4K video might still be a nascent technology, but it's moving quickly into the mainstream. TV prices are dropping quickly; smartphones are starting to get 4K screens and 4K cameras, and now two semi-pro/consumer cameras are on the market: the $1,700 Panasonic Lumix GH4 and the $2,000 Sony FDR-AX100. (Yeah, neither name rolls off the tongue.) Both come at roughly the same price, but they offer very different experiences and capabilities, suitable for different types of buyers.
Let's look at how they compare.
Look and feel
For starters, they are different kinds of cameras. The Panasonic, as a micro-four-thirds mirrorless camera, is a 16MP still-camera that can shoot 4K video. The Sony AX100 is a 4K camcorder that can also take 20-MP still-images. As such, the Panasonic has the classic, tall DSLR-type shape that is best for photos, while the Sony has the long camcorder shape best for shooting video. Using either device for its secondary function will involve a bit of an ergonomic compromise. But shape in itself doesn't necessarily determine which is best for shooting 4K video.
In terms of lenses, the Sony AX100 has a fixed model that you can't swap out for another lens, but with a 12X zoom, from a wide 29mm to a very long telephoto of about 300mm (in 35mm equivalent), this lens probably covers all the range you'll need. It is also a pretty "fast" lens, with an aperture range starting from F2.8 at the wide end and from F4.5 at telephoto. These large apertures let in more light for low-light shooting and offer more flexibility in blurring out the background for shallow depth-of-field in a shot.
The lens situation is critical to understanding the real prices of the two cameras. The Sony AX100 sells with its 12X zoom lens for $1,999.99. The Panasonic GH4 is an interchangeable-lens camera, and it sells for $1,699.99, body only. Then you have to purchase a lens. To roughly match the zoom range of the Sony, you'd need the $1,800 Panasonic 14mm-150mm DSLR lens (28mm-300mm in 35mm equivalent), plus Panasonic's $170 DSLR to micro four-thirds camera adapter. Total price: $3,670. In exchange, however, the Panasonic offers far more flexibility. You may not need a 12X zoom — if so, you can chose shorter lenses that may have other bonuses, such as a larger range of aperture sizes. Or you could add a special-effect lens, such as a fish eye for an ultra-wide distorted look or a macro for an extreme close-up.
The naming of sensor types is horribly confusing and inconsistent. The largest is called full-frame; the most common on DSLRs is called APS-C. Others are measured in ratios such as 1/2.3. So some translation is in order.
On all its mirrorless cameras, Panasonic uses a sensor type called micro four-thirds, which measures 21.6 x 17.3 millimeters, for a total area of 225 square millimeters. Sony's AX100 camcorder uses what's called a 1" sensor, measuring 15.86 x 13.2 millimeters, for a total area of 116 square millimeters. So the Panasonic has a distinct advantage, with a sensor nearly twice as big. Larger sensors tend to do better in low light (high ISO settings). But that's only a rule of thumb, as it depends on the quality of the sensor and the capabilities of the imaging processor. Without seeing footage of both cameras, it's hard to know which will actually perform better.
MORE: What Is 4K TV?
In any case, both sensors are far smaller than those of professional video cameras or DSLRs that shoot professional-grade video. Full-frame DSLRs, for example, have sensors measuring around 860 square millimeters, though none of them shoots 4K video.
The two cameras are well matched in terms of video formats. Both support the version of 4K that TVs use — with a resolution of 3840 × 2160 pixels — also known as Ultra HD or UHD. Each camera shoots this resolution at both the 30 frames per second rate associated with a "video" look and the 24 fps style of movies. Each camera also shoots 1080p HD video at 60 fps, 30 fps and 24 fps.
The Panasonic GH4, however, also shoots the higher-resolution 4K that filmmakers use, with a resolution of 4096 x 2160 pixels at 24 fps.
The Sony AX100 is really a consumer video camera, albeit for consumers with high-end ambitions. It could well be used to shoot a "real" movie that could get into a film festival. But this camera lacks some features that the pros want. Chief among them is the ability to change lenses, which the Panasonic GH4 does offer.
The Panasonic has other pro attributes, too, such as its support for full 4K at the 4096 x 2160 resolution pro filmmakers use. It also supports more bitrates in all of its video formats to give more flexibility to filmmakers. In addition, Panasonic sells a $2,000 adapter that provides the kind of advanced inputs and outputs that professional videographers use, such as dual XLR audio input ports and monitors to keep track of the audio level of each channel.
However, both cameras lack the ability to put out raw, or very lightly compressed, video. And that is one of the main differences between them and true professional cameras that cost many times more. With built-in compression to formats such as MP4, both cameras toss out much of the visual information that higher-end cameras capture. Furthermore, these consumer cameras use smaller sensors to capture the data than those in true pro cameras.
Both the Panasonic GH4 and Sony AX100 bring 4K video creation to the masses — at least those masses willing to make a medium-sized investment. The GH4 has more flexibility, however. Since it is based on a popular micro-four-thirds still camera design, it should offer solid still-photography as well as 4K and HD video options. Fully equipping it for video shooting raises the price considerably, due to the required lenses and adapters. But it can ultimately deliver pro-like features.
The Sony AX100 is really a camcorder with photography as an add-on. For the best photo performance, it would be better to buy one of Sony's digital cameras, such as the upcoming Alpha a6000. But Sony's camera is nicely packaged for a "prosumer" video enthusiast, including a powerful zoom lens included for the moderate $2,000 price.