How, Why, and When to Use Polarizing Filters

Polarizing filters are one of the most useful accessories a photographer can own. They are small, inexpensive, and make a significant impact on your photos.

Post-processing allows you to make many alterations to the photos you take. But no post-processing software can mimic the effect of polarizing filters. Using a polarizer cuts down on reflections, haze, and scattered light. They also boost color saturation and contrast.

Many imaging programs have tools to control color saturation and contrast easily and effectively. Some have dehazing tools. But none (so far) have the ability to remove glare and reflections the same as polarizing filters can.

What is a polarizing filter?

The most common polarizing filters are circular and consist of two glass pieces sandwiched together. They go on the front of your lens, so you need the correct size to fit your lens diameter (or an adaptor).

Once the filter is on the lens, you can rotate the outer layer of the filter. As you turn the filter, the effect it has on light entering your lens changes. At different angles of rotation, the amount of light that’s filtered out will vary. This depends on where the sun is and which direction you’re pointing your camera.

The most noticeable effect of a polarizing filter is when it’s rotated at a ninety-degree angle to the sun.

Here, you can see the effect the polarizing filter has on the reflection of the wood surface it is resting on. The glare coming off the wood is almost totally removed by the filter.

Why polarizing filters are useful

At times, reflections can enhance a photograph or even be the main subject. But they can also be unwanted and distracting.

When you are photographing:

• glass
• chrome
• water
• or other reflective surfaces

it can be challenging to create a clear representation in your photos. Reflections from these types of surfaces can invade your composition. They are not always possible to avoid without using a polarizing filter. Even with a polarizing filter, you may not be able to completely eliminate reflections from a surface.

Skies and clouds photographed with a polarizing filter can take on a whole different look. Compare the two images below. For the first one I used a polarizer, and for the second one I did not.

Neither image was post-processed. You can see the difference in the detail of the clouds and in the saturation of the blue sky.

When photographing at the beach or beside a lake, a polarizing filter is especially useful. Being able to control the strength of reflection in the water makes a significant difference in your photos. The added saturation boost also makes water and skies look more appealing.

How to use circular polarizing filters

Polarizing filters work by stopping some light waves from entering your lens. Light waves reflect off uneven surfaces in different directions. A polarizing filter only allows light to enter the lens that’s coming from certain directions.

As light waves vibrate and bounce off different surfaces, the direction and rate of the vibration is altered. This is why colors are also affected by polarizing filters.

When light reflects off a flat surface, using a polarizer will have a more uniform effect on it. This is because the waves are primarily moving in a similar direction. So the reflection of a window will be influenced differently by a polarizer than that of a surface that’s not flat.

When the reflected light reaches the filter, some of the waves will be blocked from entering the lens by the coating on the filter. This dichroic coating has chains of molecules lined up in one direction. Waves of light parallel to these chains are blocked by the filter.

As you rotate the outer ring of a polarizer, you can see how the effect of the filter changes. This is because you are altering the direction of the lines of the filter coating in relation to the light waves.

Putting it into practice

Using a polarizing filter is best done by turning the filter and observing what’s happening. Either by looking through your viewfinder or at your rear LCD screen, you will see the image changing as you turn the filter.

There are techniques you can read about that rely on scientific breakdowns of how these filters work. They will tell you in which direction you’ll see the most effect. But, in reality, every scene you photograph is different. It is impossible to predict correctly how the light gets blocked by the filter.

If you use a polarizer often, you’ll get more used to how it works and how you can use it to manage reflections in your photos. At times, you’ll be able to virtually eliminate reflections; in other situations, the filter will make little difference.

Conclusion

Experimenting with polarizing filters is the best way to make use of them. I usually carry a few in my bag of varying sizes. These fit my 55mm, 35mm, and 105mm lenses, which are the lenses I use the most.

Using a polarizer with a wide-angle lens can create some weird results because of the broad field of view.

If you’re making a series of photos to stitch together as a panorama, take your polarizer off. The edges of your photos may not join seamlessly if you’re using a polarizer.

Remember to attach polarizing filters to your lenses when you want to boost the color of a blue sky or reduce the reflection off a shiny surface. As you’re getting used to using this filter, take some photos of each scene with and without the filter.

That way, you’ll quickly begin to get a feel for the differences it makes.