Photo Journalism 4(1+3)

Lesson 9 : Types of Filters

Polarisers filters

The polarizing filter is one of the most useful filters for outdoor photography. It should really be in every serious photographer's camera bag.
Polarizing filters exist for most camera types, from medium format to digital point and shoot cameras. Autofocus SLRs (like the ones I use) need circular polarizers. In these, the front side rotates which enables the user to see the effect gradually appear in the viewfinder.

Polarizing filter effects
The polarizing filter has one main effect: it eliminates reflection from non metal surfaces. It is effective on:

• Skies : By eliminating the reflection of light on the tiny water droplets present in the atmosphere the polarizer brings more saturated and slighly darker skies. However this does not work from any angle. You will generally be able to assess the effect visually, especially with a SLR camera, but keep in mind that it works best with the sun at 90° from your position. With the sun in front, a polarizing filter will have no effect.

• Water and reflective surfaces : By eliminating reflections, the polarizing filter will tend to make water and other reflective surfaces more transparent. The effect will also vary depending on the angle to the reflective surface. If you place your camera very low above a river, the effect will be very limited. If you shoot from a bridge above it, the water will look totally transparent.

• Colors : The polarizing filter also reduces reflection from other surfaces such as foliage and thus makes their colors look more intense. It also tends to make shadow areas darker.

• Light absorption : The main side-effect of the polarizing filter is that it absorbs 1.5 stop of light. Thus if you shoot at 1/180th of a second and then add the filter, you will find yourself at 1/60th of a second. This happens whatever the orientation for a circular polarizer.