Photographing Rainbow Eyes By Using Birefringence
One of the many fascinating effects of cross-polarization is called “birefringence”, which is responsible for the psychedelic gradients in the seen here.
Cross Polarization: What It Is and Why It Matters
Cross polarization is a technique that uses two polarizing filters - one on the light source and on e on the camera lens - to get rid of unwanted specular reflections.