A few months after teasing the new cameras at PMA 2010 (with almost no details), Sony officially announced the interchangeable-lens Alpha NEX-3 and NEX-5 today. Both cameras will be available in July.

The NEX camera bodies are impressively thin and light, measuring about an inch thick and looking noticeably more slick and slim than competing interchangeable-lens cameras from Panasonic, Olympus, and Samsung. These are the first interchangeable-lens cameras we've seen that honestly approach the size of a point-and-shoot camera.

The Sony Alpha NEX-5 and NEX-3 both offer 14.2-megapixel APS-C CMOS sensors; it's the same size sensor found in Samsung's NX10 interchangeable-lens camera and in several full-size DSLRs, but it's significantly bigger than the Micro Four-Thirds sensor in cameras from Olympus and Panasonic.

On the video side of the equation, the Alpha NEX-5 will shoot 1080i high-definition video in either AVCHD or MPEG-4 format, while the slightly lower-end NEX-3 maxes out at 720p MPEG-4 video. The other key difference between the two NEX cameras involves the body build: The NEX-5's body is made out of magnesium alloy and has a larger grip, while the NEX-3 has a polycarbonite body available in different color options (silver, black, and red).

The NEX cameras handle SD, SDHC, and SDXC card formats, as well as Memory Stick cards; the one storage slot on the cameras takes both card formats.

The announcement means that there's yet another lens mount to think about, as well. The Sony Alpha NEX series will use the brand-new E-Mount lens system, and the two new cameras offer no body-based image stabilization.

Lenses using Sony's Optical SteadyShot stabilization system--a stabilized 18mm-35mm f3.5/f5.6 zoom lens, as well as a 16mm f2.8 pancake lens--will be available, including in the Alpha NEX's kit configurations. The NEX cameras have a focal length multiplier of 1.5X, meaning that the 18mm-55mm zoom lens has a 27mm-82.5mm field of view in 35mm film equivalent, while the prime lens is a 24mm-equivalent wide-angle lens.

A third, optically stabilized, 18mm-200mm f3.5/f5.6 zoom lens will be available separately in the fall for $800 (not in any kit configuration), which Sony says is optimized for shooting video. In addition to the E-Mount lenses, an adapter that lets you use Sony's A-Mount lenses with the camera will be sold separately for $200.

The Sony Alpha NEX-3 will sell as a kit with the 16mm prime lens for $550, or with the 18mm-55mm zoom lens for $600. The Sony Alpha NEX-5 will cost $650 with the 16mm prime lens and $700 with the 18mm-55mm zoom lens.