I have never been able to do this. As per the photographer’s instructions you should sit 2-3 feet from a monitor and gently cross your eyes. This will cause the two images to become three, and the middle one should be in 3D. I simply cannot cross my eyes, though I remember doing it as a kid and being told not to. Attempting to cross my eyes now makes my head hurt and stomach churn. Still, it looks like it should work for most people. More of this stuff from a fellow NYC flâneur, -ytf-, at their Flickr photostream.
