This custom 'hyperfisheye' lens can see behind itself
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.