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Canon RF 100-400 Autofocus problem

Len29
Contributor

Hello,

Does anybody have an issue with autofocusing in 400mm with this lens? When I extend the lens to 400mm and try to focus, the lens is not focusing. I have to retract the lens to 100mm and refocus. Only then autofocus works. It happens almost every time in any mode(M,Av,Tv or Fv). Camera Canon R6.

1 ACCEPTED SOLUTION

I just reset the camera setting and the default is "on" for this setting. 

from the canon r6 manual below instructions need to be expended:

Len29_0-1677543525510.png

 

View solution in original post

13 REPLIES 13

rs-eos
Elite

I don't own this lens, but just a couple questions to help troubleshoot:

  • If you adjust the zoom just a bit less than 400mm, does it then work? i.e. does it fail only when exactly at 400mm?
  • Any differences if the stabilizer is on vs off?
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Ricky

Camera: EOS 5D IV, EF 50mm f/1.2L, EF 135mm f/2L
Lighting: Profoto Lights & Modifiers

This is my second RF100-400 IS USM lens. Both behave the same, whether IS is ON or OFF. The autofocus is not working when I extend the lens to 400mm and it's out of focus no matter which button I use(back buttons or main release button). I tried to gradually zoom out while holding AF button and sometimes it start focusing at around 135mm. But most of the time I have to retract the lens to 100mm in order for lens to start autofocusing. 

If you have other RF Mount lenses do they work correctly on this camera.

-Demetrius

Current Gear: EOS 5D Mark IV, EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 50 F/1.8 STM, EF 85mm F/1.8 USM, EF 70-200mm F/2.8L IS III USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D & Sigma 17-50mm F/2.8 EX DC OS HSM


-Demetrius

Current Gear: EOS 5D Mark IV, EF F/2.8 Trinity, EF 50mm F/1.8 STM, EF 85mm F/1.8 USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D

Len29
Contributor

Update: The "problem" is solved. In the menu; AF; #4; "Lens drive when AF impossible" was OFF. When I changed it to ON, AF is working without any problem.

You shouldn't have to enable that setting to force the lens to focus.

This is sounding like you have an issue with the camera.  I would first reset all settings and try things out again.   If the issue remains, you probably should look at sending it in for a repair.

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Ricky

Camera: EOS 5D IV, EF 50mm f/1.2L, EF 135mm f/2L
Lighting: Profoto Lights & Modifiers

Thanks, You may be right. My other RF24-105 L f/4 lens is not doing this. But it's not 100-400mm zoom. I'm going to call Canon tech support tomorrow about this, will see what they say.

I called Canon tech support today regarding my issue. Their response was: Your lens and camera work within the normal operation. And they suggest using "Lens drive when AF impossible" and "Continue focus search: ON.


@rs-eos wrote:

You shouldn't have to enable that setting to force the lens to focus.

This is sounding like you have an issue with the camera.  I would first reset all settings and try things out again.   If the issue remains, you probably should look at sending it in for a repair.


That is exactly what the problem is. Long telephoto lens can get grossly out of focus so the camera can't "see" anything to start focusing on. I had the exact same problem with my 1D X MkIII. I had utilized some recommended settings from an online user. Lens wouldn't focus when I was trying to focus on ospreys flying.  If I manually focused to get the birds close then it focused OK.

If I switched out of the custom settings back to my basic it worked fine.  Took a while to sort out the problem.

John Hoffman
Conway, NH

1D X Mark III, M200, Many lenses, Pixma PRO-100, Pixma TR8620a, Lr Classic

Thank you for this added explanation, John!  I had assumed incorrectly about the default value of that setting as well.

--
Ricky

Camera: EOS 5D IV, EF 50mm f/1.2L, EF 135mm f/2L
Lighting: Profoto Lights & Modifiers
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