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Russell H.
Russell H., Service Tech
Category: Camera and Video
Satisfied Customers: 11066
Experience:  8+ years of professional experience
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I have a 5d3 and a new 100-400tele lens with a new 1.4

Customer Question

i have a 5d3 and a new 100-400tele lens with a new 1.4 series extender and cannot get
AF to work???? Help As I have tried all the tricks i know.charles
Submitted: 1 year ago.
Category: Camera and Video
Expert:  Russell H. replied 1 year ago.

Hi, thank you for contacting My name is Russell. I will do my best to provide the right answer to your question.

The extender may cut off the lens from the electronic contacts on the camera body. Those have to 'get through' their signals to the corresponding contacts on the lens assembly, in order for Auto Focus (or any other automatic function involving the lens) to work.

I presume that that 100-400 tele lens works fine without the extender in place. Correct me if I'm wrong, and I will amend my answer as needed.

Customer: replied 1 year ago.
Without the extender ,it seems to work okay. .with the extender,it does not work
Expert:  Russell H. replied 1 year ago.

OK, then it must be because the extender cuts off the connection between camera body lens-mount contacts, and the corresponding contacts on the lens assembly.

You can still use the lens in Manual mode.

(If this answers your question, please rate my answer. Thanks.)