Focus problem - is this a fault in the G7 camera

JakeJY wrote:

Brisn5757 wrote:

I took a look at some of my video clips that had the focusing problem and most of the time the subject goes out of focus during zooming while video recording. There are two ways the camera goes out of focus.

1. Focusing while zooming in/out. So one frame will be in focus and the next frame id out-of-fous etc.

2. refocusing after I have zoomed in/out. This is a problem as it can be out of focus for a second or two before it finds the correct focus.

This information is fairly critical and glad you mentioned it. In this case this is likely normal behavior. This lens is not a true parfocal lens (meaning it doesn't maintain focus during zooming). Panasonic cameras however do "simulate" parfocal in software, but this means the lens has to refocus while you are zooming to try to maintain focus on the subject. It may not always get it right.

The aperture you set it at may matter too depending on how the lens is designed (how the variable max aperture changes). For example setting it at f/5.6 or smaller may help (or it may make it worse than setting at f/3.5 so it is always wide open).

But there are time when I have not zoomed when it goes out of focus, maybe the camera needs to recheck the focus at times. In one case a person held up a card that appeared in center of the frame causing the camera to refocus yet before then someone had moved around the room and the camera dd not go out of focus.

The G7 camera currently has the following setting for video:

AFS/AFF set to AFS

Continuous AF = ON

Metering mode = Focus and measure subject on the center of the screen

MP4 28M/50fps

Brian

This behavior likely has to do with two factors. Given you set focus to center, then the change in the center triggers a refocusing and by holding up a card, the focus plane changed.

In the second case, the person moving around the room may not have moved over the center focus area or even if they did, they may have stayed on the same focus plane (moving across the frame, rather than toward or away from camera).

Thanks for your feedback JackIY.

In the case of the parade I video recorded it was a dull overcast day and from the stills I took while recording the aperture was mostly f3.5 with a shutter speed of 1/250.

In the case of the card that might have caused the camera to refocus. The person was at one stage moving towards the audience and closer to the camera than the card was and there were people standing near by behind the card he had in his hand. But a chance in focal point was worth considering. It may also depend on how long the person is close to the camera before the camera decides to refocus.

Brian