In this article I will discuss what a polarizer filter is, and how, when and why to use it!
Polarizer filters are always circular, and therefore must be obtained in the correct size for your lens. Unlike most filters, they have a rotating front, which allows you to vary the effect. Polarizer filters remove light moving in a particular direction, and therefore they reduce reflections on non metallic surfaces such as water and glass, and increase saturation, especially in foliage and blue skies. Polarizers can be ued for shooting both in colour, and monochrome. Do note, they will make skies appear darker in monochrome mode.
Linear vs Circular?
Polarizer filters come in two types: linear and circular. Linear is more effective, and also cheaper, but circular polarizer filters are required for almost all camera’s with through-the-lens (TTL) metering, and/or autofocus! Polarizing filter remove light that moves in certain directions: Linear polarizing filters remove linearly polarizing light (moves in lines) and Circular polarizing filters remove unruly light, causing it to become circularly polarized circularly polarized light (rays of light that move outwards, moving circularly as a whole)
Linear polarizing filters can be divided into two groups: Absorbative polarizers and Beam-Splitting polarizers. The former absorbs unwanted polarization states, the latter splits unpolarized beams into two beams with oposing polarization states.
The cheapest way to create circular polarization is to place a quarter wave plate after a linear polarizer. The unruly, unpolarized light arrives, but is straightened out after being subjected to its first obstacle. The circular polarizer then forces it to move outwards, moving circularly as a whole.
Polarizer filters are not perfect. The polarization effect varies continuously, and with a wide angle lens, this is visible, due to the extremely large angle of view! If you like the effect, go ahead and use it, but it is not advised for certain purposes, such as stock photography, etcetera.
So, they increase saturation, they remove reflections, and they create interesting effect (with wide angle lenses.) Put your hands together for polarizer filters!