Photosynth: Microsoft Takes on Photo-sharing 3D

Even if you've never been to the Notre Dame cathedral, chances are you've seen plenty of pictures. But looking at a snapshot or two, or even a dozen, doesn't come close to giving you the feeling that you've actually been there, that you've walked around the place. Photosynth—a free photo-sharing service launched Thursday by Microsoft Live Labs—may just change the way you look at Notre Dame or the rest of the world.

Photosynth is an ingenious new technology that gathers multiple photographs of one thing (a room, a house, a piece of furniture, a landscape), taken from multiple angles, and stitches them together into a three-dimensional panoramic quilt. By combining anywhere from a dozen to a couple hundred pictures of, say, Notre Dame, Photosynth lets you click your way through the cathedral's physical space. Circumnavigate the Gothic masterpiece, take it all in from a hundred yards away, then zoom right up the nostrils of Adam and Eve, lounging by the western rose window. Enter the building to admire its organs; look up at its vaulted ceilings—all from your PC. "This is really a new medium," says Blaise Aguera y Arcas, one of the lead engineers on the project. It's hard to argue with him.

The software is relatively straightforward. It's free, and new users automatically get 20 gigabytes of memory to play with. Once you download it from the Photosynth site, you can browse "synths" that other users have already uploaded (be sure to check out the jaw-dropping tour of the National Archives; walk right up and examine the penmanship of the Constitution.) To make your own synth, upload a series of photos of, for example, your office. The more pictures, the better—just make sure there's a lot of overlap between photographs to make it "synthy." Each photo is analyzed by an algorithm that identifies specific features: the plane of your desk, the curve of a chair, the spines on a bookshelf. Photos that share features are synced together. The more times a given feature from your office appears in photos, the more accurate its spatial placement will appear in relation to other objects.

Once you have uploaded your batch, hit the "synth" button and sit back while the magic happens. One caveat: you may be sitting awhile. My first attempt took about 15 minutes, largely due to my computer's relatively low memory and sluggish bandwidth. There's also a bit of a learning curve and there are no privacy settings yet, so everyone can see your botched experiments. I made a failed synth of my own office (Michael Bucher, our able young photo intern, and I neglected to take enough overlapping snapshots). In order to get better at the process, you have to relearn how you think about taking pictures. No nook should go untook.

Photosynth incorporates a technology that Aguera y Arcas designed—and discussed in a widely circulated lecture last year—called Seadragon, which can zoom and pan with incredible smoothness over millions of pixels. Using that as a backbone, Photsynth similarly allows for continuous navigation: the software selects and almost-seamlessly displays photos as the user moves through online space (the 3D effect is marred by occasionally pixilated fuzziness of peripheral photos). If you take pictures a full 360 degrees around a stationary object, Photosynth lets you spin it around on its axis using an inner-tube-shaped navigation button. You can even adjust for color and lighting to further streamline the immersive effect. That is, provided you're on a PC. As of now, Photosynth runs only on Windows XP and Windows Vista. "This would be a good client for the Mac," concedes Aguera y Arcas, who says that option remains open down the line. Also for the time being, you can only see synths on the actual Photosynth site—you can't embed them on your own blog or even e-mail them to friends.

For now, the software's coolest feature is its ability to incorporate photos taken by different people at different times and on different cameras. The technology is sophisticated enough to see through the differences among the images and spot similarities (ah, if only people were more like Photosynth). So if you asked all your friends to send you pictures they've taken of Notre Dame, you could conceivably build a pretty decent synth out of them. What you can't do yet, and what Aguera y Arcas says will someday be possible, is collaborate on other existing synths, pull other people's public photos into your own streams, or open your synth to other contributors. That's clearly where the real potential is: If Photosynth users were allowed, for example, to take any photo tagged "Notre Dame" from Flickr (under a Creative Commons license, natch), you could potentially "crowd-source" an amazingly comprehensive Notre Dame synth.

The technology behind Photosynth holds out great promise in the long run. It's fun to imagine new story-telling techniques or artforms that may evolve along with it. Certainly real-estate agents and art galleries (and enterprising smut peddlers) are going to have a field day with it. Eventually, you could perhaps even comb through every photo online and build a 3D model of the entire planet. That would be undeniably cool. Still, despite all of Photosynth's virtual potential, nothing beats actually visiting Notre Dame in person.