Auto-focus is faster in 50i recording mode

G

Gugulino

Active member
I saw in the manual that only in 50i or 60i you get fast auto focus. I tested it with my Panasonic 14-140 mm lens and it seems true. Has anybody else made this experience?
In fact, there is written that also 50p and 60p is also capable of fast auto focusing. These frame rates you can only get with VFR and then auto focus is disabled. So, does anybody know what this should mean?
 
Autofocus always performs better with a faster frame rate. It has always been that way. 720/60p autofocus performance is much, much, much better than 720/24p. 1080/60i autofocus is much, much better than 1080/24p.

In fact, when the original DVX100 was introduced, they disabled autofocus in 24p because the performance was so slow. People screamed and demanded that it be enabled, so in the DVX100A they enabled it, but they wouldn't call it "autofocus", they instead called it "focus assist". And then people started complaining that it was too slow to update. Well, of course it is! The system is feeding updates to the processor at only about 40% the speed it would be in 60i.

If you want the best autofocus performance, you need to use the fastest frame rate possible.

But VFR is not an option, because enabling VFR disables autofocus entirely.
 
Thank you for this nice explanation! So, 50p and 60p was related to 720 resolution. I forgot that. I think for shooting an event like a Musical I should use 720/50p, because I need a fast auto focus and the end product is only a DVD.
 
I think that they are assuming that you are letting the camera control the shutter speed. I think the faster the shutter speed the better the auto focus. Therefore if you use 1080p @ 24 FPS the camera will choose a slower shutter speed than if you use 720p @ 60 FPS.
 
For a PAL DVD, 720/50p would definitely make an excellent source.

The issue isn't about shutter speed, it's about how frequently the autofocus system receives updates. At 60p it's receiving 60 updates every second, at 30p it's receiving only 30 updates, at 24p it's receiving only 24 updates. When autofocus is "hunting", trying to find the best spot, that makes a huge difference in its response speed. Faster updates = quicker locking-on.
 
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