Photosynth uses lots of photos to put you amid a 3D scene

— -- First there was the snapshot, and then came video. Now comes Microsoft Photosynth, kind of something in between.

That's how Microsoft is marketing this brand-new visual medium, which launches Thursday. It's way premature to think Photosynth might someday have the long-lasting impact of still photography and movies. But the promising, if not quite polished, online service is fun and worth keeping an eye on — even with a few important drawbacks.

Photosynth is better seen than described. It aims to take panoramic stitching to a whole new level. The basic idea: automatically stitch together a collection of digital photos you took touring, say, Times Square or Tiananmen Square and transform them into a three-dimensional, 360-degree online experience called a "synth." Synths are meant to place you at the center of a "reconstructed" scene: You use the mouse or keyboard to move around. Unlike with video, you choose where to go next.

Say you snap a batch of pictures at the Grand Canal in Venice. Upload them to the service where the synth is automatically created (it may take awhile). Then you can pan up, down, right, left, as well as zoom in or out with images staying sharp.

Photosynth examines photos for similarities with each other and determines the vantage point they were shot and estimates the shape of the subject.

The free (for now) service was born out of Microsoft's Live Labs research. I enjoyed exploring "synths" created by Microsoft, National Geographic and others, as well as creating my own, despite prelaunch bugs. You'll need a Windows Live ID to get started. Here's a closer look:

•Taking pictures.

Shooting pictures for a synth is different from the way you'd otherwise capture images. More time consuming, too. Things that make pretty pictures do not necessarily synth well. Shooting water is problematic. Same goes for something shiny or smooth. Photosynth analyzes textures.

Microsoft says to snap two to three times the pictures you think you'll need, up to 300. Twenty pictures is the minimum. You're supposed to capture the boring bits around an object along with the presumed masterpiece. The order in which you shoot pictures doesn't matter.

Ideally, each part of a scene should be captured in at least three pictures from three different locations. You want pictures to overlap by at least 50%. Wide-angle pictures generally work best, though you'll want to mix in close-ups to capture details of portraits hanging in a museum or the prized collectibles you want to show off.

The goal is to reach a 100% "synthy" level, meaning there's a path from any one photo to another. You can view a grid to see how the pictures you uploaded are clumped together (as well as the pictures that had nothing in common with the others).

Reaching that 100% synthy level was a challenge in my tests. Still, synths at a 70% or 80% level seem to work pretty well.

I got to only a 12% level shooting 85 pictures in my backyard and 22% shooting 114 photos of a parlor in a South Carolina house I visited. The resulting synths left something to be desired.

I did better shooting a nature walk in South Carolina (55% on 73 photos) and the Soldiers' and Sailors' Monument in New York (77% on 197 photos).

It took well over an hour to upload a large batch of photos and have the software match them up.

•Viewing synths.

What you see on the screen is one perfectly rendered photo at the center, surrounded by adjacent lower-resolution, transparent and slightly blurred images, indicating pictures shot from similar places. Arrows help you navigate, but it's all still chaotic. As you move the cursor, geometric frames also appear, representing other images you've shot. Click or drag, and a new picture moves to the center, to exactly where Photosynth thinks the photographer was when it was snapped. Depending on your broadband speeds, it can take a few seconds for images to come back into focus.

On some synths, a halo helps you explore different angles. You may also see clusters of dots that Microsoft says make Photosynth more visually interesting. I found them confusing; each of these points represents where three photos intersect.

•The drawbacks.

Photosynth has elements of an unfinished research project. The "synther" works only with Windows Vista or XP machines. Microsoft says adding Mac compatibility is a top priority. You might have issues with older graphics cards. Microsoft recommends its own Internet Explorer 7 browser, though Photosynth works with Mozilla Firefox. I had a few snags testing Photosynth on Firefox. And the interface for exploring synths could be more intuitive.

My biggest beef involves privacy. You can't limit who sees your synth. All synths are public. As with YouTube or Flickr, folks can leave comments. Privacy controls are in the works.

Microsoft acknowledges there's work to be done; the company isn't sure whether to call Photosynth a "beta" or 1.0 release. Still, even with its limitations, Photosynth is worth a visit.

E-mail: ebaig@usatoday.com