Exposure Experiment

I have a couple of ways of explaining how a camera determines exposure and why it sometimes gets it wrong, but despite my best efforts it seems to be a concept that continues to elude many people. Well, I've come up with a new way. A way that requires few words and should demonstrate the concept in a matter of minutes. Curious? Do the following:

• Grab your camera
• Put it on "Auto"
  
• Take a picture of something black that will fill the frame. It must be 100% black. Perhaps you could do a close-up of a blank black T-shirt so that the material fills the entire frame.
• Take a picture of something completely white that will fill the frame completely. A close-up of a white sheet of paper or a white wall should do.
  
• Compare the two photos

Questions? Comments? Leave them here or on my "Photography_Beginners" yahoogroup.