Ok, I read earlier threads on focus pulsing and thought they were wacko.

But I had it happen to me this week. I was shooting a long shot of boats at infinity, ois on, probably af on, not zooming. First couple seconds of this one shot are fine, then it goes into a rapid (i'm guessing, but maybe 4x per second) in-and-out of focus pulsing. Much faster than the af works.

I was shooting similar shots all day, both before and after, and it only happened for this one shot, and not for the whole shot.

Anyone else have this happen? I'm wondering if it could be rf inteference from a cell phone or a motor?

You didn't mention your shooting mode. Was it 24F?

It was 1080i60 when it happened.

It was 1080i60 when it happened.

This is just the way Canon camera focus behave, it is not very good, you just have to accept it or learn how to use manual focus, what happen is that it couldn't decide what to focus on, it might lock onto something but then it see something else with more contrast and switch to it or you are right on the edge of the focusing area and it switch back and forth, or it could be that you have the IF on at the same time as auto focus, the IF beam might hit on something in the foreground but the auto focus (base on contrast and vertical lines) might see something else in the background and the system couldn't decide what to focus on and so it hunt. The best is to learn to manual focus, if not then I would turn off the IF and use only auto, and use push button AF when needed.

Hi Chuck, I have had this same thing happen to me. I believe it is just the Auto Focus trying to chose the subject. Much like what Khoi said. I would recommend using manual focus anyways.

Best of luck!
~Gabriel

i had this happen to me this week--but I had my A1 on manual focus. It has some weird pulsing issues. Fairly minor, and it's at the edge of the frame. I'm shooting at 60i. I don't think it's in every shot--don't know yet. I haven't tested it too thoroughly.

It seems much too rapid to be af hunting. It's very unlike any af issue I've seen before.

Is this happening when the Instant AF feature is on? If so, that could account for the rapid hunting.

For me, no. I'll post a short clip as soon as i get back in my editing room. no af, no iaf.

I seem to recall that I was able to create the effect with IAF on and off. Now I definitely have not been able to create the pulsing with AF completely off.