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EF 100-400mm f/4.5-5.6L IS II USM Autofocus suddenly not working


Had this lens since Sep 2019 and worked beautifully for about 6-7 months and I've started noticing issues with it's AF for a couple months. 


I mainly shoot birds, f/5.6 to f/8. IS mode set to 2 on the lens for movement. AI Servo on the camera body. Av mode on the camera body so it chooses the shutter speed, I only change the f-stop sometimes and possibly the ISO but not much (maybe 2-400). Like I said, it worked great for months and months had no issues.


Now with everything being exactly the same and still using multiple point AF it will not consistently focus on the bird I'm aiming directly at and clearly have in my sights. Press the shutter halfway down, you can hear the motors in the lens trying to work and it just doesn't focus on the subject anymore. Every now and then I might get lucky based on proximity.


I called Canon today and was on the phone 20 minutes explaining the issue. He said I would receive Emails with directions on mailing the lens to them. He repeated my Email address back to me perfectly and I have not received any notifications.


Should I clean the lens without the caps off in any way? Should I do anything before sending it or taking it to repair? Any help anyone can provide is much appreciated. I've taken great care of it and I kind of expect a $2k piece of equipment to work properly. 




"...what harm did that do?"


Nothing, it's your camera. The advice is just a suggestion of what I have seen work over decades of photography experience.


"Autofocus suddenly not working"


This was the question, the reset confirms only that the camera/lens is working properly and the problem exists elsewhere.

Ultimately you have to do what you deem is right.

EOS 1DX and 1D Mk IV and several lenses!

"I may try that at some point with the custom settings."


Yes stop!  You need to get back to square one first.  Do the reset and the daylight outdoor test.

"I still feel like it may be a camera setting I changed..."

You are right and you are going to chase your tail unless you start over.

EOS 1DX and 1D Mk IV and several lenses!

@canonbirds wrote:

Yes, I've used my 18-135 on the camera and the AF seems to work fine. It's a less capable lens so it's difficult to compare it much more than that. Doesn't have an ultrasonic motor like the lens in question has. I feel like these motors inside the lens are too loud but I could be wrong.


The 100-400 just doesn't want to focus lightning quick anymore on the subject and sometimes just doesn't at all.



Thanks for responding, appreciated.

If the AF motors are suddenly louder than they were in the past, then contact Canon again.  Your lens needs service.

"The right mouse button is your friend."


Your settings sound reasonable.  Check your distance switch.  The lens focuses faster on the 3-meter to Infinity range on distant objects.  Are you using a teleconverter?  What camera body are you using?

"The right mouse button is your friend."

I've always had the distance switch set to Infinity and not Full I believe. I am not using a teleconverter or anything else on the lens, never used a hood either. Should I clean the actual lens? Could there be moisture or something blocking the AF from working properly?


Camera body is the 7D Mark II