Recently I learned that today's lenses don't contain "just glass" as optical elements but often specially designed plastic elements too.
Here's a video by Gordon Laing showing a "Canon lens TEARDOWN! What's INSIDE a new lens?"
Here's a video by Gordon Laing showing a "Canon lens TEARDOWN! What's INSIDE a new lens?"
Replica aspherical lens elements are produced by using an aspherical surface mold and ultraviolet-light-hardening resin to form an aspherical surface layer on a spherical glass lens.