The second-hand camera lens market is currently valued at $2.5 billion (around £2.0 billion / AU$3.9 billion), with projections suggesting a growth rate of over 5.8% between now and 2023 ...

Rather than taking individual lenses, he’s starting with the second-hand lens from an old projector. It’s got the required huge aperture, but it’s by no means a photographic lens.