In a traditional setup, a camera needs two lenses spaced about as far apart as a pair of eyeballs to take a 3D image. The photo taken through each lens represents a visual "channel"--one right channel, one left channel--that sync up with your eyeballs to create the 3D illusion you see in the resulting image. After taking the two photos, the camera combines the two "channel" images into one image in various ways, depending on the playback technology. Slightly offsetting the two images or firing the left- and right-channel images in rapid succession gives the image or video simulated depth when viewed with special eyewear or on a specially coated display.
Few single-lens 3D cameras and convertible 3D lens options are available now, though they are still probably the best option for casual shooters today. Not everyone wants to invest in a twin-lens camera built primarily for 3D shooting; one-lens cameras are everyday models built for traditional 2D shooting, but they also let you experiment with 3D photography. Be aware, however, that single-lens cameras can take only 3D still images, not 3D video footage; you'll need a dual-lens device to make 3D movies.
Inside single-lens models, accelerometers and algorithms perform most of the magic. The cameras detect where each lens in a two-lens setup should be; then on-screen guides instruct the shooter to move the camera accordingly to frame a 3D shot. The camera performs the post-shot stitching and processing automatically, and the result is a single .MPO-format 3D image.
Single-lens 3D cameras: The major players in one-lens, casual 3D shooting are Olympus, Panasonic and Sony. All those companies now offer several single-lens point-and-shoot cameras that capture.MPO images in 3D. In general, the 3D effects aren't as stunning as you'll see with a traditional twin-lens setup, but the cameras provide convenient entry points into 3D.
Announced at CES, the Olympus SP-610UZ megazoom camera and the Olympus TG-610 and TG-310 rugged cameras have on-screen guides that help you create a simulated dual-lens image by following in-camera controls. You snap a first shot, and the camera guides you via accelerometer-driven on-screen controls to frame the second shot of the 3D image. The wide-angle 22X optical zoom lens of the SP-610UZ and the underwater-shooting capabilities of the TG-610 and TG-310 should offer some very creative uses for the cameras' 3D modes: topography-friendly mountain vistas and Jaws 3D-style oncoming fish, for example.