Pocket movie maker? We examine the Sony RX100 III's video mode

Movie Mode

There are two significant improvements related to video recording on the RX100 III: full sensor readout and support for the XAVC S codec.

On the previous RX100 models (and most other cameras on the market), the camera doesn't read all of the sensor's pixels when recording video, but instead skips lines to keep the amount of data being processed manageable. This results in vertical gaps between the horizontal lines used for the video, which decreases the sampling frequency, thereby increasing the risk of moiré. In contrast the Bionz X processor on the RX100 III is capable of reading all 20 million pixels sixty times per second, then downsizing these images into individual video frames. In effect it's oversampling the scene to optimize the quality, and reduce the risk of moiré.

Another boost to video quality comes from the addition of the XAVC S codec, which records 1080/60p video at a high bit rate of 50Mbps. Compare that to 28Mbps at 1080/60p and 24Mbps at 1080/24p on the previous model, and you can again see that there's a lot more data to work with, hence the promise of higher video quality. For those who want to record high speed video, the RX100 III also allows you to shoot at 720p at 120fps using the same 50Mbps bit rate.

The XAVC S system saves its files in MP4 wrappers alongside a variety of associated files, in a folder structure inside a folder called 'Private' on the memory card (though not the same structure as AVCHD files). These files are not recognized by all video playing software, but we found VLC would play them back and YouTube will accept them. Do note that an SDXC card is required for shooting XAVC S - the camera will throw up an error otherwise.

Sound is recorded using LPCM (linear pulse code modulation) rather than Dolby Digital (AC3), which is possibly due to the higher bit rate.

Video specifications

Apart from XAVC S, the rest of the video specs are the same as on previous RX100 models. Aside from Panasonic's Lumix DMC-GH4 and other high-end interchangeable lens cameras, nothing else comes close to the RX100 III at this point in time, at least in terms of specs.

Sizes	• XAVC S (Requires SDXC memory card) 1920 x 1080 60p Avg. 50Mbps 1920 x 1080 60p Avg. 50Mbps 1920 x 1080 24p Avg. 50Mbps 1280 x 720 120p Avg. 50Mbps • AVCHD 1920 x 1080 60p Avg. 28 Mbps (highest quality) 1920 x 1080 60i/50i Avg. 24 Mbps (high quality) 1920 x 1080 60i/50i Avg. 17 Mbps (standard quality) 1920 x 1080 24p/25p Avg. 24Mbps (high quality) 1920 x 1080 24p/25p Avg. 17Mbps (standard quality) • MP4: 1440 x 1080, 1080p (30/25fps), Avg. 12Mbps 640 x 480 (30/25fps), Avg. 3Mbps
Audio	• LPCM (2ch) / Dolby Digital (AC-3) / MPEG-4 AAC-LC • Stereo audio capture via built-in mic.
Format	XAVC S / AVCHD / MPEG4
Recordable time	Approx 29 mins for XAVC and AVCHD, 20 minutes for MPEG4 (1440 x 1080)

Features

The RX100 III provides videographers with an impressive set of tools. As you'd expect, you can adjust shutter speed and/or aperture. In manual ('M') mode, you can fix the aperture and shutter speed, and use Auto ISO to maintain brightness. The RX100 III also has an ND filter which can be turned on or off in movie mode (the 'Auto' option is for stills only).

Video Image Stabilisation

There are three image stabilization modes available for video. There's the regular optical SteadyShot, an 'Active' mode for increased shake reduction, and an 'Intelligent Active' feature for when things really get bad. The 'catch' with the active modes (which incorporate digital correction in addition to optical) is that a portion of the image is cropped in both directions. This lowers the resolution, and the lens's effective focal length is increased too.

Above you can see how much of our test scene is cropped by using the Active and Intelligent SteadyShot modes. Active SteadyShot uses a smaller proportion of the scene (86% to be exact) in order to compensate for more severe camera shake. This area is then enlarged to 1920 x 1080, which reduces the video resolution. There's also a change in effective focal length: the native 24-70mm equivalent, already increased to 25.5-74mm by the 16:9 crop, increases further.

The crops below illustrate the drop in resolution that comes with using Active and Intelligent Active SteadyShot. It's clearly noticeable in the text and Siemens star, and things get even worse when you use the Intelligent mode. However the digital corrections in the Active modes should bring their own benefits - most obviously they can compensate for roll movements of the camera around the lens axis, which optical stabilisation alone can't correct.

