Sony's RX line of compact cameras are undeniably amazing. On the high-end, there's the RX1, a $2800 camera with a full-frame sensor that also fits in your pocket. It has been very well received and reviewed by camera enthusiasts, and I loved every minute I was able to use it at CES. Professional photographers have adopted it as a great secondary camera to complement their full-frame DSLRs, if they have the budget to do so. On the (relatively) low-end is the $650 RX100, which I tested late last year. I found it to be the ideal companion camera for my DSLR; its size allows it to go places a DSLR (or mirrorless camera) can't, without sacrificing too much image quality. A 1-inch image sensor can go much farther than the 1/1.7-inch sensor you find in Canon compact cams like the S100.
Today, Sony announced follow ups to both the RX1 and RX100, dubbed the RX1r and the RX100 Mark II. These cameras don't replace the two original RX models, but change and add features with specific areas of focus. The RX1r is an offshoot of the RX1, using the same 24.3MP full-frame sensor paired with a fixed 35mm f/2 Zeiss lens. The difference is that the RX1r removes the optical low-pass filter in the RX1 to achieve finder detail resolution in its images, which is useful for landscape photographers. The pixel resolution hasn't changed--it's the amount of detail that's resolved that's theoretically improved. The tradeoff is that the RX1r is more vulnerable to moire and false color artifacts, which early tests have confirmed. It ships in July for the same $2800 price as the RX1.
Much more interesting is the RX100 Mark II, which costs $100 more than the RX100. Sony's made some considerable changes here, none of which I would consider a compromise. First, the RX100 MkII has a new image sensor designed for low light sensitivity. It's actually a 1-inch back illuminated CMOS sensor, using a "reverse structure" approach like the backlit sensors found in smartphone cameras. Backside illumination puts the circuitry layer of the sensor behind the CMOS diode so more light can hit it. This is a costly process that's more suitable for tiny smartphone sensors than DSLRs, since the APS-C and full-frame sensors mitigate low-light noise by sheer size. Sony believes the 1-inch sensor is perfectly suited for this technology, and claims 40% better low light performance than the RX100.
Additionally, Sony has added a tiltable LCD to the RX100 Mk II (84 degrees upward, 45 degrees downward), 24p movie recording at 1080p, step zoom with the control ring, Wi-Fi and NFC, and its proprietary multi-interface hot shoe for camera accessories. The swivel LCD alone makes me feel all tingly inside--it's that useful. I should still mention that the f/1.8 zoom lens on the RX100 Mk II hasn't changed from the RX100. Aperture is wide at 28mm, but rapidly closes up to f/2.8 at 34mm and f/4.9 at full 100mm zoom. I also hope that lens distortion is better corrected in the RX100 Mk II than it was in the original. I can't wait to test this camera.
The RX100 Mk II also goes on sale in July. If the new sensor is as good as Sony says it is, this is the compact camera I would buy to complement my DSLR. I would still recommend an interchangeable mirrorless camera with an Micro 4/3 or APS-C sensor if you're just getting started, since you're going to get more bang for your buck with the larger sensor and lens options for learning photography.