Get a more pro image with a polarizing filter

I recently decided to equip my camcorder with a circular polarizing filter. In certain circumstances the use of such a filter allows :

• to darken blue skies extremely bright. Blue become deeper significantly increasing the contrast with clouds
• to increase color saturation especially green. Foliage or lawns look nicer
• to reduce reflections on glass surfaces or the water surface. You will be able to shoot someone behind glass or fishes in a river or a lake

For those like me who like to understand things, I propose you at the end of the news an explanation of polarized light and the reasons of the effects on our videos of a polarizing filter.

The filter I bought is the HOYA PRO 1 DIGITAL. You can found it for about € 60 on the internet. The filter is screwed onto the camcorder lens and the outer part rotates freely to adjust its effect :

A video is better than a long explanation, here are some examples I shot during a sunny day with and without the filter (watch it full screen, 720p).

I think the benefits of the filter on the sky and greenery are striking. On the other side, for red, pink, orange or yellow hues, it is less obvious.

Some of you may have noticed a slight increase of the bokeh effect (background blur) when the filter is applied. The explanation lies in the fact that a polarizing filter darkens the picture about 2 diaphragms. The automation of the camcorder compensates for this loss of light by opening the diaphragm more. As I have a large sensor camcorder, this increased aperture immediatly leads to decrease the depth of field, where the increase in blur background.
This leads me to give a first recommendation: a polarizing filter should not be used indoors or in low light condition and especially not at night.
My other recommendation is that you must be placed perpendicular to the main light source (usually the sun), otherwise the polarizing filter will have little effect. For that, a tip: lift your thumb up and tighten your index finger perpendicular to thumb. Lay your arm. Point your thumb toward the sun. The right direction to shoot is the one pointed by your index.

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A few of theory :

We can consider the light that we see as an electromagnetic wave that vibrates in all planes around its axis of propagation. If we make an analogy with a guitar string we could say that if rubbed up and down it will vibrate in a vertical plane, if rubbed from left to right it will vibrate in a horizontal plane and if rubbed bias it will vibrate on an inclined plane. Well, imagine that instead of vibrating in a single plane it vibrates in all planes at once. This is exactly what a light wave does. Except that in some specific circumstances it vibrates in a single plane, that's what is called polarization.

A polarizing filter passes only light that passes through following a certain plan.
When light hits a non-metallic reflecting surface a greater or lesser part of the light is reflected so polarized. If this polarized light is sensed through a polarizing filter, according to its setting can prevent the light to pass therethrough. This decrease of reflected light has the immediate effect of improving color perception and the overall contrast of the image. In the sky, it is the microscopic water droplets that are in the atmosphere that serve as reflective surfaces. Only a portion of light from the sky is polarized. This is why the sky remains blue with a polarizing filter but a deeper blue.