A polarizing filter is one of the most essential tools in a landscape photographer’s bag. It is typically the first filter landscape photographers buy to instantly improve their pictures and and add vividness and contrast to them. If you do not already have a polarizing filter, I highly recommend getting one for your landscape photography.
A lot of people ask me how I get the sky in my images to be so blue. While I must admit that there are many variables involved in making the sky look natural, a polarizing filter can actually make the sky look more dramatic, once you learn how to use it properly. Basically, a polarizer can reduce reflections from objects such as water and glass and can be used to darken the sky and bring out the clouds, making the scene look much more vivid. It can also help reduce haze. For all normal lenses that have a filter thread in the front, you can get a circular polarizing filter, also known as a “circular polarizer”. A circular polarizer is very easy to use and once you attach it on the front of your lens, all you need to do is rotate it clockwise or counter-clockwise to get a different amount of polarization. Polarizing filters work by blocking certain light waves from entering the lens. Rotating a polarizer allows certain types of light waves to pass through, while blocking other ranges of light waves. Thus, you could turn a sky from light blue to very dark blue or increase/decrease reflections by simply rotating the filter.
Keep in mind that time of the day plays a big role in the amount of polarization you can get from a polarizing filter. You can obtain maximum polarization when the sun is at about 37 degrees from the horizon, so if the sun is directly overhead or very close to the horizon, the effect of the polarizer will vary and in some cases you might not even see any polarization effect no matter how much you rotate the filter. The effect of polarization changes relative to the sun. The maximum effect of polarization is achieved when the lens is pointed 90 degrees from the sun (in any direction). A simple trick is to form a pistol with your index and thumb fingers, then point your index finger at the sun. Keep pointing at the sun and rotate your hand clockwise and counter-clockwise. The maximum effect of polarization will be where your thumb points in any direction. So if the sun is in front of you, or directly behind you close to the horizon, you might not see the effect of polarization on the sky at all. The polarizer can still help reduce haze and reflections, but it might not do anything to the sky. Also, you have to be very careful when using a polarizer with super wide-angle lenses (24mm and below), because the sky might not get darkened equally, resulting in a bad-looking half blue-half gray sky.
Here is an example of a bad-looking sky, as a result of incorrect usage of a polarizing filter. Basically, I pointed just a little to the right of the sun, which is why the area on the left is so light in color. Images like these with “gradient” skies are extremely hard to deal with in post-processing:
I always check my rear LCD after shooting with a circular polarizer, making sure that the sky looks the same from left to right. In the above case, I quickly understood that I made a mistake and pointed the camera to the far right, away from the sun, to darken the sky more evenly. As you can see, it makes a huge difference!
Another important factor is that a polarizing filter can help to deal with reflective surfaces. Take a look at the following two examples below. Before I shot the first image, I made sure that all of the reflections are removed from the water. The result, as you can see from the below image, is that we no longer see any natural reflections.
Compare the above to the picture below, where a circular polarizer was rotated to a minimum effect, keeping the natural reflections of the surrounding area on the water surface:
Overall, a circular polarizer is a very helpful tool in a photographer’s bag. I personally use the B+W 77mm Kaeseman circular polarizing filter, because of its high quality optics, but you can use other brands such as “Tiffen” and “Hoya” as well. Just make sure that you are buying the right size for your lens filter holder. For example, if your lens filter thread is 77mm, make sure to buy a 77mm circular polarizer. If you have multiple lenses of different sizes, I recommend buying one 77mm filter in addition to cheaper step-up rings.