Actually a saw a good article on "ISO standards" in one of my photo rags, and amazingly enough, ISO ratings on many brands and models of cameras were off...in some cases, nearly a full stop. One of my cameras (D300) was listed at 1/2 stop under what you thought it was. I was able to compensate for that in custom settings. It's like the days of muscle cars, for the sake of insurance premiums, many of the car manufacturers grossly under rated their cars horsepower...but don't ask me why the camera guys are so inaccurate
