Panasonic GH4 Video Capabilities

A whole new level for video recording in compact ILCs

by Dave Etchells

The earlier GH3 was already one of the leading interchangeable-lens video platforms, but the Panasonic GH4 takes its video capabilities to a whole new level, with full 4K video, both IPB and All-I recording in a range of container formats, data rates as high as 200 Mbps(!), clean HDMI output at either 8 or 10 bits, and a super-high full HD frame rate of 96fps for 1/4x slow-motion when played back at 24fps. There's a whole host of other features, so many that we're going to just hit them briefly here. It's safe to say, though, that the Panasonic GH4 is a dream machine for both professional and high-end amateur videographers.

4K recording. Around the office, we've been joking that 4K is this year's 3D, given the massive focus on it at this year's CES show. TV manufacturers are clearly hoping that 4K will revive TV sales, by getting consumers to upgrade their current sets, just as they did with 3D. While 3D was an unmitigated flop with consumers, 4K does in fact bring noticeable improvements in image quality. Whether the improvements will be enough to make consumers reach for their wallets isn't clear, but 4K is potentially useful for many filmmakers, looking to integrate video with conventional film. Depending on the software involved, it's also quite possible that downsampled 4K video will result in better-looking HD than you'd get shooting directly in HD in the first place.

However the 4K space eventually sorts itself out, the Panasonic GH4 will be fully 4K capable at launch, able to record in both 3,840 x 2,160 and 4,096 x 2,160 formats, recording IPB data at a rate of 100Mbps in either format. (The processing burden of encoding 4K data means the data rate is limited to 100Mbps; the camera can do 200Mbps with conventional 1080 HD imagery.)

High bit rates, multiple container formats. We just alluded to this, but a key feature of the Panasonic GH4 is the very high data rates it can record at, as well as pass through its HDMI port (more on that in a bit). Where the GH3 was limited to a maximum of 50Mbps (not too shabby in its own right), the GH4 can go as high as 200Mbps in All-Intra mode at full HD resolutions, and frame rates from 24-60fps. IPB recording can go as high as 100Mbps, at the same frame rates. High bit rate video can be saved in either MP4 or MOV containers, and standard AVCHD format can be recorded up to 28Mbps. Of course, data rates of 200Mbps require a very fast memory card to keep up. The Panasonic GH4 is compatible with the SD UHS Speed Class 3 (U3) standard, which guarantees an uninterrupted 30 MB/sec data stream. Very few of these cards are on the market as yet, so be sure you're using the right card, if you want to achieve these very high sustained data rates.

Panasonic Lumix DMC-GH4 Video Options
4K
Container	Resolution	Frame Rate	Bitrate	Compression
MP4 / MOV	Cinema 4K (4,096 x 2,160)	24.00p	100Mbps	IPB
	4K Ultra HD (3,840 x 2,160)	29.97p / 23.98p
		25.00p
		24.00p
		29.97p / 23.98p
		23.98p
High-Bitrate Full HD
Container	Resolution	Frame Rate	Bitrate	Compression
MP4 / MOV	1080p (1,920 x 1,080)	59.94p / 50.00p	200Mbps	ALL-Intra
			100Mbps	IPB
			50Mbps
		29.97p / 25.00p	200Mbps	ALL-Intra
			100Mbps	IPB
			50Mbps
		24.00p	200Mbps	ALL-Intra
			100Mbps	IPB
			50Mbps
		23.98p	200Mbps	ALL-Intra
			100Mbps	IPB
			50Mbps
Low-Bitrate Full HD
Container	Resolution	Frame Rate	Bitrate	Compression
MP4 / MOV	1080p 1,920 x 1,080	59.94p / 50.00p	28Mbps	IPB
		29.97p / 25.00p	20Mbps
	720p (1,280 x 720)		10Mbps
	SD (640 x 480)		4Mbps
AVCHD Progressive	1080p 1,920 x 1,080	59.94p / 50.00p	28Mbps
AVCHD		59.94i / 50.00i	17Mbps
			24Mbps
		23.98p	24Mbps

Clean HDMI, 4:2:2, 8 or 10-bit output."Clean" HDMI means straight output of the video stream, without any viewfinder or settings overlays, for recording on an external recorder. So-called 4:2:2 is a standard professional digital video format, and is supported by most video-capable ILCs (Interchangeable-Lens Cameras). The big news with the Panasonic GH4 in this area is that you can select either 8 or 10-bit output. The higher bit-depth will produce much smoother gradations, something particularly noticeable in areas of very subtle variation, such as blue sky, or subtle highlight gradations. (It's important to note here, though, that the GH4's 10-bit output is only available when streaming video to an external recorder. The data recorded on the internal SD card is 4:2:0 at 8 bits, and internal recording is not supported when 10-bit HDMI output is active.)

