Friday, 3 August 2012

Polarizing Filter

Polarizing filters are the single most important piece of equipment a professional photographer needs in his arsenal. This is one filter whose effects cannot be duplicated in any stage or level of post processing. This Makes them invaluable to outdoor photographers. To those photographers who mainly shoot indoors, they are useful to cut reflections and glare.

Circular Polarizing Filter
Circular Polarizing Filter

How do Polarizing Filters Work?

Polarizing filters are placed in front of the camera lens. Unlike other filters, polarisers affect the physical characteristics of light and not its colour. They filter out light which has been directly reflected toward the camera lens at specific angles. Light from the sun spreads in waves in all directions, but light waves reflecting off a smooth surface tend to be oriented in the plane of that surface. The polarizing filter has a molecular or crystalline structure that lets light through at one angle, but restricts light from other angles. Further the filter can be rotated to change angles to block most of the reflected light. As a result when using polarizing filters Colours will be more saturated and reflections from metallic or water surfaces are either eliminated or reduced. The strength of polarization effect can be controlled by changing the camera's line of sight relative to the sun. Important thing to remember here is that the polariser must be orientated correctly to work.

Circular Vs Linear Polarisers

There are two types of polarizing filters available linear and circular. Linear polarisers are more effective and less expensive than circular ones. But as light coming through this will be linearly polarized, it renders either the metering or the autofocus ineffective. So in order to take full advantage of the capabilities of your modern day DSLR it is better to use Circular Polarizing Filter (CPL) .
Effect of Using Polarizing Filters

The advantages of using polarizing filters over your camera lens are many. The most important among them are;

  1.     Increased Colour Saturation
  2.     Eliminating or Reducing Unwanted Reflections
  3.     Control Contrast and Glare in Photographs

Effect of Circular Polarizing filter on Water

Polarizing filters are mostly used to shoot highly reflective surfaces like glass and water, when shooting water a polarizing filter enables you to completely eliminate the reflections and actually see through the water, (see clearly what is below and not just the water surface).

Effect of Circular Polarizing filter on Sky

When used to photograph sky, a polarizing filter will give a dark blue colour to the sky, bringing out cloud details and reducing the foggy, bleached out feel.

Effect of Circular Polarizing filter on Colour

As the polarizing filters cut down on reflections, they bring in more detail and with it more colour, the effect is more pronounced on shinier surfaces rather than surfaces with a matt finish or texture. Foliage often seems much greener when a filter is used.

Disadvantages of the Polarizing Filter

Polarizing filters are very expensive piece of equipment to own, the ones manufactured by reputed brands cost nearly as much as an ordinary lens will cost. They work by filtering light so in effect they are reducing the amount of light actually reaching the lens, there could be a 2 – 3 stops reduction in exposure when the filters are used. They could slow down the cameras autofocus systems and could make manual focusing even more difficult due to a darkened view finder. It takes longer to compose and shoot as they need to be rotated to precisely align them. For them to have the most impact the camera need to be pointed at a right angle to the sun else they have less effect. One major disadvantage is that they cannot be used with stitched panoramic photos. As each panel will be unevenly polarized and so the skies will not match across frames.

The convenience and possibilities with this filter is endless so as to ignore whatever drawbacks it has. So it is definitely a must buy if you wish to be a professional photographer. A general advice applicable when buying any filter is to buy the filter with thread size that matches your largest lens and buy cheap step down rings to use the filter with smaller lenses; this way you could do with just one filter for all your lenses.

In the next article we will discuss about Photography - Types of Light - Natural Light

Related Reading

  1. Graduated Neutral Density Filter
  2. Neutral Density Filter
  3. UV or Haze Filter
  4. Clamp
  5. Scrim