The big picture: The massive lens features a fully mechanical design - no image stabilizers, focus motors, etc. Even still, it's incredibly complex and to think that someone built it from scratch is mind-blowing.

The photography geeks over at Lens Rentals recently constructed a prototype fisheye lens that offers a ridiculous 270-degree field of view. Fortunately, they were kind enough to detail the build in a blog post and accompanying time-lapse video.

Lens Rentals founder Roger Cicala said the closest thing that has existed to this is the Nikkor 6mm f/2.8 fisheye, a lens from the 1970s that produces a 220-degree field of view and commands well over $100,000. This new lens, a C-4 Optics 4.9mm f/3.5 circular fisheye, has a 270-degree field of view which means it can literally see behind itself.

It should also be far sharper, have less vignetting and distortion and cost significantly less than the Nikkor.

The time-lapse is fascinating but if you're a hardcore optics geek, I'd suggest clicking over to Lens Rentals and checking out the full build log. It's incredibly detailed with loads of photos to drool over.

As one of two prototypes, the lens will probably never be offered to rent.

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All media courtesy Lens Rentals