Although it uses the same 20.1Mp 1-inch type back-illuminated Exmor R CMOS image sensor as the RX100 II, the RX 100 III features the new Bionz X processing engine which brings Sony's diffraction reducing technology and area-specific noise reduction for improved image quality.
The big news, however, is that Sony has managed to squeeze in a pop-up electronic viewfinder while making the camera only about 2.5mm wider and 9 grams heavier than the RX100 II. This is a 0.39-inch OLED unit comprised of 1.44K dots with Zeiss T* coating for better clarity.
Sony has also improved the tilting bracket that holds the 3-inch 1,228,800-dot LCD so that the screen can be tilted up through 180 degrees, making it useful for shooting selfies.
Sony has changed the lens for the RX100 III. The RX100 II lens has a focal length range equivalent to 28-100mm, but the RX100 III has a Zeiss Vario-Sonnar T* 24-70mm (equivalent) f/1.8-2.8. This makes it more useful for shooting indoors, street photography and shooting landscapes.
The maximum aperture has also changed to f/2.8; it's f/.49 on the RX100 II.
Like the RX100 II, the Mark III has a ring around the lens that can be used for controlling a customisable parameter such as aperture, and the there's a Function menu that displays 12 user-selectable features. There's also a new Custom button which can give quick access to one of 43 features.
Wi-Fi connectivity is included along with an NFC chip for speedy connections via NFC enabled smartphones and tablets. However, for the first time in an RX100 camera there's Sony PlayMemories support which means that users can download apps to extend the functionality of the camera.
The RX100 III can record Full HD movies and, in addition to the common AVCHD format, footage can be recorded in XAVC S format - a variant of the XAVC format used by many professionals. Dual video recording simultaneously stores small MP4 format files for easy sharing along with high-quality AVCHD / XAVC S files.
To help with exposure, 'Zebra' patterning can be displayed on the LCD and in the viewfinder to highlight the brightest areas in a scene. There's also Focus Peaking to indicate the sharpest areas when focusing manually.
Although 4K video recording isn't possible, the camera outputs 4K stills to 4K televisions via an HDMI mini cable.
The price and on-sale date of the RX100 III has yet to be announced, but the market signs point to a retail release around mid-June.