Polarized Light Photography (PL)
Polarized light photography (PL) is a useful method for documentation of works of art and archaeology. PL photography eliminates surface reflections and professional photographers use it for high quality documentation of varnished art.
Applications in Art examination
PL photography eliminates glare in photos, in particular, disturbing reflections from varnish. Light from the lamps can be reflected or diffused from a painting. Reflected light gives glare while diffused light provides colors and texture. When the light is reflected it keeps its polarization while diffused light loses it. So, when polarized light illuminates a painting, the glare is still a polarized beam while diffused light vibrates in any direction.
Experimental Set up
A classical experiment with polarized light is that done with a calcite crystal and a polarizing filter.
For manual focus it can be used a linear polarizing filter. A circular polarizing filter is necessary for auto focus. Indeed, the camera focusing system doesn’t work properly with polarized light. The circular polarizing filter resolves this problem. It is essentially a liner polarizing filter that diffuse the polarized light just before feeding it to the camera.
A video on linear polarizing filter and circular polarizing filter: