I just got back from Jellystone and have a question concerning using Canon telephoto lenses (400 2.8 and 600). When I put these on the my camera (400D) the lenses won't focus until I monkey around with the lens "switches". Does any one know what "settings" I need to keep on these lenses so they focus immediately after I put them on my camera? Thanks, Steve
Edited by monsterdeer on Sep 20, 2007 at 04:38 PM GMT
Those lenses have a distance limiter switch. I'm pretty sure that if the lens is already focused to a distance not within the range of the switch when you attach it to the camera then AF may not work. You'd need to manually shift the focus distance or change the distance limiter switch setting in order to get the lens focus within the AF range of the switch. Then AF will work fine. Maximum versatility is achievable when the switch is in the minimum distance to infinity position.
On the plus side, limiting the AF focus distance can speed up the AF by not letting the lens go searching for focus outside the required range.
The IS switch and the IS Mode switch will not disable AF operation.
This focus issue happened alot when I changed lenses with the 600 and the 400. It always worked once I played with limiter switch, but it was a pain. This only occurred with the 600 and the 400--the 300 2.8 worked all the time. Got to be frustrating.
will the AF "hunt", or not move at all?
What is the subject, focus mode (AI servo?) on body and the lens, lighting situation (nighttime or daylight), and other shooting conditions.
what is the focus trigger, the shutter button 1/2 way, or the * button
if you try the wrong one, the lens will not focus!
Will these lenses focus on another body, but not yours
what have you tried
The AF just locked up and the red light or beep didn't turn on. Shot in shade alot--never too dark. Didn't have a second camera. Used a cable release and the actual button--tried everything. ISO 100-400. When I changed the switches it all began to work eventually. Strange.
After the lens began AF it never had a problem even in real low light (almost dark).
