Sony RX100 Autofocus Jitter/ Pulsing in Movie Mode

Started Jul 21, 2012 | Discussions thread
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Re: Sony RX100 Autofocus Jitter/ Pulsing in Movie Mode
In reply to On the Fence, Jul 22, 2012

I can see it in this one. I think its just the AF racking in and out to adjust to the scene.

AF works by actually changing the focal length slightly (its known as focus breathing), which is what the camera is doing as that person is walking by. Its most obvious at the periphery because thats where you see the slight change in focal length. I bet its worse at longer focal lengths too.

On the Fence wrote:

I just tried watching this same clip on my laptop -- it's much harder to see. So clearly this effect is more or less obvious depending on screen. What I'm seeing is a high frequency jitter combined with a low frequency pulse. Depending on how your screen renders motion, it may well be nearly invisible, or unacceptably obvious.

Here's another clip with more prominent jittering:

Once again, focus your attention on the upper left quadrant -- the magazine rack is a good spot. You should be able to see low-frequency pulsing, as if the lens is very slightly zooming in and out, which is probably a consequence of autofocus tracking.

Along with this, you should be able to see a high frequency jitter, which I'm going to speculate is due to lens elements vibrating as the autofocus tracks.

Once again, I'd recommend downloading the original MTS clip and watching on a 1080 screen at a fairly close viewing distance. Once you spot it, it's becomes a lot easier to see.

The jitter looks very much like wind blowing on a tripod--though there's obviously no wind inside my apartment.

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