From the LensRentals Blog:
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.See the entire illustrated assembly at the LensRentals Blog.
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.
The closest thing that’s existed to this is the 1970s classic Nikkor 6mm f/2.8 fisheye, which gave a 220-degree field of view, weighed 5 kg, and can be rarely found for $100,000 and up these days. The C-4 optics lens weighs every bit as much as the Nikkor, but should be far sharper, have less distortion and vignetting, and cost somewhat less than those do today. (‘Somewhat’ being defined as ‘less than half’.)
So let’s put stuff together!