I see you have the 17-40L - is it good? I am hoping to order one tomorrow - Couldn't find a nice 28-70 f2.8L and the 24-70 f2.8L is too expensive for me.
Also I shoot 1/3 stop under. On the back of the camera things looks fairly good so I left the settings as changed and came home excited to see my shots.
I'm wondering why you are underexposing, it's just about the worst thing you can do if you are worried about high iso noise. This used to be the thing to do with slide film but not on a digi SLR.
Also looking at the shot on the screen is usually not much use to judge anything but framing in my opinion, use the histogram if you like to make sure you are not blowing the highlights but that's about it.
Not sure if the 40D and 50D have the same exposure algirithm but my 40D now sits almost permanantly at plus 1/3 stop, and no I don't think there is anything wrong with the camera I just prefer the images like that as a better place to start my RAW workflow.
HTH
David
Caught this thread a few weeks ago after experiencing what i think are very unacceptable levels of noise with the 50D. Turned off the the stuff as recommended and last weekend I had chance to try it out - went to Gigrin Farm in Mid Wales to see a Black Kite.
The light was fairly good when we got there but to maiantain good speeds on the camera I shot at 400 iso. Also I shoot 1/3 stop under. On the back of the camera things looks fairly good so I left the settings as changed and came home excited to see my shots.
must say I was even more distraught than previously. Spend a few days mulling over the stuff and have seriously considered moving over to Nikon and going to one camera - I also have a 5D.
Went in my local camera shop today and they have asked me to take it in and they will send it off to Canon for them to look at. Right now I wish I had bought the 40D but the 50D had been out a little while and 40D's wrre a little scare on the ground..... groan.