17-40 1:4 L Autofocus

[winminn]

Lens is sometimes very slow to autofocus and sometimes does not focus at all.  Any suggestions what could be wrong?

[kvbarkley]

What camera?

How much light?

[ebiggs1]

"Lens is sometimes very slow to autofocus and sometimes does not focus at all.'

A better question is, has it always been that way?  Or, has it just developed that issue?

[winminn]

Bright light with 7D Mark II

[winminn]

Has it always been slow and sometimes nonreponsive?  NO.

[jrhoffman75]

What is the subject? Does it have suffiecient contrast? Are you in One Shot mode? What happens if you arfe in A+ Green Square? Is it just this lens?

[ebiggs1]

"Is it just this lens?"

This is the next question.  In order to analyze this we need to go in a specific order.

[winminn]

I have found that when the autofocus does not activate, it can help to point at something close at hand.  That sometimes helps, not always. If it "wakes up" from that act, then it seems to be okay.  However, it's still slowl

[winminn]

Please suggest the specific order that I should undertake, per your suggestion.  Thank you.

[ebiggs1]

Ok first, like I asked is this all of a sudden or has it always been this way?  Second, does it act this same way on  several different cameras.

I think I remember you said it has always been this slow.  So now you need to get another camera and try it.  If it is the same it is the lens not the camera.  Let's suppose it is the lens. Go outside on a nice day and try it.  Good contrast so the AF has all ther info it needs. Is it doing its thing?  Poor light will slow even the fastest lens.  If it works as it should the lens is probably OK.

Lastly has the lens ever gotten wet or been dropped?  If no, the lens is probably OK.  if it did see some rough use send it to Canon for a C&C.