Though it feels like a long time since Panasonic released the Lumix DMC-GH3, in truth it's only been a year and a half; it's the rate of technology change in that camera's cohort that makes it seem an eon. But it looks like what we're getting might have been worth the wait. The GH3's successor, the Lumix DMC-GH4, packs a host of feature and technology enhancements in the old body that offers something for everyone: 4K video and a new autofocus system with improved continuous-shooting performance are just the highlights.
For all the combinations of video frame rates, bit rates, audio formats, and file formats this camera is capable of shooting, you'll have to consult Panasonic's site: I think there are 36, not including the options for new variable-frame-rate (0.25x to 4x) HD video. It's the first prosumer model to offer Cinema 4K (C4K, 4096 x 2160) as well as Quad HD 4K (QHD, 3840 x 2160), and notably it supports potentially extra-high-quality HD, meaning 4:2:2 10-bit output with a 200Mbps bit rate at all the major frame rates. It also adds a higher-quality All-I codec in addition to interframe compression, though it doesn't support All-I for either 4K standard. Unlike the GH3, the GH4 supports multinational video standards in one camera. Other new video-related features include colour and audio reference signals, Zebra, and a 15-step master pedestal setting.
The Interface Unit.
(Credit: Lori Grunin/CNET)
Note that you can't just pick up the camera, stick a card in, and shoot best-quality 4K. In-camera you can only record 4:2:0/8-bit video; to record 4:2:2/10-bit video you to need run it through the HDMI connector to an external recorder via the horribly named, but practical, Interface Unit (DMW-YAGH), a powered dock that adds two XLR inputs with audio controls, SDI output, and various time-code options. To record any video at 100Mbps or higher in-camera, you need a UHS Class 3 (U3)-rated SD card for a minimum sustained write speed of 30MBps. (I do wish there were two slots.) However, none of these are drawbacks so much as technological facts of life at the moment. On the upside, you'll be able to start small — though not even that small — and grow into the camera by accessorising. Speaking of accessories, Panasonic also announced a shotgun mic and support for some zoom mic features in the camera to go along with it.
To support 4K, Panasonic had to incorporate a new sensor (albeit at the same old resolution) with a faster readout rate — in this case half that of the GH3's sensor. In conjunction with the latest iteration of its Venus Engine image-processing chip, Panasonic claims a wider dynamic range and decreased rolling shutter.
While it uses the same metering system as earlier models like the GX7, the GH4 debuts a new autofocus system, a combination of traditional contrast AF and DFD, or Depth from Defocus. In theory, when the camera knows the characteristics of the lens and the deviation-from-focus of two planes parallel to the focal plane, it can calculate the location of the in-focus area faster than it can iterate there using plain old contrast AF (the contrast AF system has been enhanced as well, though). So it uses DFD to make the rough calculation and then fine-tunes it with contrast AF. In Panasonic's demos, it looks pretty fast. Too fast, in fact, for video, where you don't want it to snap from one subject to another; you want it to glide gracefully between the two. It remains to be seen if there are any controls over the focus speed for that.
The design and control layout are nearly identical to the GH3's, with a few exceptions. The mode dial now locks; it has a larger, more comfortable eyecup on the viewfinder; and the EVF and LCD are higher-resolution, and Panasonic claims better colour reproduction and less distortion for the EVF. It remains weather-sealed, with a die-cast magnesium-alloy chassis, but the shutter durability rating has been upped to 200,000 cycles. Lastly, the Wi-Fi connectivity now can use NFC and QR codes to more quickly pair devices.