3-D effects may require one eye only
Peering through a peephole can bring flat images to life
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2013/10/js_3d_free.png?fit=860%2C460&ssl=1)
3D VISION Photos take on three dimensions when viewed through a small hole with one eye. The effect is conventionally thought to require two eyes.
Illustration: E. Otwell; photo inset: Ogphoto/iStockphoto