topic Re: 17-40 1:4 L Autofocus in EF & RF Lenses

17-40 1:4 L Autofocus

winminn — Thu, 02 Aug 2018 18:37:02 GMT

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

Re: 17-40 1:4 L Autofocus

kvbarkley — Thu, 02 Aug 2018 18:41:13 GMT

What camera?

How much light?

Re: 17-40 1:4 L Autofocus

ebiggs1 — Thu, 02 Aug 2018 20:42:13 GMT

"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?

Re: 17-40 1:4 L Autofocus

winminn — Thu, 02 Aug 2018 21:20:43 GMT

Bright light with 7D Mark II

Re: 17-40 1:4 L Autofocus

winminn — Thu, 02 Aug 2018 21:21:39 GMT

Has it always been slow and sometimes nonreponsive? NO.

Re: 17-40 1:4 L Autofocus

jrhoffman75 — Fri, 03 Aug 2018 00:37:16 GMT

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?

Re: 17-40 1:4 L Autofocus

ebiggs1 — Fri, 03 Aug 2018 00:51:28 GMT

"Is it just this lens?"

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

Re: 17-40 1:4 L Autofocus

winminn — Fri, 03 Aug 2018 01:51:53 GMT

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

Re: 17-40 1:4 L Autofocus

winminn — Fri, 03 Aug 2018 01:52:58 GMT

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

Re: 17-40 1:4 L Autofocus

ebiggs1 — Fri, 03 Aug 2018 14:51:57 GMT

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.

Re: 17-40 1:4 L Autofocus

Waddizzle — Sat, 04 Aug 2018 12:48:06 GMT

@winminn wrote:
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

Just this lens, huh. Some lenses do not transition well from focusing at near infinity, to focusing at near the MFD. Your remark about “wakes up” is what brings this to mind. Sometimes your subject can be the problem, like focusing on a bird sitting on a branch, hidden among other branches and leaves.

While the lens is what focuses, the camera body is what controls the shows. Sometimes the combination of focusing mode, AF point selection, and other settings can degrade performance.

You will get the fastest AF performance One Shot mode, which is what the Green [A] mode uses. One Shot mode gives you a focus lock confirmation beep, while AI Servo does not.

So, I ask what focus mode are you using? Which AF point(s) are you using?