Canon has posted a great article with some facts you may not know about making Canon's L lenses at the Utsunomiya factory in Japan.
Below are the facts covered in the article, and I'll play spoiler on number 8…. it's telephoto lenses like the EF 100-400mm f/4.5-5.6L IS II.
- Japanese engineering is everywhere
- Lens experts can hear faults
- Lens polishing tools are made with diamonds
- Aspherical lenses are made by melting glass
- Sci-fi robots roam the factory
- Lens polishing machines self-correct
- Lens measurements are incredibly precise
- The hardest lens to make is…
- The innovation never ends
- Canon lenses could (probably) cover half the world
Number 2 is probably the most interesting fact that I didn't know.
While much of the lens manufacturing process is automated, expert craftsmen, called Takumi, play an important role in lens creation. Toshi Saito, one of Canon's lens Takumis, brings over 25 years of experience, skill and even his senses to the role. “When the lens is touching the diamond plate I know what sound it should make, so when it's slightly off, I can detect it with my hearing,” he says.
You can read the full article over at Canon Europe.