When fixing exposure on underexposed digital photos i get lots of noise. What's

What program are you using to correct the photos? Most of the time the better the program, the better the photo will come out. The more you play around with a digital photo the more quality you will lose. But, programs can only do so much. The digital photo must have the "information" needed. So, when you correct exposure, if the information needed isn't there, the quality isn't there.

Essentially CCD sensors are extremely dense and susceptible to noise. Like any electrical device, the individual sensors on a CCD have a fixed level of noise. When you have a properly exposed photo, you have a high signal:noise ratio and the noise is relatively insignificant, but when your signal is weak (i.e. low light) your s:n ratio is low and noise becomes a factor. By fixing exposure digitally you're amplifying both signal and noise and therefore it becomes more obvious. If you want low light capability, your only real choice is a DSLR, their larger sensors have better sensitivity. Also, Canon DSLR's tend to have CMOS sensors which are less noise prone as well (fewer electrical components).