Canon RF 100-400 Autofocus problem

[Len29]

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.

[jrhoffman75]

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@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.

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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.

[rs-eos]

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

[wgeoghegan]

I had no idea that happened while I was taking pictures. Lost lots of shots. I thought  the lens was bad.

There are so many choices on the R6 that just understanding what each one means is a struggle. I wish the manual were set up differently so for example if one looked up autofocus everything would be on one or a few pages. As it is currently 19 different pages come up on a search of the manual for autofocus.

[wgeoghegan]

So, yes I was using the RF 100-400 lens with my R6 and my shots were blurred at 400 mm. My shots at 100 mm were fine.