Bert, I've just skimmed through the piece to which you refer. An interesting read!
But I lifted this bit from the Canon blurb....
"The brighter the light that hits the photodiode, the greater the electrical charge that will accumulate within it"
I have a problem with this. For a more complete explanation see here
http://en.wikipedia.org/wiki/Photoelectric_effect
Hence I suspect my understanding of photodiodes is not up to par...or perhaps Canon are simplifying things a tad..
