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Rick
Rick, Camera and Video Technician
Category: Camera and Video
Satisfied Customers: 1704
Experience:  25+ years experience as a camera and video technician.
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I have a Canon 7D and am trying to use a 1.4 converter with

Customer Question

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: 1 year ago.
Category: Camera and Video
Expert:  Rick replied 1 year ago.

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.

Customer: replied 1 year ago.
if I show f8 or 9 or 10 it should focus?
Customer: replied 1 year ago.
I set a higher f stop and nothing.
Expert:  Rick replied 1 year ago.

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

Customer: replied 1 year ago.
I shot a picture with manual focus yesterday with f10, ISO1250 at 560mm because it would not auto focus.
Expert:  Rick replied 1 year ago.

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