Focusing issues on EF-L 70-200 f2.8 ii

[Steve6696]

Hi

I am having focusing issues using the above lens. 

I use it mainly at marathons, so I'm focusing on a runner about 50 feet away, typically taking 3 shots in burst mode and AF-C focusing. I then move to the next runner however the camera refuses to focus. At this point if I then focus on the ground near to me it will focus and then when I re focus on the next runner 50 feet away it will focus correctly again. However it won't focus for the runner after that until I once again refocus on the ground in front of me. (Hope that makes sense!) 

Its definitely a new issue with the lens as I've tried it on my 2 bodies with the same outcome.

Its not an issue with my technique using the lens as it hasn't happened on the half a million shots previously using that lens. 

I've cleaned the contacts on lens and bodies and the screws on the lens are not loose. 

Any suggestions on what's wrong or anything else I can try before looking at a repair gratefully received. 

Thanks, Steve

[Waddizzle]

What camera bodies are you using?  I am not aware of any Canon camera bodies that have an “AF-C” autofocus mode.  Lenses do not focus, the camera body controls the focusing.

If you are using a Canon lens adapted to another brand of camera body, then I will not be of much help to you with your camera issues.

[Steve6696]

I meant AI Servo 👍

[Steve6696]

1D3 and a 7D2

[deebatman316]

When you say 1D 3 do you mean the APS-H 1D Mark III, Full Frame 1DS Mark III or the new Full Frame 1DX Mark III. Your cameras require contrast to focus. So if there's little to no contrast it won't focus. What happens with the camera set to One Shot AF. With a stationary subject will it focus. Is this the only lens with the AF problem.

[Steve6696]

It's the Canon 1DMark3. Been using them for 15 years specifically for my running photography. It's not the body that's the issue (unfortunately) as the problem occurs on my back up body as well, and only with this lens. Plenty of contrast for the camera to pick up and no issues after swapping to my Canon 70-200 f4L and Canon 24-105 f4L for races at the weekend. 

[Waddizzle]

If you wish to change tracking to a new subject, then you must let the camera know that is what you want to do.  For both of those bodies you will need to briefly stop or pause the AF systems, and then acquire your new subject.

I used to use the [AF-ON] button for BBF.  But I have found it much more useful to use it for [AF-OFF].  If lose tracking on a subject or want to acquire a new subject, then I just give the button a brief tap.  The AF system will restart using your previously defined “Initial AF Starting Point”, which for me is always the center AF point.

[Steve6696]

Thanks, yes for what I'm doing (15000 shots per race) any form of BBF would kill my thumb (as I found out early on) so I leave it off for this type of work. So shutter button does it all. This body/lens combo has worked well together for years until this weekend. 

[Waddizzle]

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@Steve6696 wrote:

Thanks, yes for what I'm doing (15000 shots per race) any form of BBF would kill my thumb (as I found out early on) so I leave it off for this type of work. So shutter button does it all. This body/lens combo has worked well together for years until this weekend. 

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I was suggesting that you try setting up BBF for [AF-OFF].  

You need to force the camera acquire the subject you want.  It will not do it for you.

[wq9nsc]

Steve,

That is definitely an unusual problem since it is occurring on two different bodies with the same lens.  Try toggling the AF distance limiter on the lens and then put it back in the desired position.  I suspect if contamination got into that area, it could create interesting responses from the lens since instead of the combination of open and closed contacts the camera expects it would also report one or more with resistance less than infinity but far greater than a dead short.

As an experiment, instead of shooting at the ground to get it to focus again just wait a few seconds and shoot another object at basically the same distance as the first.  Although the 70-200 f2.8 doesn't have the ring of AF stop buttons of its bigger L series prime and telephoto siblings, on rare occasion after using the AF stop buttons on the lens I have had my L series telephoto primes pause for a moment before AF is resumed.

Rodger