I was shooting some video with my Panasonic G2 this evening. I had the camera in Single Shot AF mode. I half depressed the shutter button to activate the focus on a far away subject, thinking that the focus would be locked at that point, and then pressed the movie record button to start video recording. Then the whole scene went out of focus and then came back into focus....it also did this same thing again later during the recording – like it was searching for focus. Basically, it was behaving like it was in Continous AF mode.
I spent a day at the zoo filming video last year using Single Shot AF on my G2 and it never behaved like that then. Obviously with Single Shot AF, it should focus just once (with a half press of the shutter button) on whatever subject you select and stay locked at that distance.
I guess in future, after half pressing the shutter button, I can quickly switch to manual focus mode and hope that the previous focus setting will be retained. It will slow me down a bit when trying to film things in a hurry it'll just have to do.
For those who shoot with the higher end models like the G6, GX7, GH3 etc, have you ever experienced the camera hunting for focus during video recording with Single Shot AF enabled? I'm considering purchasing one, or more, of these cameras for wedding videos and I hope I don't have to switch back and forth between auto focus and manual focus modes every minute or every few seconds for fear that the auto focus is going to behave erratically. I know that many of you are going to say: "Just use manual focus and you'll be fine." I used to use old, manual focus film gear exclusively but I don't think my eyes are as good as they used to be. Plus I like that auto focus is super quick and I can choose which part of the scene it can focus on. Though my only concern now is if it can stay locked on where I want it.