Eventually, your photosynth is given a “synthiness” score, meaning the degree of recognizable overlap. The synthiness determines how seamlessly your 3-D panorama flows from view to view. (See Pogue's television review of Photosynth, at left.)
You can also walk completely around a stationary object, taking at least 24 photos during your circumnavigation. Later, you can rotate that object online using a doughnut-shaped scroll bar.
Once you’ve transferred the photos to your PC, you sign in to Photosynth; bizarrely, you need both a Microsoft Passport account and a Photosynth account, both free. Then you click the Create Photosynth button. Technically, your PC, not the Web site, does the analysis to knit all of those photos together, so the speed of the analysis-and-uploading process depends on your computer’s horsepower.
When it’s all over, your photosynth is live on the Web, visible for all to see. (In this version, you can’t create private photosynths.)
Amazingly, the software figures out how your photos relate, even though they’re taken at different angles, zoom amounts, exposures and so on.
It’s also amazing how, when you’re exploring the resulting photosynth, the full resolution of the original photos is available. You can zoom in, and in, and in, revealing more and more detail along the way, without ever waiting for even the biggest photo files to “load.” In one example on the Photosynth site, you start in the marbled gallery of the National Archives building in Washington — and you can zoom all the way in to the words “We the People” on the Constitution in its display case.
(This is one crucial difference between Photosynth and Apple’s QuickTime VR, which has been around for years. You can zoom in slightly in a QuickTime scene, but you can’t fly nearly infinitely into one of the component photos. Other differences: Making a QuickTime VR scene requires a special, 360-degree tripod apparatus and commercial software. And a QuickTime VR scene is rooted to one spot; you can’t freely walk through a space, as you can with Photosynth.)
So yes, it’s amazing. But in its current version (“call it beta, call it 1.0, call it whatever you want,” as the Web site puts it), Photosynth is also very frustrating.