Polarizing filter (photography)

Since reflections (and sky-light) tend to be at least partially linearly-polarized, a linear polarizer can be used to change the balance of the light in the photograph.

Light reflected from a non-metallic surface becomes polarized; this effect is maximum at Brewster's angle, about 56° from the vertical for common glass.

[4] Perpendicularly incident light waves tend to reduce clarity and saturation of certain colors, which increases haziness.

The polarizing lens effectively absorbs these light waves, rendering outdoor scenes crisper with deeper color tones in subject matter such as blue skies, bodies of water and foliage.

They are mounted in a rotating collar for this purpose; one need not screw or unscrew the filter to adjust the effect.

But the metering and auto-focus sensors in certain cameras, including virtually all auto-focus single-lens reflex cameras (SLRs), will not work properly with linear polarizers because the beam splitters used to split off the light for focusing and metering are polarization-dependent.

Polarizing filters can be used deliberately to reduce available light and allow use of wider apertures to shorten depth of field for certain focus effects.

Some companies make adjustable neutral density filters by having two linear polarizing layers.