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I have a Canon 7D and am trying to use a 1.4 converter with

Customer Question
the 100-400mmL IS II lens...
I have a Canon 7D and am trying to use a 1.4 converter with the 100-400mmL IS II lens. I can't get auto focus to work. Auto focus works without the converter. What am I doing wrong?
Submitted: 2 years ago.Category: Camera and Video
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8/29/2015
Camera and Video Technician: Rick, Camera and Video Technician replied 2 years ago
Rick
Rick, Camera and Video Technician
Category: Camera and Video
Satisfied Customers: 1,714
Experience: 30+ years experience as a camera and video technician.
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Hi. My name is*****'m a camera repair technician with over 20years in the business and I'll be glad to help you with your question today.

Canon cameras Need minimum light level to work. Usually around f8. Doublers and tele-extenders will rob the camera of the light needed to work properly and therefore, no AF unless the light levels are present to accommodate this.

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Customer reply replied 2 years ago
if I show f8 or 9 or 10 it should focus?
Customer reply replied 2 years ago
I set a higher f stop and nothing.
Camera and Video Technician: Rick, Camera and Video Technician replied 2 years ago

Actually, the lens won't AF unless the f stop is 5.6 or brighter.

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Customer reply replied 2 years ago
I shot a picture with manual focus yesterday with f10, ISO1250 at 560mm because it would not auto focus.
Camera and Video Technician: Rick, Camera and Video Technician replied 2 years ago

Yes but the AF will only work at f8 or better.

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