• Short Information


• Detailed information


• Examples

Short information

This is second article on photography filters. You can read the first one on UV photo filters.

For those of you that don't want to get too technical, here are major benefits of using polarizing filters (scroll down for examples):

• colors are more saturated


• you can get darker colors in the sky - even dark blue sky


• remove reflections from water surfaces and glass


• use it to reduce light so that you can shoot with slower shutter speeds

Detailed information on how Polarizing filters work

A physicist would say: most sources of electromagnetic radiation contain a large number of atoms or molecules that emit light. The orientation of the electric fields produced by these emitters may not be correlated, in which case the light is said to be unpolarized. Which, translated to plain English means that: almost all light is, by default, is in state that is unpolarised. Here is a illustration of unpolarised light:

When this light hits some surface, as glass or water surface - it gets reflected. Leve of reflection depends on entrance angle of the light and surface reflection qualities. Interesting part is that when the reflection occurs, very often the light is being polarized, because only one of atom generated waves is being reflected. To a naked eye - the light is the same. We can not feel any difference.

When we put a polarizing filter in front of our lens, here is what happens. Polarizes acts as filter to the polarization. It has one plane of polarization - and only light that has that plane will pass. All others are blocked. So, if we use polarizer with regular light it will pass one plane and the final image will look the same - just as we did not use any (since we cannot see the difference). However, when we use polarizing filter with polarized light, interesting thing happens. The light has one orientation of its polarization and the filter has other. When those two match - the light is passed. When they do not match - filter will block the light. Quantity of blocking depends on filter make and quality.

The filter is most effective when used at 90 angles degree from the light.

Air atoms reflect and polarize some of the light that hit them. Lets say that we are shooting some landscape. If we put on pol. filter and point the lens at 90 degree from the sun, we can benefit from darker sky. So, get the sun to your left or right shoulder and make that landscape shot with and without the filter. What happens is that the polarized light from air atoms is blocked. So, the sky itself has less light that hits the sensor and it appears darker. This is useful as usually the sky is very bright, and not so pleasant for viewers eye.

Same applies to reflected light from leaves, doors, glass, water surfaces etc

Examples

See how the filter darkens the sky, defines clouds and also makes trees little greener

Polarization filter is oned on left side. check how it removed the reflection in glass, so you can see through it

The filter has darkened the sky, and also removed reflection from sea surface so that the sea bottom is visible