Picture Quality Problems

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...

Doylem said:

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...

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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.

ChrisA said:

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.

Click to expand...

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.