Panasonic Lumix DMC-GH4: a quick summary
Please note that the camera pictured in this article is a pre-production model that is not 100% cosmetically final (for example, it is missing the 'GH4' stencil on the front plate).
From a hardware point of view, the GH4 looks a lot like the GH3 - and they're similar enough in footprint that the forthcoming model can still use the same external battery grip as the GH3. Some of the fine detail has been changed, with the inclusion of a 1024x768 (2360k dot) OLED viewfinder panel and a shutter that's capable of operating at 1/8000th of a second and rated to last for around 200,000 exposures (twice as long as the GH3's).
Under the familiar skin, a lot else is going on. It's probably fair to say that the bulk of the camera's improvements will be most apparent to video shooters, but there are also some extra features added for the stills photographers that Panasonic says are equally important to them in the GH4. Based on our briefing and an afternoon spent with a pre-production GH4, we've summarized the changes we've seen from both a movie and a stills-shooting perspective.
The headline feature is that the GH4 can shoot 4K video, capturing either Quad HD (3840 x 2160) at up to 29.97p or 'Cinema 4K' (4096 x 2160) at up to 24p. But 1080 fans aren't left out, either - the GH4 can capture Full HD footage at extremely high bitrates - with the choice of 200, 100 or 50Mbps at a variety of frame rates and in the choice of MOV or MP4 wrapper. That 200Mbps figure is based on using All-I compression (where each frame is treated separately during compression), while the lower option uses the more common IPB system (where the differences between frames are used to describe some frames).
In both Full HD and 4K video, the GH4 can be switched between capture frequencies (rather than previous models, which were pre-set, per-region). The GH4 provides three options: NTSC (offering frame rates of 23.98, 29.97 and 59.94), PAL (25 and 50) and Cinema (24) and requires that the camera be rebooted to switch between settings. It means that a single unit can be used to create content for a wide variety of applications and broadcast markets.
Movie shooting options (MOV or MP4 wrapper)
|59.94Hz||4K (3840 x 2160)||29.97p||100Mbps (IPB)||Linear PCM/AAC*|
|23.98p||100Mbps (IPB)||Linear PCM|
|Full HD (1920 x 1080)||59.94p||200Mbps (All-I)
|50.00Hz||4K (3840 x 2160)||25p||100Mbps (IPB)||Linear PCM|
|Full HD (1920 x 1080)||50p||200Mbps (All-I)
|24.00Hz||Cinema 4K (4096 x 2160)||24p||100Mbps (IPB)||Linear PCM|
|4K (3840 x 2160)||24p||100Mbps (IPB)||Linear PCM|
|Full HD (1920 x 1080)||24p||200Mbps (All-I)
*MP4 only. The MP4 option also includes several lower bitrate options, in addtion to 720p and 480p resolutions. AVCHD Progressive and AVCHD are also offered, limited by the maximum frame- and bit-rates of the two standards
In addition, the GH4 builds on the GH3's spec for videographers. Not only does it gain zebra and focus peaking, to guide exposure and focus when capturing footage, it also gains much called-for options such as a flatter, 'Cinema-like' gamma setting, Master Pedestal (black-level) adjustment and the ability to specify the scale used for luminance (16-255, 16-235 or 0-255). In addition to this, faster readout from the sensor should mean less rolling shutter.
The GH4's HDMI 1.4a connector allows it to output 4K or 1080 streams. The bit-rate and amount of color information (expressed using the '4:X:X' terminology of chroma subsampling) varies, depending on how the camera is used. By default, the HDMI outputs 8-bit 4:2:2, either for monitoring or for sending to an external recorder, leaving you with the option of using the 8-bit 4:2:0 files from the camera as more convenient proxies during the editing process. Alternatively, if you take the SD card out of the camera, you can use the GH4 as a camera head - which gives you access to a 10-bit 4:2:2 stream.
The camera is designed to use SDHC and SDXC cards with a UHS I bus (rather than the newer, UHS II format used in the Fujifilm X-T1), and Panasonic only promises the camera's full capability when used with cards conforming to the U3 speed class, which guarantees 30MB/s (240Mbps) sustained write speeds.
|The optional DMW-YAGH 'Interface Unit' provides a more extensive selection of video industry connectors for using the GH4 as part of a high-end video rig.|
An optional 'Interface Unit' (called DMW-YAGH, when sold through consumer channels), provides XLR inputs for audio and an SDI input for externally-generated timecode, along with four HD-SDI connectors for 4:2:2 10-bit output. It also provides a 12V DC power socket.
The base stills specification of the GH4 is very similar to that of the GH3, as it's still based around a 16MP Four Thirds sensor (although it should be noted that Panasonic touts it as being new and promises an extra 1/3EV of dynamic range at base ISO). The more powerful processor has encouraged Panasonic to raise the highest standard ISO setting to 25,600, while the new shutter mechanism sees the flash sync speed jump to 1/250th, up from 1/160th. A combination of those two additions helps double the camera's continuous shooting rate, to 12fps for up to 50 Raw+JPEG images, or 7fps with focus tracking.
Stills shooters will get some benefit from the camera's video upgrades - particularly in that they gain focus peaking, for fast manual focusing.
|With the exception of the locking mode dial, the handling of the GH4 is little-changed from that of the GH3.|
Probably the biggest change is a feature called DFD (Depth-From-Defocus) autofocus, where the camera uses image blur to judge subject distance. During live view (before a half-press of the shutter button), the camera will occasionally make a tiny adjustment to focus, to check whether subjects in the frame are in front of or behind the current focus point. In addition to this information, the camera judges how far out-of-focus objects in the scene are, based on how blurred they are, assessed using a profile detailing the blur behavior of the lens at its current aperture. Although this combination of data itself doesn't give the GH4 enough information to achieve precise focus, it does give it a clear idea of where it should start using conventional contrast detection AF process to achieve fine focus.
For now the camera will only have profiles for the company's 22 Micro Four Thirds lenses - meaning any DFD speed benefits will only apply to them. However, the company seemed to suggest the blur characteristics of other lenses could be included as built-in profiles in future Micro Four Thirds lenses from other makers.
Panasonic has said it won't be announcing pricing of the GH4 until near its (also unspecified) availability date. Despite the pro-level videography features, the company continues to describe it as a hybrid, consumer-accessible model, so while we wouldn't be surprised to see a price increase over the GH3, we don't expect it to cost vastly more than its predecessor.
|It's good to be at home by Nightcrawler12|
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