autofocus HVX

Cees Mutsaers

Cees Mutsaers

Veteran
I still do not read if the HVX has a real autofocus system (like the Z1) and not only a focus assist where you have to fine tune manual to the point of focus.
 
It does have auto focus, but because it's slower in 24p and 30p based on the sample rate, they call it focus assist. The autofocus in 1080i should be as good as any other autofocus.
 
why does does the autofocus speed depend on the sample rate in 24p and 30p mode? Is it any good in those modes (not to slow)?
 
You don't really want to use autofocus in 30p or 24p--at least on the DVX. I'm guessing it won't be THAT much better on the HVX--not an issue for most of us anyway though, I think.
 
Cees Mutsaers said:
why does does the autofocus speed depend on the sample rate in 24p and 30p mode? Is it any good in those modes (not to slow)?
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From my limited understanding, it has something to do with sample rate of the CCD's. The auto focus samples the image and adjust accordingly, since the CCD is 50% or 40% of 60fps when in progressive, fewer samples equals slower response time.

Correct me if I'm wrong anyone.
 
rbilsbor said:
You don't really want to use autofocus in 30p or 24p--at least on the DVX. I'm guessing it won't be THAT much better on the HVX--not an issue for most of us anyway though, I think.
Click to expand...

Why not? I have used focus assist and have no problems with it. I prefer manual most of the time.
 
The faster the frame rate, the more responsive autofocus will be. Autofocus in 720/60p would be just as fast as it would be in 1080/60i. Autofocus in 720/12p will be very, very slow. The autofocus system's accuracy and responsiveness increases in relation to the # of updates it gets.
 
None of these cameras have LCD screens that display the full pixel resolution of the frame. That's why they all offer some sort of focus aid.

The HVX's seems the most useful, in that it offers regular peaking and it also offers an expanded focus which gives you a 1:1 pixel extraction window on the screen. It's like the Sony implementation except that the Sony only allows for focus assist when you're not recording; the HVX allows for it even when recording so you can use it for a rack focus etc.
 
For me the best focus assit is on the JVCproHD camera. It shows you were the focus is by putting a blue line on the part of the picture that is in focus. Like if you film an interview you know if the focus is on the nose or the ears. I tried it and it was amazing! And in HD, focus is very VERY important!
But I will still buy the HVX because of the slowmotion capacity in DVCPROHD that no other camera has.
 
The JVC's focus assist works in some circumstances, and works very well. In other circumstances it's completely useless. It doesn't function in low light at all, for example, or if there are no sharp edges to accentuate. When it does work, it works very very well. But if it can't latch onto some high-frequency detail to illuminate, well, you're on your own because the LCD itself isn't very high resolution.

The Sony and Canon both offer the zoom-in method, which works no matter what the light conditions, but it can make framing tricky and the Sony's is completely useless in a "I need to grab focus quick" type of scenario, because it doesn't work while the camera is rolling! So it can be very helpful to use to set up focus before shooting, but once you hit "record", the Sony has basically *no* focus assist method. Not sure about the Canon, I didn't test whether it works when recording or not -- I think it probably does, because they added some yellow "focus assist" words in the middle of the LCD to remind you that the feature's active. But while it's active you only see the center of the frame, so you can't focus and maintain accurate framing. JVC's method at least lets you maintain an accurate frame when you're using the focus assist feature.
 
I though I heard somewhere that the HVX implementation of the "zoom in" focus assist fills only the center of the frame, allowing "normal" framing on the borders. If true, this is terrific, as you could still keep your shot framed while the center of the image at 1:1 allows for critical focus...

Jim Arthurs
 
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