You can take some absolutely gorgeous photos using the natural reflection that appears in people's and animals' eyes. With the right angle and lighting, you can even see a detailed picture of what the subject was looking at when the photo was taken.
Photo by Martin Cathrae
The problem is that in order for this to work, the photo usually has to be taken under the right conditions and fairly close up. But researchers at Columbia University have found a way to change that with their "World in an Eye" project, which can extract the images reflected on eyes in photographs even when they aren't easy to see. It's a lot more difficult than it sounds, though.
Basically, the eye and the camera form what's called a catadioptric system, which is a fancy way of saying that the eye acts as a mirror to the camera lens. The researchers used a geometric model of the cornea and some really complicated equations to comes up with a way to flatten the image of the reflection, even if the eye isn't looking directly at the camera.
They were even able to do it with old, black and white photos from around 1840.
The system works for video, too.
The images are a little blurry, but it's still impressive. You can visit the project page for a more detailed explanation of how the system works. The software isn't available for commercial use, but if you're using it for research or educational purposes you can request a copy.
Obviously, the results probably wouldn't look like these, but you could try zooming in on some of your own photos to see if you can see anything cool reflected in the subjects' eyes, or create your own reflections in Photoshop. Want to learn how to take reflective photos? Check out this tutorial and be sure to let us know how they turn out!