Daniel,


Does this mean that the iris diameterchanges when zooming a 70-200 @ f/2.8 from 70 to 200?


If I were to shoot an evenly illuminatedwhite screen (16 ft/L)at 70mm and at 200mm, both shots at f/2.8, it seems like there would be less total light available at 200mm since I would be shooting a smaller area of screen, thus less available Lamberts. For the total light to be equal, given the same ISO and shutter speed, it seemsit would make sense ifthe focal length and iris diameter correlate inversely to maintain an equivalent f-stop. If the iris diameter is constant, then wouldn't something have to give? Shutter speed?