Startup Lytro on Wednesday unveiled a camera that lets people adjust the focus on photos after they take them.

Work that Ren Ng started in a lab while working on a PhD at Stanford University about eight years ago has led to the creation of what is billed as the first camera that captures the entire light field in a scene.

"Our goal is to forever change the way people take and experience pictures, and today marks our first major step," Ng said as pocket-sized, telescope-shaped Lytro cameras made their public debut in San Francisco.

"Light field photography was once only possible with 100 cameras tethered to a supercomputer in a lab," he continued.

"Today it's accessible to everyone in a camera that's small and powerful, but incredibly easy to use."

The Silicon Valley company began taking limited orders in the United States for two Lytro camera models, a $399 version capable of holding about 350 pictures and one priced at $499 offering twice the memory space.

Lytro cameras with eight gigabytes of storage were being offered in blue or graphite, while the higher priced model was red.

People could place orders online at Lytro.com, but cameras won't be shipped until early next year.

Software tailored for Macintosh computers will use light data captured by the cameras to allow points of focus to be easily shifted in digital images in a feature that Lytro called "Shoot now, focus later."

Lytro promised that a version for computers powered by Microsoft's prevalent Windows operating systems will be available later.

Lytro has tested prototypes of the camera with photographers.

Ng referred to Lytro camera images as "living pictures" because they allow whoever is looking at them, say as a post on a Facebook page at Twitter, to shift the focus between people or objects captured in photos.

When the Lytro pictures are shared online, the "light field engine" travels with each image so anyone can interact with them on web browsers, smartphones, tablets or other devices, according to the startup.

Ng said in a blog post that Lytro's is intent on making conventional cameras a thing of the past.

Most of the reported $50 million in funding for the startup has come from Andreessen Horowitz.

Lytro said it aims to shake up a global digital still-camera market expected to grow from $38.3 billion last year to $43.5 billion by 2015.