What does "noise" mean in digital photography?

Question

What does "noise" mean in digital photography?

Answer 1

When you watch a weak TV signal (analog TV signal), you see noise lines on the screen. Similarly, when you shoot a digital photo in poor light conditions you get noise. You will see this when your camera uses a high ISO number or speed to make up for low light conditions. CCD devices used in cameras have their internal noise level when the "well" in the CCD is nearly empty (i.e., low light condition). Noise is related to the CCD's temperature and becomes an issue when the CCD is used in warm climates. For this reason CCD cameras used for Astro-photogrphy have special cooling devices that take the CCD chip to 25 to 50 degree lower than ambient. Noise is an unwanted electrical phenomenon. CMOS devices used in cameras also have noise problem and this can not be overcome by cooling the CMOS chip because they are not suitable for long exposures.

One more thing. When the "well" in the CCD is filled up due to extremely bright lighting conditions, you get another problem called "blooming". The contents of the "well" spill on to adjacent wells causing white streaking. Cameras use a technique called "white balancing" to compensate this "blooming". But it all depends on the contrast of the scene that you are shooting.

I have tried to put a lot tech stuff in ths answer, sorry cant reduce it further or make it simpler

Answer 2

Noise is a side effect of amplifing the signal that the camera pick ups.  As you increase the cameras sensitivity to light (usually by using the ISO function) the camera will have more chance of a useful exposure in lower light.  The sie effect is that  if the amplification is over applied, or poorly handled, the image appears gritty or fine detail becomes smudged.

Most DSLRs handle this problem fairly well these days, particualry if you are willing to use the raw format and do a wee bit of work in your pc afterwards.  Compacts are pretty renownked for being 'noisy'.

Answer 3

In film, it's grain.  In digital, there is no real name, so we call it noise.  It's basically grain, making your photos look grainy or have extra texture, but showing up especially in dark areas or when you use a high ISO.