AF works best at maximum aperture (i.e. smallest f/stop number). Not sure what you mean by "working aperture". EF lenses are used at full aperture for focusing and framing (i.e. when you look through your eyepiece). Only for the actual exposure (and of course for DOF preview) does the lens stop down to the metered aperture.
High-end Canon bodies have center-point AF which work at f/8 instead of the usual f/5.6, at the expense of being bit less accurate. Lars -- .~. Lars Michael /V\ [EMAIL PROTECTED] /(_)\ http://www.larsmichael.com/ ^^ ^^ * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
