The lenses have a coating to further prevent glare, and another to prevent smudging. The acetate frames have a nice heft to them—they're slightly heavier than Ray-Ban Wayfarers, but less chunky ...

\(power \ of \ a \ lens \ (D) = \frac{1}{focal \ length \ (m)}\) A lens has a power of -3.33 dioptres. Calculate the focal length and state what type of lens it is.

There are even images shot with lenses originally designed for vintage cinema projectors, x-ray machines, aerial reconnaissance and military tanks.