Journal / 02
What 480 nanometres means
A number on a spectrum, and what the glass does with it.
Visible light runs from roughly 380 to 700 nanometres. The short end reads as violet and blue. The long end reads as red.
The amber lens absorbs most light below about 480 nm. Below 450 nm less than 1 % passes. Above roughly 500 nm it is nearly clear, so the rest of the spectrum arrives intact, a little warmer.
The curve is measured on the finished lens: steep at the short end, nearly clear beyond 500 nm. That is what the amber is.