Any landscape photographer has a polarizing filter in the bag. It is said that this filter reduces the reflections and helps you achieve the most beautiful sky. But how exactly does this filter work? It’s all about the physics.
The light reflected by a non-metallic surface, sunlight included, is polarized. This means, in physics’ terms, that the light waves have a specific geometrical orientation of the oscillations. To reduce the polarized light, the filter allows to pass only the light polarized in the perpendicular direction. This is what a linear polarizing filter does. You can reduce polarized light by simply rotating the filter until you reach the perfect picture.
A circular polarizing filter is a linear polarizing filter with a twist. It has a quarter wave plate glued to the linear filter. The light emerging from this plate is circularly polarized. This feature enables the circular polarizing filter to reduce the reflections coming from the mirror of your camera. Some DSLRs fix this problem by themselves, some do not. Read your camera’s manual and find out if you need to spend more on a circular polarizing filter or if a simple linear one is enough. You can still use a circular polarizing filter on a camera that does not need it. No negative effects will appear.
When to use a polarizing filter
The usual situations that need polarizing filters are photographing windows, glass, water, sky, mirrors, and so on. If you would like to photograph a Faberge egg in a museum, you will need a polarizing filter to be sure that you’ll see the actual egg in your photo and not just some strange blink from the glass box that protects it.
Polarizing filters are best known for their blue sky effect. In landscape photography, a major role is given to the sky. But if you have a clear sky, with no clouds, and no contrast, there is a chance to ruin the exposure and have an almost colorless sky. A polarizing filter will increase contrast, strengthen the colors, and offer the perfect conditions. It will also reduce haze.
Polarizing filters work well on waterfalls and large areas of water too. The colors will be intensified and the water’s reflections removed. The filter will also help reduce the glare on the vegetation around the waterfall.
How to use a polarizing filter
The filter has to be attached to the lens like any other filter. Remember that you can overlay several filters to achieve a combined effect. The polarizing filter has to be manually rotated until you reach the optimal direction for reducing the polarized light.
What problems can you have with a polarizing filter
By reducing the amount of light, a polarizing filter will slightly decrease the shutter speed. Be careful when shooting in low light conditions to stabilize your camera and avoid blurring.
Extremely wide lenses cover a wide field of view. Using a polarizing filter with a wide lens for photographing a large portion of the sky can sometimes give you portions of lighter and darker sky or a gradient disposure of blue shades.