08-02-2007, 09:27 AM
|
 |
Critique | Share My Shots Moderator
|
|
Join Date: Dec 2006
Location: Kansas City, USA
Posts: 1,916
|
|
From the canon knowledge database:
Quote:
Issue: Autofocus does not work
Solution: The camera is unable to auto focus when the maximum working aperture falls below f/5.6.
In order to maintain autofocus capabilities, the lens must maintain at maximum working aperture of at least f/5.6 or greater.
If a 1.4x EF Extender is used on a lens that has a maximum working aperture of f/4 or greater, the camera will continue to be able to autofocus. If the same extender is used on a lens with a maximum aperture smaller than f/4, the maximum working aperture will be smaller than f/5.6, so auto focus will not be possible.
If a 2x EF Extender is used on a lens that has a maximum working aperture of f/2.8 or greater, the camera will continue to be able to autofocus. If the same extender is used on a lens with a maximum aperture smaller than f/2.8, the maximum working aperture will be smaller than f/5.6, so auto focus will not be possible.
|
|