Lens "Breathing" in Autofocus with Lumix 14-140

[Rbrookler]

Just acquired a used AF100 and Lumix G Vario 14-140 Lens. In Auto Focus mode, I'm getting a strange bulging back and forth in the frame -- as though the lens is breathing in and out -- when there's movement in the shot. The problem disappears as soon as I switch to Manual Focus.

Here's a link to a brief video sample: wobble sample - YouTube

I'd be grateful for any insights into this? Thanks!

P.S.
Iris is in manual
1080/60i
Face Detect and Face Framing have no effect on the problem whether on or off
OIS has no effect on problem whether on or off

[bengiles]

Err... it's the lens auto-focusing?..

I personally cannot comprehend why anyone would operate an AF100 in auto-focus, but I'm guessing your 14-140 is simply trying to lock focus and it's a lens that will "breathe" when changing focal distance - I guess what you are seeing is the camera's efforts to hunt for something to focus on. The books behind represent a fairly easy contrast ratio to lock onto, but the foreground movement will confuse the fairly basic auto-focus, especially with the lack of any discernible lighting.

If you have to shoot yourself solo, I'd hazard a guess that you might get quicker and easier results with a domestic camcorder that is designed purely for auto-focus.

Ben.

[BrandonT]

I believe you have OIS (optical image stabilization) turned on. You never want this on when the camera is locked off or else you'll get a weird effect. I used my 14 - 42 handheld in autofocus on Wednesday and it performed quite well. I have to imagine that the 14 - 140 would be better since it's supposed to be "the" lens that has been optimized for video. But I haven't used it myself. Also, you can set a region using the function button that you want it to autofocus on. And there's also face tracking. I haven't tried it all myself, but I've had the camera less than a week. If you have Barry's book, he lays it out pretty well.

[Rbrookler]

Thanks. I did try both OIS and Face Detection/Face Framing on and off, and this did not eliminate the problem. It was also my understanding that the 14-140 was the best lens for Auto Focus. I don't actually plan to use Auto Focus all that much, but since it is a pre-owned camera/lens I wondered whether this "breathing" effect was normal or a function of some setting ... or possibly a problem with the camera/lens.

[BrandonT]

Hmm. I don't know, then. Do you have another autofocus lens you could check? Did you turn autofocus off and it stopped?

[Rbrookler]

Yes, changing to manual focus eliminated the problem. It's definitely related to the auto focus. (And I did disconnect and reconnect the lens. And I did do the firmware upgrade.)

I don't own another lumix auto focus lens, but I can rent one. That would be my next step unless anyone on the Forum knows this "breathing" effect to be normal for AF.

[XSVpro]

As Ben said, this is just the camera/lens trying to find something to lock on to with auto focus, the 14-140 does breath when finding focus.

I don't think anything is wrong with it but it should focus on something pretty easily, if its constantly trying to get focus and never does/is erratic, it could mean the lens has been dropped.

Personally I think its just an over reaction to the auto focus mechanism, don't worry about it and leave it switched off ;0)

[Rbrookler]

The focus position does flutter for a bit, but it does stabilize within a few seconds. And it remains stable until there's some significant movement. So I guess it's operating properly. Many thanks for everyone's help.

[Gugulino]

The new 35-100 mm lens from Panasonic shows the same breathing when in auto-focus. What I also noticed on the 35-100 mm that when you change the focus plane it substantially alters the focal distance. I thought that with this lens these issues have gone.

[electricpig]

It's just center weighted auto focus. He moves through the center of the frame,
it refocuses slightly towards the books as the plane is changing, then he comes back across, it refocuses, etc.

Manual focus, no problem.