Quote Originally Posted by Sheiky
I must notice that I have had two the same pictures just taken moments after each other, but exactly the same composition, same light, same everything except for focus maybe (macro shots)...one could fail and one is good. How could you explain that then? I thought it was a mechanical error. And when I'm talking about noise at ISO100 I mean NOISE.... like iso3200 noise. Still kicking myself for throwing away those pictures so fast....

Could be something is broken. If it happens again, post the raw files (the 1 noisy and the other OK) and I'll see if I can help. Some 50D owners have had to send their camera in for repair before, but it's rare.