	Standard SteadyShot (i.e. optical only)
	Active SteadyShot uses 86% of the area to give around a 1.16x crop. The lens range is around 30-86mm equivalent at this setting.
	Intelligent Active SteadyShot uses 77% of the area to give a 1.29x crop. The lens range is around 33-96mm equivalent at this setting.

If you're recording at 120 fps - which is captured at 1280 x 720 rather than 1920 x 1080 - an even smaller slice of the total scene is used. As illustrated below, there's also a large drop in resolution.

	When you shoot at 120 fps there's a significant drop in resolution when compared to the SteadyShot standard example above. The resolution appears a long way below the 720p output res. The lens range is around 43-126mm equivalent at this setting.

Manual focus and exposure warning displays

When focusing manually, Sony provides a 'peaking' display (in your choice of colors and intensities) to allow pull focusing from one subject to another while recording. If would've been nice had Sony put a touchscreen on the RX100 III, which would allow you to obtain a similar effect with autofocus. You can also enlarge the frame while recording - just as with stills - with or without peaking enabled.

Another useful tool for shooting video is zebra pattern, which highlights potentially overexposed areas of the scene. The threshold at which the pattern appears can be set from 70 to 100+. You can see how it looks from the screenshots below.

New to the RX100 III is 'zebra', an exposure warning display. The threshold at which stripes are displayed can be set in 5% increments from 70 to 100, with an additional 100+ options only showing totally overexposed regions. Zebra stripes continue to be visible while you're shooting movies (without affecting the recorded footage).	Zebra can be combined with focus peaking, if you're manually focusing your video. Buttons can be assigned to engage and disengage both features quickly, so you don't have to have them both visible throughout shooting.

Audio choices are pretty basic. You can adjust the mic level between low and normal, or turn on a wind filter. There's also a Auto Slow Shutter setting (which is on by default), which lowers the shutter speed automatically in low light, to reduce image noise, at the cost of more blurred frames.

Another nicety is that the RX100 III can output uncompressed 4:2:2 video over HDMI. This allows you to send video directly to an external recorder - something serious videographers will appreciate. With the camera's 'HDMI Info. Display' option set to 'Off' the camera continues to show all the shooting details on the back of the camera, while outputting the uncompressed 8-bit video feed over the HDMI lead. When set to 'On' the camera's rear screen blacks out and the HDMI signal duplicates what would otherwise be on the LCD - ideal for if you're using an external monitor.

Handling

Once you've got used to the movie recording button - which is set way too deep within the back plate - recording video can be as simple or as complex as you want it to be. Something video enthusiasts may want to do is change the SteadyShot mode from Active to Standard, to get higher resolution footage.

Video can be recorded in any shooting mode, or you can select to only use the dedicated movie mode position on the mode dial. Its main advantage is that it previews the correct framing, including any crop introduced by Active SteadyShot. In the regular shooting modes, the camera has to switch aspect ratios and crop in when you hit the record button.

Regardless of what mode you're in, exposure, focus mode, ISO, and the ND filter can all be adjusted while you're recording. Focus peaking and zebra can also be turned on and off. Exposure is adjusted using one or both of the control dials, which you can configure to your liking. Other settings can be changed via the Function menu, though that can distract from your workflow. Functions you want to quickly turn on and off, such as zebra, can be assigned to one of the custom buttons.

The manual focus tools work well. Focus peaking is effective, and as with any camera, you'll need to work out how the displayed peaking level relates to actual subject distance. Something that would make manual focus easier is a distance guide, which isn't available for stills, either.

One last thing worth pointing out is that there is a roughly one second delay between the time you press the red button and when recording actually begins.

Video Quality

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Its full sensor readout and high bit rate allows the RX100 III to produce noticeably higher resolution video compared not only to its predecessors, but nearly all of the other cameras in the above widget. In the initial scene above, you can easily see how much crisper everything looks compared to the RX100 II. The amount of moiré is quite a bit lower, as well. One other camera that uses full sensor readout is the Sony Cyber-shot DSC-RX10, and the results are nearly identical to that of the RX100 III. (The RX10 doesn't offer the XAVC S codec, though.)

Other enthusiast compacts can't keep up with the RX100 III - even the Canon PowerShot G1 X II, despite its larger sensor. And, if you think that a full frame camera will perform better, we have bad news for you. The bottom line here is that full sensor readout is a real game-changer in the world of digital video.