It says a lot that Sony felt confident enough to keep an nearly 3 year old camera around in its lineup, but the RX100 really is that good. It won our award for the best compact camera of 2012 and it's still probably the best compact camera available for $500. If you're looking at the Sony RX100 for $500 (or less!) and fretting that you can't afford the latest and greatest, fear not. Sony outdid themselves with the RX100 and it's a no-brainer if you've only got $500.
Skipping two generations like this means we're comparing two pretty different cameras. The size and weight of each generation inched up a bit, and while the difference was negligible between each generation, it's more pronounced when comparing the Mark III with its grandfather. The original RX100 is a noticeably more compact camera than the Mark III: 17% lighter and 12% thinner.
Since the RX100 III returns to the original formula in dropping the hot-shoe found on the Mark II, that drawback relative to the Mark II is moot. Enthusiast photographers will sorely miss the superb electronic viewfinder on the Mark III and will be disappointed to lose the built-in 3-stop neutral density filter, among other features. Casual shooters will miss the 180 degree tiltable screen and Wi-Fi (lackluster though it may be).
The big difference between these cameras is in low-light situations. While the original RX100 is no slouch in this department, the RX100 III is the clear champion. There are two big advances that enable the Mark III to shine here. The first is the backside-illuminated sensor Sony introduced in the RX100 II and retained on the RX100 III. This is good for a 1-stop improvement when comparing JPEGS from the RX100 to the RX100 II: ISO 1600 on the Mark II looks as good as ISO 800 on the Mark I. The second factor is the faster lens at 70mm on the Mark III, which means you can shoot at ISO 800 and f/2.8 on the Mark III when you'd need to jump to ISO 1600 and f/4.0 on the Mark I. Put together, the RX100 III is 2 whole stops faster than the RX100 at 70mm.
It's easy to give the nod to the RX100 III. Its only actual downside in terms of features is the loss of 30mm of zoom, which is compensated somewhat by a 4mm wider wide angle. But that leaves out the RX100 III's $300 premium, meaning this isn't really a fair fight. If anything, it's interesting to see what 3 years of development have yielded. Perhaps more interesting is the fact that a 3-year-old camera still arguably holds the title of best compact camera under $500. That in itself says a lot about the maturity of the digital camera market and Sony's ascendancy.
Maximum effective ISO is an estimate of the highest sensitivity at which a camera can capture excellent quality photos.
Cameras with higher effective ISO will be better choices for indoor photography, night shooting, and indoor sports photography, especially if you intend to make large prints.
You can learn more at our glossary entry.
Maximum effective ISO test data courtesy of DxO Mark.RX100 III test data on DxO Mark RX100 test data on DxO Mark
Excellent high-ISO performance for such a compact model; Smart controls; Small body; Bright lens; 10fps full-res burst mode; Very fast shutter response; Excellent LCD.
Lens flare at night; Poor rendering of yellows; Slow flash recycling; Soft corners wide open; Continuous AF mode slow to lock.
Pocket-friendly design; Popup electronic viewfinder; Bright lens across the zoom range; Great performance with very fast autofocus; Very high resolution gives lots of detail in good light; High ISO noise levels much better than most pocket camera rivals; Wi-Fi wireless networking
Feels a little unbalanced without an accessory grip; Not as much telephoto reach as its siblings; Noise processing is heavier-handed than in earlier models; Quite pricey for a fixed-lens camera