Who in Japan have its own glassworks, that is its own glass manufacturing for lenses.
As I know Nikon, Mamiya, Hoya, and not sure for Canon are the only.
I seem to remember that the 1st World War had a huge impact on optical glass.
As Germany made all the specialist glass used in lenses, Britain and its allies were in a no win situation.
The UK Government realised the need for good optics for military use and pumped money into research. Pilkingtons are world leaders in specialist glass and supply the Japanese market.
Strange as may seem specialist glasses are blended with locally made glass to make lenses.
Who in Japan have its own glassworks, that is its own glass manufacturing for lenses.
As I know Nikon, Mamiya, Hoya, and not sure for Canon are the only.