100 years ago, stereoscopic photos were a bit of a novelty, showing up in coin-operated viewers that forced your eyes to see the paired pictures in 3D. Some 40,000 of those snapshots (whose copyrights have expired) are now in the New York Public Library archives. Earlier this week, NYPL Labs debuted its Stereogranimator tool that lets you resurrect the old 3D effect in animated GIFs or red and blue 3D anaglyphs.

The New York Times reports the idea was originally born in the brain of San Francisco artist and writer Joshua Heineman, who found the images in the NYPL archives and recognized them as stereographs. He spent hours looking "behind" hundreds of dual images to see them in 3D before he had the idea to simulate the effect with an animated GIF. (You can try out both methods below, but if you can get the side-by-side style to work, the effect is much better.) Heineman's activities eventually caught the library's attention, prompting creation of the tool now available to everyone.