Zebras! This was a very highly-requested feature from GH3 customers, and Panasonic stepped up to offer it in the GH4. It's a way of easily seeing areas of your image that might be over- or under-exposed; the camera overlays a pattern of zebra-stripes on such areas, making them immediately evident. For whatever reason, relatively few video-capable ILCs offer this feature, but it's a standard one in dedicated video equipment that pro video shooters rely on heavily.

Variable frame rate. Mentioned briefly above, this will be of interest to people wanting to shoot slow-motion video. Shooting slo-mo involves capturing video at a high frame rate, and then playing it back at a slower one, typically 24fps. With a maximum frame rate of 60fps, most video ILCs can only achieve only a 1/2.5x slow motion effect. The GH4 supports frame rates as high as 96fps at full HD resolution, meaning you can achieve a slow motion effect of 1/4x.

Time Code, Rec run/Free run. As the name suggests, time code is a separate data stream of precisely-encoded time information that indicates just when each frame of video was shot. Time code is essential for editing-together video shot on different cameras. Rec run means the time code advances only when the camera is recording, while Free run means it runs continuously from whenever it was first set. Free run is useful when multiple cameras are being used, with the video from each stopping and starting at random times. With the DMW-YAGH interface unit (the AF-YAGH outside the US, see below for more info), the Panasonic GH4 can also accept external time code input, so multiple cameras can be precisely synchronized on a set.

Pro-level video signal adjustments. This is a bit of a catch-all category, as there are a number of adjustments to the video signal that important in professional environments. Among them, the Master Pedestal Adjustment sets the black level of the video signal, Cinema-Like Gamma makes the GH4's tonal rendition match the specs of cinema vs normal video output, and Luminance Level Adjustment lets you set the tonal range from 16-255 brightness units, 16-235 units, or 0-255 units. While of little interest to amateurs, these adjustments are critical in professional applications.

Color bars and audio reference signal output. This is another pro-only consideration, but having the Panasonic GH4 able to output standard color bars and an audio reference signal makes it much easier to match its output to other video devices, avoiding odd color casts, tonal breaks, or audio level problems.

Center marker. This is a small point, but illustrates the attention Panasonic gave to user requests in designing the GH4. Having the frame's center point marked with an overlay in the viewfinder display can help a lot in setting up shots, especially when you need to match the framing from one take to another.

The DMW-YAGH Interface Unit (AF-YAGH outside the US). While the Panasonic GH4's video capabilities are quite impressive on its own, the DMW-YAGH interface unit delivers a lot of connectivity that's important to professional videographers. The shot above shows a rear view of it, where you can see separate stereo VU displays (the bar graph segments on the left), the manual record level adjustments for both channels, and the controls to set mono or stereo recording, and the level options (including +48v phantom power) for the two XLR connections on the side.

As the name "Interface Unit" suggests, the main function of the DMW-YAGH is to provide audio and video interfaces necessary for use in professional videography applications. On the audio side, a pair of latching XLR-type connectors provides balanced-line connectivity for external microphones, and as noted above, the unit is capable of accepting either line-level or mic-level signals, as well as providing +48v phantom power for condenser mics.

There's also a set of four BNC connectors for the SDI digital video interface preferred in pro video applications. A key advantage of SDI connections over HDMI ones is that the BNC connectors lock, so the cables won't disconnect if they're tugged. As alluded to earlier, there's also a time code input (TC In) connector, that lets you slave the Panasonic GH4 to a master clock that ties together all the capture devices used on a set.

The DMW-YAGH adds some bulk to the GH4, but really not much more than dictated by the bulk of the connections themselves. (They arguably might have reduced the bulk slightly, by having the SDI and XLR connections exit from opposite sides, but that would have resulted in much more unwieldy cable routing.) The combined package is still very much hand-holdable, although you'd probably mount the camera on a fluid-head tripod for most pro video applications, anyway.

At the time of this writing, Panasonic hadn't yet released prices for either the GH4 itself or the DMW-YAGH interface unit, but it's a safe bet that they'll come in well below the cost of current competing solutions from other manufactures. (For instance, we expect that the price of the Panasonic GH4 itself will be close to that of the GH3 before it, which will price it far below competing pro-grade 4K capture solutions.)

Update 03/10/2014: Panasonic has announced pricing and availability! Suggested list price for the DMC-GH4 body is US$1,699.99, a $400 premium over the GH3's list price. The DMW-YAGH interface unit is listed at US$1,999.99. When purchased together, the body plus interface unit go for about US$3,300. Shipments begin in late April, 2014.

Panasonic GH4 video summary. As we said at the outset, the GH3 was already one of the preeminent video capture platforms on the market, but the Panasonic GH4 represents a large step up in almost every area. After testing a full production unit, the GH4's video capabilities are indeed very impressive. The GH4's capabilities, at the relatively affordable pricepoint, should really throw down the gauntlet to all competing manufacturers. Hard on them, perhaps, but a very good thing for videographers everywhere.

 

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