Photos taken by prototype Lytro cameras, when viewed through most current Web browsers, allow users to click on different parts of an image to bring different subjects into focus.

Lytro lists other benefits. For one thing, since images are focused after the fact, users don’t have to spend time focusing before shooting. Nor do they have to worry if they wound up focusing on the wrong thing.

The technology works in very low light without a flash, Lytro said, while 3-D glasses can add a particularly vivid effect—simulated three-dimensional images that users can adjust to show different perspectives.

Conventional digital cameras essentially record the total sum of light rays from a scene as they hit an image sensor, Mr. Ng said. A light-field camera records the color, intensity and direction of rays individually. He compared the approach to audio recording; instead of recording multiple musicians all at once, modern multitrack studios record them separately so that the volume and other effects can be independently adjusted after the fact to create a sound mix.

A key to Lytro’s strategy is to use the increasing resolution found in the image sensors in conventional digital cameras, capability that Mr. Ng said most amateur photographers don’t fully exploit.