I have often mentioned filters in this column, and there are many which can
produce some spectacular images. However, many of them can also be duplicated
post-camera with one of the programs such as Photoshop. However, a polarized
image is not something that can be done later.
The polarizing filter is needed at the time of taking the
shot, not later. There is no other filter that can make such a difference to
your final pictures, especially in the bright sun of Thailand. Once you become
used to polarized effects, you will want to leave the filter screwed on the end
of your lenses forever!
These filters are different from most others in the fact that
they are made up of two distinct elements. There is an outer ring that rotates
the outer “glass” relative to the inner element. This increases or reduces the
degree of polarization to allow the photographer an endless range of polarized
effects from one filter.
The principal behind these filters is to remove reflections,
and funnily enough it is reflections that take the color out of color
photography. Look at the surface of a swimming pool, for example - a shiny
white, non-transparent surface. Now look through a polarizing filter and you can
see right down to the tiles on the bottom of the pool. And the people frolicking
in the pool!
What happens is that these filters remove reflections from
any surface, not just water. The reason you cannot see through some normally
transparent windows is because of reflected images on the surface of the glass.
The reason some tree leaves appear to lose their color is through reflected
light from the sky above.
One of the traps for young photographers is that because you
know the grass is green, you see it as green when you look through the camera
lens - even though it is not truly green, caused by reflections. Look again at
the scene in the viewfinder. The green grass is really a mixture of green and
silvery reflections, dark shadows and pale green shoots. Put the polarizing
filter on the lens and slowly rotate the outer ring. Suddenly the silvery
reflections disappear and become a deep, solid green color. The grass is now
made up of green, dark green and pale green. This green will really leap out at
you and smack you fair between the eyes!
Your next beach scene when taken with a polarizer will really
amaze you. Again, slowly rotate the outer ring on the polarizer. Look critically
through the viewfinder and you will see the sky take on a much deeper color to
highlight the white clouds. Keep turning that outer ring and the sea will change
to a deep blue to green luminescent hue. The end result is at your command. Try
taking the same shot this weekend, but with varying degrees of polarization and
see the differences in the final shots.
Another shot to try with or without polarization is
photographing a reflective, shiny object like your family car. Again, by looking
critically through the viewfinder you will see what happens when you remove the
reflections from the paintwork.
So, if the polarizer is such a wonderful bit of gear, why do
we not make it a standard piece of equipment on all cameras? Well, like
everything, there is a downside as well as the upside. In the case of the
polarizer it does its bit of brilliance at the expense of the amount of light
that gets into the camera. With most polarizing filters you will lose about one
and a half to two stops of light. What this means is that the shutter speed will
be at least twice as long to record the same scene, or that the aperture will
have to be twice the size. This means that you are more likely to get camera
shake effects and suffer from lack of depth of field when using the polarizer.
Another drawback is that the light drop can confuse the camera’s flash settings,
so compensation has to be made for night shots.
However, if you haven’t got one - get one and see the full bodied difference
a polarizer can make!