely look up that custom function on my Canon. Its a shame really, I really like that shot, I'm hoping it wont be as evident in a print? Would using photoshop to perform a noise reduction help at all?
     
  6. mattyb240 thread starter macrumors 6502a

    Joined:
    May 11, 2008
    #6
    Just thought I'd give this a quick bump for some answers to my questions above, and also I spoke to the head photographer on campus today, and he has very generously offered to help me calibrate my laptop display, so I am very excited to see the results!
     

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