Fisheye Lenses: From Under the Sea to Up in the Cosmos

Among photography's most well-known tools is the fisheye lens. Check out Groupon's explanation to understand how this device bends the world to its will.

To capture the entirety of the cosmos at night, it’s helpful to look at the world like a fish. That is, as if underwater. Fish, scuba divers, and other aquatic creatures will notice a curious phenomenon when they look up at the surface. Because of how light refracts on the surface of water, an entire 180-degree panorama of the world above is compressed into a bright, circular image.

This view will look familiar to anyone who’s ever seen a fisheye photograph of an entire cityscape bending into view from ground level or the comically enlarged snout of a curious dog sniffing a camera that was dropped in bacon grease. And in fact, the former inspired the latter. In 1906, inventor and physicist Robert W. Wood created a pinhole camera filled with water to capture similarly compressed-but-comprehensive panoramas, and coined the term fisheye shot to describe it.

Today’s fisheye lenses don’t need water. Instead, they use an extremely wide-angle lens with an ultra-short focal length that captures a wide slice of the visual field and dramatically bends light rays into one of two kinds of images. Circle lenses produce perfectly round images on a black background, whereas full-frame lenses yield partially rounded pictures with a bulging central focus around which all other elements curve. Beyond its use in creative photography, astronomers picked up on the fish-eye lens soon after its invention in order to capture an entire hemisphere of sky at once, and planetariums often turn the technology inside out, using fisheye projection lenses to fill a domed ceiling with sky.