Need help with AF issue on 80D w/extender: Just bought a Canon 2X extender for my 80D and EF 100-400 ll. I can't get it to AF at any F stop. Any ideas ? Thanks...

dmc Loc: Montgomery, AL

Just bought a Canon 2X extender for my 80D and EF 100-400 ll. I can't get it to AF at any F stop. Any ideas ? Thanks...

rwilson1942 Loc: Houston, TX

Most AF systems will not work if the maximum aperture is less than f8.
With a 2X on that lens you would have f9 so I would not expect AF to work.

dmc Loc: Montgomery, AL

The Canon 80D is supposed to be able to AF at F8. And like I said I tried at F16 and beyond. I also tried single point AF but still get 'MF' on the screen.

TriX Loc: Raleigh, NC

dmc wrote:

The Canon 80D is supposed to be able to AF at F8. And like I said I tried at F16 and beyond. I also tried single point AF but still get 'MF' on the screen.

Since the lens is an f4.5-f5.6, with a 2x extender, the new max aperture with the extender is f9 - f11 depending on the Focal length. Since the 80D will not autofocus beyond f8, this combination will not AF no matter how you set the aperture. Your options are trading the extender for a 1.4X or using manual focus.

rwilson1942 Loc: Houston, TX

dmc wrote:

The Canon 80D is supposed to be able to AF at F8. And like I said I tried at F16 and beyond. I also tried single point AF but still get 'MF' on the screen.

I think you misunderstood, you need an aperture larger than f8 (like f5.6) not an f number bigger than f8 (like f16)

dmc Loc: Montgomery, AL

Ok, I think I finally understand. But I did find out that while using the 2X you can focus in 'Live View', then switch to MF and compose thru the view finder.

I might try that for a while but I can see trading the 2X for a 1.4X in the future. Thanks for the help.

CHG_CANON Loc: the Windy City

dmc wrote:

Just bought a Canon 2X extender for my 80D and EF 100-400 ll. I can't get it to AF at any F stop. Any ideas ? Thanks...

As of Jan 2018 a Canon EF 2x extender cannot be used with any EOS body and an EF 100-400L I or II lens and retain Auto Focus.

Why?

The EF 100-400L zoom models have variable maximum aperture values at different focal lengths. At 100mm for the mark II lens, the maximum aperture is f/4.5. With a 2x converter, the maximum aperture is f/9. Your specific 80D User Manual documents f/8 as the minimum aperture needed for autofocus on this model. The same User Manual also lists out the all various lenses and the converter models supported by this EOS body. Refer to Section 3 - Setting the AF and Drive Modes, starting on page 115.

You should exchange the 2x for a 1.4x III or return for refund.

Note on page 131 of 80D Instruction Manual

Bill_de Loc: US

dmc wrote:

Ok, I think I finally understand. But I did find out that while using the 2X you can focus in 'Live View', then switch to MF and compose thru the view finder.

I might try that for a while but I can see trading the 2X for a 1.4X in the future. Thanks for the help.

Instead of switching from live view to viewfinder, try manually focusing through the viewfinder. Your camera may even have a focus confirmation.

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mwsilvers Loc: Central New Jersey

dmc wrote:

The Canon 80D is supposed to be able to AF at F8. And like I said I tried at F16 and beyond. I also tried single point AF but still get 'MF' on the screen.

You are confusing stopping down to smaller apertures vs a lenses maximum aperture. Your camera is capable of AF with lenses that have a maximum aperture of f/8 and wider. The f/8 capability, which is becoming more common these days, is specifically to support use of an extender. Your lens natively has a maximum aperture of f/4.5 - 5.6. Mounting a 2x extender to that lens changes the maximum aperture by 2 stops so your lens' maximum aperture is then f/9 -11. There is no commercial camera which will autofocus with a 2x extender on that lens.

Now, if you had purchased a 1.4 extender, it only would add one stop to the maximum aperture of your lens which would then have a maximum aperture f/6.3 -8 and would autofocus on your body.

The bottom line is there is absolutely no way you will get your lens to autofocus with the 2x extender. You can either buy a longer lens, manual focus, or get a 1.4 extender and crop the final images. Those are pretty much your only choices.

speters Loc: Grangeville/Idaho

TriX wrote:

Since the lens is an f4.5-f5.6, with a 2x extender, the new max aperture with the extender is f9 - f11 depending on the Focal length. Since the 80D will not autofocus beyond f8, this combination will not AF no matter how you set the aperture. Your options are trading the extender for a 1.4X or using manual focus.

dmc Loc: Montgomery, AL

[quote=CHG_CANON]As of Jan 2018 a Canon EF 2x extender cannot be used with any EOS body and an EF 100-400L I or II lens and retain Auto Focus.

Thanks Paul for you're explanation and advice, I appreciate it. At least I now know there isn't anything 'wrong' with the extender, just me. (I bought it used, but like new, on eBay.)

dmc Loc: Montgomery, AL

rwilson1942 wrote:

I think you misunderstood, you need an aperture larger than f8 (like f5.6) not an f number bigger than f8 (like f16)

Yes Rick...I did misunderstand. Seems like the older I get the more I get confused !!

dmc Loc: Montgomery, AL

TriX wrote:

Since the lens is an f4.5-f5.6, with a 2x extender, the new max aperture with the extender is f9 - f11 depending on the Focal length.

Thanks Chris...I appreciate your response and explanation. Seems like everybody knows whats going on but me !!

dmc Loc: Montgomery, AL

mwsilvers wrote:

You are confusing stopping down to smaller apertures vs a lenses maximum aperture. .

Thank you Mr. Silvers for you're input and advice. It's nice to know I can always find help, explanations and guidance on the Hog.

dmc Loc: Montgomery, AL

Bill_de wrote:

Instead of switching from live view to viewfinder, try manually focusing through the viewfinder. Your camera may even have a focus confirmation.

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Thanks Bill...I'll try that method out too.