Performance

Like its predecessors, we found the Cyber-shot DSC-RX100 to be a capable performer, with good focus and shot-to-shot times and impressive continuous shooting speeds. The startup time is significantly improved over the M2 - taking around 1.6sec from power-on to first shot, rather than the II's 2.2sec.

The middling battery life - particularly when making extended use of the electronic viewfinder - was a minor annoyance, not helped by the need to charge the battery in the camera or shell-out for an external charger. Byond this, the only real disappointment was how the camera 'locks up' for over ten seconds when shooting a long series of JPEGs (it's not quite as bad with Raw, as the bursts are shorter).

Operational Speed

It takes about 1.5 seconds for the Cyber-shot DSC-RX100 III to extend its lens and prepare for shooting. The camera can be powered on the 'old-fashioned way' or by popping up the EVF. Something that some folks may not like is that the RX100 III powers off when you put the viewfinder back down. It would be nice to have a choice in the matter.

The camera is very responsive when taking a photo, with no discernable delay between half and fully pressing the shutter release. You can fire off the next picture in just a third of a second.

AF System & Performance

The RX100 III's autofocus performance is very good in most lighting conditions. There are minimal delays, and the camera did a fine job of focus on the desired subject. Low light performance is noticeably slower, with focus times hovering just under a second. As we've seen on other recent Sony cameras, the camera is more likely to select an actual focus point with the AF illuminator turned off. Otherwise, it'll just give you a big green box,

Continuous Shooting

There are two different continuous shooting modes on the DSC-RX100 III: regular continuous and speed priority. Sony claims speeds of 2.9 fps for regular mode and 10 fps in speed priority mode, which locks exposure and focus at the first shot.

Do note that you cannot use the Xtra Fine setting when shooting Raw+JPEG. These tests were conducted using a SanDisk Extreme Pro UHS-II card, rated to the U3 continuous read/write standard and capable of up to 280MB/s read speeds.

Timing
Large/X-Fine JPEG
Raw
Raw+Fine JPEG
Frame rate 3.3fps 2.7fps 2.7fps
Number of frames ~71 ~53 35
Buffer full rate 1.4fps 1.7fps 1.2fps
Write complete 28sec 13sec 18sec

In 'Speed Priority' mode, things are even more rapid, though come at the cost of...

Timing
Large/X-Fine JPEG
Raw
Raw+Fine JPEG
Frame rate 10fps 5.9fps 6.5fps
Number of frames 47 26 23
Buffer full rate ~2fps 1.7fps 1.2fps
Write complete 21sec 13sec 18sec

These are impressive numbers for any compact camera but there are two factors that stop us being too impressed. Firstly, the camera is almost entirely unresponsive while it's writing to the card; it'll snap another shot if you want one, but pressing the playback or menu buttons will yield an error message or no response at all. Secondly, the autofocus performance doesn't really live up to the continuous shooting performance.

Autofocus

The RX100 III is a little faster than its immediate predecessor, when focusing in good light, but this advantage is questionable in lower light with low contrast subjects, where the camera can hunt. This becomes more of a problem if you're stopping the camera down: the M3 is much more likely to use the specified aperture to focus, rather than opening the aperture up during autofocus - slowing the M3 still further.

Here's an example of a shot the RX100 III found hard to find focus for. The light level is reasonable (6EV), but it took several attempts to get the camera to focus on the subject, even using center focus point.
Photo: Barney Britton

Continuous focus isn't a particular strong suit on the RX100 III, but it is capable. Although the frame rate drops to ~3 fps with continuous AF, the camera is able to refocus on moving subjects, albeit sometimes with a bit of a lag. The RX100 III can even follow face around the frame and continuously focus on it during bursts. In 'Wide' AF area mode, the camera tries to intelligently focus continuously on whatever it is in the frame it thinks is your subject (some competitors only focus centrally during bursts). That said, the camera's generic subject tracking 'Lock-on AF' is highly unreliable, and can lose its subject quite easily.

One frustration we had with the RX100 III was that its Face Detection mode isn't as effective as we'd like it to be. It sometimes struggles to find faces in the scene (particularly ones wearing glasses) and can 'lose' faces just as you're about to take the shot, reverting to any already-specified focus point.

Battery Life

The Cyber-shot DSC-RX100 III uses the same NP-BX1 lithium-ion battery as its predecessors. This battery contains 4.5 Wh of energy, which translates to 320 shots per charge using the CIPA standard - the lowest of the three RX100 models. Use the viewfinder and the number drops to a much less useful 230 shots per charge. As always, using Wi-Fi will decrease that number considerably.

The battery inside the RX100 is charged internally via a USB cable (attached to a wall socket or your computer). This certainly adds convenience, making it easy to find somewhere to keep the battery topped-up, but the lack of external charger means it's difficult to keep a second battery fully chanrged. It takes 230 minutes to charge the battery in the camera.

This extra time and , it makes a lot of sense to pick up one of the BC-TRX external charger, which is considerably faster than using USB.