Undoing the Polarizer

The polarizer is a glass that filters off light from one particular plane. It is generally called 'polarizer' or 'polarizing filter'.

It can be used in photography to avoid reflections that cause original colors to be suppressed by bright light. In some photographic situations, where the sun light can render harsh white washing output the polarizer can be handy.

The right situation where you would use a polarizer:

1) Window glass reflections. Where the window's reflection of objects in the photographer's side becomes obtrusive in the photo.

2) Photos in clear water ponds or stream, where skyline reflection creates haze or glittering surface. Or When you want to take photos of fishes or alligators inside water

3) deep colored objects in sunlight. Say a rose or morning glory. The flower's petals could reflect the sunlight harshly, creating non-deep, lighter color surface at some angles. Polarizer can cut off the reflection resulting in well saturated, deep colored photos.

In above situations the polarizer can cut off the reflection in one plane and let the photographer to avoid the unwanted light. The example below illustrates how to cut off reflection from blue sky. The first photo was bare lens ; and second one using polarizer correctly*:

( both photos by Kargil Jay in Blue Bell, Philadelphia; fall 2010, copyright )

Though the polarizer did the job perfectly removing blue sky especially from bottom half of the photo, neither there was a fish or white sand underwater to highlight the effect.

* correctly : Fitting the polarizer in front of the camera alone is not going to help. We have to rotate the filter correctly to the angle of sunlight (or any light). Because the polarizer (any polarizer) can cut off only one plane of the light. If you watch the Polarizer glass the inner side of the rim you will see two 'cut marks' opposite to each other . If we sketch straight line like diameter, that is the plane of light which is cut off by the polarizer. And draw more lines in either side parallel to this lines.. All these lines define the plane whose light being filtered away by the polarizer. To find these poles you can do this: keep the polarizer in front of LCD of your laptop, and look thru it, while rotating the filter. At one point the polarizer will totally blackout the screen. That plane is the polarizing plane. In the polarizer photo shown in the top of this page, you can see the 'cut mark' in inner rim at 2'o clock position. That is defines the polarizing plane. When you shoot, that cut mark should be parallel to the on coming lights plane, in order to cut off that light.

Leaving the polarizer in camera forever, is not a good idea except for bright situations. Use it when you need it. Sometimes, undoing the polarizer, can be useful. Especially when you consider reflections add elements to photo. In the photo below, I removed polarizer, because the reflections are the sole subject of this photo :

Notes:

1) Circular polarizer does not mean 'several planes'. All polarizer glasses intend to filter only one plane of light.

2) small point and shoot cameras will not fit any polarizer unless, screw-able threads are present in the front of the lens.

3) The width of polarizer filter vary and hence we must choose 52mm,64mm or whatever the camera's thread size before purchasing. The one shown about is 72 mm suitable for SLR lenses only.

4) Generally all polarizers work decently and any decent brand is ok.