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New Contributor
Posts: 2
Registered: ‎03-23-2017

Canon 2x III Extender

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.

 

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Respected Contributor
Posts: 1,119
Registered: ‎02-06-2013

Re: Canon 2x III Extender


@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.

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New Contributor
Posts: 2
Registered: ‎03-23-2017

Re: Canon 2x III Extender

Thank you, I hadn't understood that the camera would only focus at
f/8
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Honored Contributor
Posts: 7,158
Registered: ‎11-13-2012

Re: Canon 2x III Extender

Actually, very few Canon cameras (only the high end ones) will AF with an f/8 lens. Most max out at f/5.6. 

John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, MX472, LR Classic
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Esteemed Contributor
Posts: 3,850
Registered: ‎06-11-2013

Re: Canon 2x III Extender

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).

 

Tim Campbell
5D III, 5D IV, 60Da
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