PLEASE HELP--500mm AF Wont lock focus instantly on my 7D

[Amol Khedgikar]

Hi,

Yesterday I acquired a used 500mm in great shape.

when I took it out to test its functions and working condition, I noticed that the AF wont budge instantly. I had to move the focus ring manually close to the focus plane then the AF would move quickly and lock perfectly. This did not happen consistently. some times the focus moved and from infinity to a very close subject and locked quickly. But sometimes I had to prefocus manually (or at least move the focus ring) to get the AF going. Is this normal for this lens and canon 7D?

I have never used this lens before so I would not know. If its a problem then I would have to return the lens(took me years to save up and but a used one in the first place). The seller is reputed and did not mention this in his description. what AF and IS settings do I need to be looking at on the lens or the camera.

Please help.

[arash_hazeghi]

most likely it is operator error. You need to set the focus limiter switch on the lens and turn focus search option in your camera to ON.

[Dennis Zaebst]

Amol,

Arash is dead on in his reply. I had the exact same issue a few weeks ago. If C.Fn III-4 is not set to 0 (Focus Search on) the camera will fail to autofocus, or focus hesitantly if the lens is very far out of focus. Turning on focus search will force the camera to run through its entire distance range to find the focus (which will be slower and not instant if far out of focus). The fastest AF is when you have the distance switch set to the correct distance range (either 4.5 M to inf., 4.5 M - 10 M, or 10 M to inf.) with focus search off.

Try a more distant target with the distance switch on the lens set to 10 M - Inf., then move to another target not far out of range of the first one, and the focus should be very fast.

It took me a while to figure this out too! Good luck with your new lens. It's a great one.