Make and Slashdot discuss an interesting paper on dual photography. Dual photography “exploits Helmholtz reciprocity to interchange the lights and cameras in a scene“. In simple english, it enables you to take a picture of a scene, then view it from wherever the illuminating light source is setup.

This blows my mind. There are some impressive photos of its use in action in the full paper(pdf).

What can this be used for? To me this has obvious applications in military/paramilitary and surveilence applications. But it sure would be handy next time I play poker too.