Looking at these two cameras on paper, the Sony RX100 III seems like the easy favorite. Yeah you trade $100, 30mm of zoom and a hot-shoe, but you gain a beautiful, high-resolution pop-up viewfinder and a much brighter lens at telephoto. It's not the no-compromises, better-in-every-way difference between the RX100 and RX100 II, but it's a big step up.
We were blown away when Sony told us that they were able to drop the maximum aperture at 70mm from f/4.0 in the Mark I/II to f/2.8 in the Mark III while keeping the size of the lens constant. Even accounting for shaving off 30mm of zoom, this is a tough feat, and one that will give you the flexibility to better isolate your subject and shoot in lower light (f/2.8 will let you collect 2x as much light as at f/4.0). While we expected big tradeoffs in distortion or vignetting, we were happy to see Sony largely managed to maintain the optical quality of the RX line.
Sony also wowed us when they announced that the RX100 III would get the same BIONZ X processor found in Sony's flagship mirrorless cameras, the A7 and A7R. This chip gives the RX100 III the processing power to offer cool features like a 120fps slow-motion video mode. Neither the Mark II nor the Mark III are speedy to turn on, but Sony boosted the RX100 III's buffer significantly and Sony's 10fps claims were supported in our testing: the Mark III is just a speedier camera overall. We also expected the beefier processor to improve noise levels while retaining detail in the out-of-camera JPEGs.
Unfortunately, despite the $100 premium over the RX100 II, a refreshed sensor and the BIONZ X processor, we found no particular improvement in image quality. Instead, Sony appears to be applying more sharpening across the ISO range than it did on the Mark II, and manages to do so without the "halos" around high-contrast edges that sharpening usually creates. Overall there's sharper detail but not without drawbacks.
It turns out that the RX100 III exhibits noticeably more noise at higher ISOs. Smooth areas that the RX100 II handled with aplomb become splotched and noisy, starting at ISO 1600, and deteriorating significantly at ISO 3200. This was a bit of a disappointment and tempered our RX100 III enthusiasm a bit. Call us spoiled, but we've come to expect big jumps in image quality from each new generation of Sony cameras.
Note, though, that the different noise/detail tradeoff Sony made with the RX100 III probably won't be an issue if you're a RAW shooter. We obviously can't say for certain until RAW support is added to various programs for the RX100 III (for us, Adobe Camera Raw), but that's a fairly safe prediction. And of course, the f/2.8 lens at telephoto means you should be able to shoot at ISO 1600 with the RX100 III when you'd need to push ISO to 3200 on the RX100 II to compensate for the slower f/4.0 aperture at that focal length.
The single best feature of the camera was, for us, the built-in EVF. Not only is the RX100 III the smallest compact camera to offer a 1" sensor, but it's also one of the only compact cameras of its size to offer a built-in EVF. The image is bright and the resolution (at 1.44 million dots) is surprisingly high for such a small unit. Some photographers may lament the loss of a hot shoe, but we think the pop-up electronic viewfinder was a stroke of genius from Sony and well worth this compromise.
Sony impressed us with the RX10's video prowess and we were happy to see the best of that camera filter down to the Mark III. One welcome addition to the Mark IIII that hasn't gotten much attention is the built-in neutral density filter. Among other things, this can help you keep a large aperture when shooting video in direct sun, giving you a more cinematic subject isolation. Sony also added a fantastic stabilized video mode, giving your videos a professional, stabilized look, without having to crop in and reduce resolution in post. This is a big deal.
For us, though, the major coup was Sony's addition of the XAVC S 50Mbps codec, which allows for incredibly clear, high quality video recording. Unfortunately, all these video features come with one giant drawback: that missing accessory hot-shoe means you can't easily slap on an external mic. Even so, if you see yourself doing even a little bit of video work and you're up in the air, the Mark III is the clear favorite.
Sony has also increased the customizability of the camera, letting you set up to 12 custom shooting controls reached from the Fn button, versus 7 on the RX100 II. And the tilting LCD can flip up a full 180 degrees, letting you shoot selfies with your friends; maybe not a big deal for enthusiast photographers, but a great feature for cellphone users looking for a (major) jump in image quality.
At the same time, Sony reworked the menu system in ways that weren't always an improvement: rotating the menu wheel doesn't advance the menu when you get to the last item, but instead skips to the top of the menu you're on. The type is larger, but more settings are buried within sub-menus. A quibble for sure, but it's worth mentioning.
What it comes down to is this: while the RX100 III is a fantastic camera, it isn't the obviously superior choice for all photographers the way the RX100 II was clearly superior to the RX100. Casual shooters acquainted with cell phones may not care about an electronic viewfinder, and the loss of the 100mm telephoto reach of the Mark II will be a deal breaker for some. JPEG shooters may think twice given the regression in noise levels at higher ISOs. And if you just want great image quality in an affordable compact camera, the RX100 II gives you similar image quality at a lower price.
All these caveats aside, f/2.8 at 70mm on a compact camera with a generous 1" sensor is mighty impressive. While you lose 30mm on the telephoto end vs the RX100 II, the RX100 III's wide angle is 4mm wider; welcome news for landscape and street shooters. Add in RX100-series firsts like the built-in ND filter, EVF, and superior video bitrates, and it's not hard to argue that the Mark III is the best compact camera available for $800 or less.
New, 20.2MP, 1-inch type, backside illuminated (BSI) image sensor produces superb image quality, with particular improvements in low light and high ISO; 3-inch tilting rear LCD screen handy for composing shots from difficult angles; Fast all-around performer with quick autofocus and virtually no shutter lag; New, multi-interface hotshoe for adding a strobe or optional electronic viewfinder; Built-in Wi-Fi with NFC.
Bigger and heavier than previous model; More expensive than previous model; Reduced burst performance when shooting RAW files; Somewhat confusing menu structure and control layout; Wi-Fi features can be difficult to set up.
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