Autofocus: 720p60p VS 720p30pn

F

filmguy123

Veteran
is shooting at 60fps in 720p any faster for autofocus than shooting 30pn?

Is 1080i AF faster than 720p?

All I know is, 480i60i is faster than 480i30p... so wondering how it breaks out for AF speed in the HD modes??

Thanks!
 
OK, so whether the BASE is interlaced or progessive does not matter - just that I am capturing 60 frames (or fields) a second is the important part?

Does setting the shutter to 1/30 (vs 1/60) affect the speed of the auto focus? I am going to be shooting in a semi low-light area for a wedding reception and trying to figure out the best way to do it, as I can't add any external lighting... Perhaps 720/60p with 1/30 shutter? Would that still get me somewhat speedy AF with the iris all the way open?
 
What matters is what speed the sensor is running at. If it's running at 60fps, it's feeding the autofocus system sixty updates per second -- lots of information, for fine-tuning and quick changes. But if you slow down the frame rate to 24 fps, then the autofocus system only gets updates 40% as often, leaving a lot more room for error and slow response.

Yes, setting the shutter to 1/30 will (I think) cut the autofocus speed in half, as well as cut the frame rate in half. 720/30p @ 1/30th will be as fast as 720/30p @ 1/60th, but 720/60p @ 1/30th will be the same as 720/30p @ 1/30th.

Fastest autofocus will be 720/60p @ 1/60th, and then put on some gain if you need more brightness. But autofocus doesn't perform all that well in low-light conditions, so you should recognize that you're starting out with some of the cards in the deck stacked against you.
 
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