If you’re doing ordinary photography and videography, there’s rarely any need to go beyond extreme wide-angle lenses — but why be ordinary? This absurd custom fisheye lens has a 270-degree field of view, meaning it can see behind the camera it’s mounted on — or rather the camera mounted on it.

It’s certainly a bit of fun from Lens Rentals, the outfit that put it together, but it’s definitely real and might even be useful. Their detailed documentation of how they put it together piece by piece is fascinating (at least I found it so) and gives an idea of how complex lens assemblies can be. Of course, this one’s not exactly standard, but still.

The C-4 Optics 4.9mm f/3.5 Hyperfisheye Prototype, as they call it (hereafter “the lens”) first appeared as what seemed at the time to be an April Fools’ joke, at best half-serious. “The Flying Saucer,” as they called it, AKA the Light Bender, AKA the Mother of all Fisheye Lenses, included a vaguely plausible optical diagram showing the path of light traveling from the far edge of its view, from about 45 degrees rearward of the camera.

Sure, why not? Because it’s ridiculous, that’s why not!

But the beautiful bastards did it anyway, and the results are as ridiculous as you’d imagine. There are lenses out there that produce past-180-degree images, but 270 is really quite beyond them. Here’s what the output looks like, raw on top and corrected below:

Naturally you wouldn’t want this for snapshots. It would be for very specific shots in high resolution that you would massage to get back to something resembling an ordinary field of view, or somehow incorporate into a VR or AR experience.

The camera has to mount in between the legs that support the lens, which is probably a rather fiddly process to undertake. The enormous lens cap, or “lens helmet,” doubles as an upside-down stand to ease the task.

It’s a fun project and adds one more weird thing (two, technically, since they built a second) to the world, so I support it wholeheartedly. Unfortunately because it’s a “passion project” it won’t be available for rent, so you’ll be stuck with something like the Nikon 6mm f/2.8, with its paltry 220-degree field of view. What’s even the point?