I know what you mean. Mod 2 of my course uses a grey card test to teach us the latitude of our camera sensors (+3 to -4 EV for mine a total of 7 stops). In doing so I also found that my 40D typically underexposes by around 1/3rd stop at ISO100. Useful exercise though and really helped me understand how to get the best out of the camera/sensor.

As a newcomer I've been really impressed by those of you that regularly try to help others - keeps me coming back every day!

Regards