Lensrentals.com, more noteably Roger and Aaron have been working on this crazy fisheye lens for quite some time. They've now posted an article and video about the assembly of the C-4 Optics 4.9mm f/3.5 fisheye with a 270-degree field of view. You read that correctly, this lens can see behind itself.
From the Lensrentals.com:
You guys have watched us gut a lot of lenses and cameras over the years. So I thought it would be fun for you to see us put one together from scratch. Compared to many of the lenses we’ve taken apart, this is all mechanical lens is rather simple: no focus motors, image stabilizers, etc. But even a simple lens is a very complex structure. This post will probably give you a good idea of how much mechanical design is required to make even a very basic lens.
The lens is also unique; it’s a prototype C-4 Optics 4.9mm f/3.5 circular fisheye. It’s a massive lens giving a 270-degree field of view, meant for immersive video and specialty shots. To give you an idea of what 270 degrees means, the lens sees behind itself. An ultra-wide 15mm fisheye lens gives a 180-degree field of view while an 11mm rectilinear lens is less than 120 degrees. Read the full article
The retail price for this lens? Likely into 5 figure territory.
https://www.lensrentals.com/blog/2015/04/announcing-c-4-precision-optics/
It sounds like a funny experiment on zenmax and now real.
Now I wanna see a 150 f1.0 :-D
Aha! Found it. 6mm f/2.8 Nikkor with 220 degree FoV