03-23-2017 02:56 PM
I have just purchased a EF Extender 2x III and am attaching this to my 5D Mk IV EOS Camera with a EF 100 - 400 1:4.5-5.6 L IS USM lens. The AF switches off when the extender is in place and 'Manual Focus' shows in the display on top of the camera. Removing the Extender and re-attaching the lens returns the camera to AF AI Servo. What am I doing wrong or what have I not done i.e. do I need to tell the camera that the extender is there? Any help gratefully received.
03-23-2017 03:34 PM
@jcc285 wrote:I have just purchased a EF Extender 2x III and am attaching this to my 5D Mk IV EOS Camera with a EF 100 - 400 1:4.5-5.6 L IS USM lens. The AF switches off when the extender is in place and 'Manual Focus' shows in the display on top of the camera. Removing the Extender and re-attaching the lens returns the camera to AF AI Servo. What am I doing wrong or what have I not done i.e. do I need to tell the camera that the extender is there? Any help gratefully received.
This is normal for this lens. When you mount a 2X extender, you lose 2 f/stops so with this lens with an f/5.6, it becomes an f/11 lens and your camera can only focus with f/8 or less. You should return and get a 1.4X which will maintain focus with this camera/lens combo.
03-23-2017 03:51 PM
03-23-2017 05:31 PM
Actually, very few Canon cameras (only the high end ones) will AF with an f/8 lens. Most max out at f/5.6.
03-25-2017 12:06 PM
You can use a 1.4x extender with the 100-400mm lens ... which takes it to f/8. That's still allows for working auto-focus.
The 2x extender was meant for f/2.8 lenses (which takes them to f/5.6) but since the 5D IV can focus up to f/8, you can get away with using it on an f/4 lens (which takes it to f/8).
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