Auto Focus

[Steve Lewis]

I have had problems with auto focus (especially IAF) and I was wondering if you guys have had similar issues. When I zoom in on an object or person, it seems to take quite a long time to focus and it usually stays completely out of focus until it sort of snaps quickly back into focus. My PD170 was usually very good at staying in focus even while zooming... Also, do you prefer normal or instant AF?
Thanks,
-Steve

[Nate Haustein]

Make sure your IAF sensor isn't being covered up- I've had really good luck with mine lately, just that one point in the zoom when focus breaks for just a second. Only problems I've ever had were when i was at almost full telephoto.

Sorry to hear you're having trouble, one of my main reasons for switching to an XH was the inconsistent focusing on my GL2; I know what a pain it can be.

[Chris Soucy]

The A1 can either zoom or focus, not both at the same time.

If you want an object to stay in focus during a zoom, first zoom right in to Z99, focus, turn off IAF, zoom out to your chosen start point and fire away.

The A1 will now hold focus all the way back in to Z99.

If you leave IAF turned on, there is a good chance the focus will decide to "hunt" either at your chosen start point or when zoomed back in to your end point.

If you dive into the menu's and turn on "grids", you will find that the AF system can't be relied upon to get focus properly until the central "box" (or another similar sized portion of the field of view) is almost filled with the object, depending on contrast, verticals and a host of other things.

Once you've mastered that, focus becomes a doddle.


CS

[Jonathan Schwartz]

Steve,

The frame rate you chose also has an effect on this. At 24f it takes much longer for the camera to auto focus than at 60i. I have no idea why, but when I film marching band events, I make sure to use 60i because it autofocuses so much faster.

Jon Schwartz
CA Video Productions

[Philip Williams]

Originally Posted by Jonathan Schwartz

Steve,

The frame rate you chose also has an effect on this. At 24f it takes much longer for the camera to auto focus than at 60i. I have no idea why, but when I film marching band events, I make sure to use 60i because it autofocuses so much faster.

Jon Schwartz
CA Video Productions

The focus sensor gets samples at the same rate that your video is shot at. So 60i gives you 60 samples per second, providing a lot of data for the autofocus mechanism. At 24F you're only getting 24 samples per second, so autofocus becomes quite a bit slower.

This is a known issue with pretty much all 24P cameras. A good reason to get really good with manual focus ;)

[Jack Walker]

Originally Posted by Philip Williams

The focus sensor gets samples at the same rate that your video is shot at. So 60i gives you 60 samples per second, providing a lot of data for the autofocus mechanism. At 24F you're only getting 24 samples per second, so autofocus becomes quite a bit slower.

This is a known issue with pretty much all 24P cameras. A good reason to get really good with manual focus ;)

Would it be possible to double or triple the autofocus sampling rate over the frame rate in a camera like the XH-A1?

Is this a firmware or a hardware issue?

The autofocus on the XH-A1 at 60i can be stunning, whereas at 24F it is disappointing.

[Philip Williams]

Originally Posted by Jack Walker

Would it be possible to double or triple the autofocus sampling rate over the frame rate in a camera like the XH-A1?

Is this a firmware or a hardware issue?

The autofocus on the XH-A1 at 60i can be stunning, whereas at 24F it is disappointing.

It just gets data whenever a frame is processed, so the focus speed is pretty much tied to the framerate. Its just the way the hardware is designed, and again, this is common to all 24P camcorders. The rule of thumb seems to be that most videographers use manual focus on 24P camcorders.

There might be some cams with different systems, but none that I can name off the top of my head.