Capping months of rumors and speculation, Samsung has announced its Galaxy S III smartphone at an event in London today. Major specs include a 4.8-inch PenTile Super AMOLED display at 720p resolution, 8-megapixel primary and 1.9-megapixel front-facing cameras with 990ms start-up time, 3.3fps burst mode, and best-shot selection (similar to the HTC One series), 16 or 32GB of storage (a 64GB version is coming later) with microSD expansion, Bluetooth 4.0 support, GPS with GLONASS reception, high-throughput 40MHz 802.11n Wi-Fi, NFC, and a relatively large 2,100mAh battery. The global version of the device will be using the recently-announced Exynos 4 Quad quad-core system-on-chip — regional variants could be using alternatives, just as the Galaxy S II did. The phone measures 8.6mm thick (136.6 x 70.6 x 8.6mm, to be exact) which is actually a bit thicker than the S II's 8.5mm. The global version will support 21Mbps HSPA+, though Samsung is quick to point out that certain local models will have 4G.

The hardware seems incremental over the Galaxy Nexus released late last year, but Samsung's touting some fascinating software customizations — an emphasis on "natural interaction," it says — that'll debut in the S III. First off, Smart Stay uses the front-facing camera to monitor your eyes and maintain a "bright display for continued viewing pleasure." S Voice is a Siri-like customized voice recognition system that allows the phone to recognize a variety of commands at any time — as an example, Samsung says you can simply say "snooze" to shut off your alarm when it goes off. S Beam, meanwhile, is an enhanced version of the Android Beam system that launched in Android 4.0 and allows large files to be transferred between phones quickly — a 1GB file within 3 minutes, for instance. Something called "Pop up play" lets the user watch a video anywhere on the screen while continuing to use other apps, good for watching a video attachment without leaving your email.

Samsung is also enhancing its DLNA-based AllShare media sharing system with a few additional modes. AllShare Cast allows content on the phone to be immediately sent to a compatible display; AllShare Play lets you send media "regardless of the distance between devices," suggesting that it may route content through the internet to reach its destination. The most intriguing mode may be what Samsung is calling "Group Cast," which shares your phone's screen with other users on the same network and allows them to annotate and add comments — good for an ad-hoc presentation with coworkers, for instance.

There's no word on carriers or pricing, but Samsung says that Europeans can look for the Galaxy S III to launch on May 29th with the 32GB model as a Vodafone exclusive for the first month; other markets around the world will follow after that. Specifically, the company says that 4G versions will be coming to North America and Japan in summer — and the US will see it in June.

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