Via the latest firmware update - http://av.jpn.support.panasonic.com/support/global/cs/dsc/download/fts/index.html
my Panasonic GX8 can now record a short burst of 4K video at different focus points which can then be selected frame by frame. There is an explanation of how it works in this excellent Mirrorlessons article here :- http://www.mirrorlessons.com/2015/11/25/panasonic-post-focus/
It's being called 'post focus' but in fact it's probably better described as selective focus since the camera is recording a series of video frames with different focus points at 30fps and allowing any or all of those frames to be selected as a still. You can do this in camera by scrolling through them using the touchscreen or since the video clip is recorded to the card you can also do this afterwards by doing a screen grab using software that allows that. The free VLC app. is one such programme. In some ways it's similar to the 4K photo function that allows an 8MP still to be 'grabbed' from moving footage. And like that Panasonic feature the frame can be set to 1:1, 4:3, 3:2 or 16:9 and still produce an 8MP file. It takes a while to complete it's run, so holding the camera steady while hand holding and choosing compositions that don't move about too much makes for the best results.
As you can see from the samples at the top of the page, it works well. It even managed to focus on the horse through the foliage to give me that option. Like both samples I used my lens, an Olympus 45mm f/1.8, wide open to get the most dramatic differences. So is this just yet another mirrorless gimmick, 'fun things to do with 4K video' or does it offer genuine creative and useful possibilities? Well, yes and yes would be my answer, but with reservations in the case of the latter. Yes to the first part because if you know your way around your camera, you can do what this does quicker, without having to 'throw away' all those pixels. I.e. Use all 20MP's instead of 8 on a GX8. And yes to the second part as well, because if you shoot in the specific way that makes use of it - wide apertures and with a subject that has some distance between the front and back of the frame, it can come up with some interesting compositions. I actually put together some pairs of images like the ones above and have uploaded them to a picture library offering a client a choice of focus point for the same composition.
There is however something strange going on regarding how the camera captures the video. That seems to involve a good deal of detail cancelling noise reduction. As you can see from the 100% blowup below, the captured image is none too sharp and in fact looks pretty much like a smartphone image with all the luminance noise (and detail) 'smoothed' away. As you can see that doesn't do a lot for the IQ and in fact it looks quite unpleasant blown up.
This somewhat spoils what is an interesting use of 4K. The problem seems to be in the footage as the clips produced are someway short of what I would expect from Panasonic 4K output. Now why Panasonic feel the need to do this, I cannot really say, but the resultant image looks very similar to a heavily noise reduced smartphone image.
So, for me, I suspect this is something I won't use a lot, if at all. There has to be a really good reason to accept this significant drop in quality and I certainly can't think of one at the moment. There is no doubt the technology works very well, but unlike the 4K photo function, which does actually produce decent files capable of a good size reproduction, I'm not sure that this does. So if you have a good reason to use it and you feel the quality is fine for what you do then fine. But I would assume that if you own and are using a GX8, the quality of the images you can create is important to you, I know it is for me and from what I see, I wouldn't be happy with these results for my stock photography work. My smartphones produce better than this.
Finally I can't help thinking that there are more important things that could have been added to a GX8 via firmware. A % battery readout for a start. File under nice try but no cigar!!