In article <45toul$74k@iac2.ltec.net>, rd34029@ltec.netÒ says...
>I was looking at my TTL flash for my F4 the other day, when I couldn't
>figure out how the reflected light was measured.

Without film in the camera, place it on "B", hold the shutter release
in while you open the camera back (it takes only 3 hands) and look in
to the mirror chamber with the shutter open. Voila! A meter cell facing
upward at an angle toward the film (to meter the flash light reflected off the film during the flash exposure - pretty neat, huh?).
Hope this helps.