Helping the autofocus do its job faster

M

Malcolm Wright

Well-known member
Hi all,

This might be a very short thread, but I thought it deserved its own space.
I of course noticed the sluggishness of the autofocus very quickly after getting my HVX. That was a month and a half ago, and since then, Barry has explained that the frame rate you shoot at influences the responsiveness of the AF. The less fps, the less responsive.

I'm looking for ways to enhance this performance. I'm going to do some tests of my own, but perhaps Barry knows this offhand: does it make a difference whether you shoot 24p or 24pn for the AF? If in 24p we are recording the full 60 frames with a pulldown, does this mean the camera has 60 frames with which to do its AF magic, causing better performance? I'm certainly willing to take the p2 space hit on shots where I need the AF to perform better!

Are there any other tricks?

Thanks for your time everyone!

M.
 
Makes no difference. The CCD runs at the 24hz frame rate in both cases; it's just that the codec is fed duplicate frames.

The main trick is to eyeball the distance, guess what the distance is, and spin the focus ring to approximately that distance, and then let AF tune it from there.

But there's no getting around the fact that for best AF performance, it needs the fastest refresh rate it can get. 24P is not a good match for autofocus.
 
Barry_Green said:
Makes no difference. The CCD runs at the 24hz frame rate in both cases; it's just that the codec is fed duplicate frames.

The main trick is to eyeball the distance, guess what the distance is, and spin the focus ring to approximately that distance, and then let AF tune it from there.

But there's no getting around the fact that for best AF performance, it needs the fastest refresh rate it can get. 24P is not a good match for autofocus.
Click to expand...

Thanks Barry...

Its good to know that manually getting to the ballpark helps the AF... I'll give that a go!

M.
 
So you can use Auto-Focus in all shooting modes? If so that's a bit of a surprise because my DVX automatically switches everything manual on the DVX.
 
Yes you can use it in all modes. However, its degree of usefulness diminishes in direct relationship to how slow the frame rate is. At 60p/60i it works well, at 24p it's marginally useful.
 
Barry_Green said:
Yes you can use it in all modes. However, its degree of usefulness diminishes in direct relationship to how slow the frame rate is. At 60p/60i it works well, at 24p it's marginally useful.
Click to expand...

Ah, good job I'm now used to doing everything manual thanks to my trusty DVX! Can't believe how good I am at manually zooming, focusing and opening/closing iris now. Sometimes when I look back at the footage I think, how the hell did I manage to do that :)

I think that's what you get for being made to shoot with manual focus.
 
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