> think this is because the non L lenses use > 'backfocus' and the L lenses > have to move much more glass when focusing.
Not true: not all L lenses use Internal Focus. Some may use rear focus (Backfocus). The back focus/internal forcus is due to the "ring" USM by design (and not because of the L designation). Case in point the 80-200F2.8L > The reason for this seems to be that the L lenses > can use the extender with > the protruding front. Again not correct: the 80-200F2.8L is not compatible with the extenders as well since it uses rear focus: http://www.photo.net/bboard/q-and-a-fetch-msg.tcl?msg_id=0000UJ In your case, it is coincidental that both lenses use Inner Focus due to Ring Type USM by design. > Now my question, if a lot of people don't see that > many difference when > using a third party extender ... wasn't it better to > have backfocus on L > lenses and change the extender .... Not sure why Canon made it so it protrudes - maybe they want to make the older generation of lenses incompatible ? - Harman __________________________________ Do you Yahoo!? New and Improved Yahoo! Mail - 100MB free storage! http://promotions.yahoo.com/new_mail * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
