What is the purpose of a polarizing filter in photography?

If you are passionate about photography and travel (and, if you’re looking at my blog, the chances are that you are!), you have probably heard about polarizing filters in photography, am I right? Perhaps you know all about them, maybe even without realizing it. Have you ever come across a photograph and noticed the contrasts of the colors in a blue sky, a reflection in the water (perhaps of a landscape) or a reflection in a mirror? They used a polarizing filter! So are you wondering what a polarizing filter is used for? This article is the first in a series of three dedicated to the polarizing filter in photography. The other two will help you choose a polarizing filter and learn how to use one.

In my opinion, the polarizing filter is an essential part of your photography equipment or photography accessories (along with a camera bag, a neutral filter (ND) and a tripod). It is certainly essential for all people wanting to learn about photography, especially those who want to focus on digital landscape photography.

The purpose of this article is to explain in detail the usefulness of this filter in photography. In my opinion, all travel photography enthusiasts, especially those who are interested in landscape photography, should have one! Keep in mind one very important thing, the effect of a polarizing filter cannot be reproduced in post-processing (computer post-production). The retouching of your photograph will therefore be minimal compared to one taken without a polarizing filter.

A polarizing filter (also commonly called a “pola”), is, as its name suggests, a photographic filter which is placed in front of the lens of your camera allowing the photographer to obtain certain specific effects when shooting a picture. In most cases, you will be using a circular polarizing filter (CPL). The filter changes the light of the scene being photographed, i.e. darkens it, removes glare, etc. These filters are simply threaded onto the lens of your camera (i.e. screwed on) like you would a uv filter, for example. Once you’ve finished with the filter, simply unscrew it, clean it with a cloth and store it. Square polarizing filters also exist however these are used with a filter holder that is placed in front of the camera lens.

It is important to know that there are polarizing filters for all lenses, whether you are using a Canon or Nikon or any other brand of lens (Sigma, Zeiss, Tamron, etc.). It is the diameter of the lens that will initially determine your choice of lens, and then you will look at the quality of the filter, thickness, brand, etc. Fortunately, adapter rings are available helping you to avoid buying multiple filters.

The objective of the polarizing filter is to vary the light and its power by passing it through the filter before it reaches your camera lens. Of all the filters that exist, the polarizing filter is one of the most useful, especially in the middle of the day when natural light can be very strong.

At the bottom of this article, you will find a link to my other articles which give you a selection of the different types of filters available, and especially one telling you how to choose a polarizing filter depending on your needs. The most important thing I want to show you today is how much using a polarizing filter significantly improves your photos and thereby convince you to take a chance and try one for your everyday photos and, of course, while you’re traveling.

The polarizing filter has many advantages. However, there are also some disadvantages. It is important to consider both the pros and cons before you think about buying and using one.

In this paragraph, I refer to all the advantages of using a polarizing filter. This should help you understand what a polarizing filter is for and how you can use it to take better quality photos!

1 – Make the colors explode: if I had to answer the question “what is the purpose of a polarizing filter”, the first thing I would say is that it’s to make the colors stand out. These filters increase the contrasts of a scene and also saturate the colors making them clearer. This is particularly shown when photographing waves in the sea, mountains, waterfalls, huge skies, etc. Reflections in a photo are either accentuated or removed and the colors are magnified. The saturation of the scene then makes it possible to make the blue in the sky or lagoon blaze, or the green of the leaves of the trees pop.

In general, the polarizing filter is widely used to make your skies bluer and increase the contrasts and volumes of skies.

2 – Remove reflections: this is the second most favorable point of using a polarizing filter, also sometimes referred to as an anti-reflection filter. Personally, this was one of the reasons I bought my two filters. So what reflections are we talking about here?

To suppress or reduce reflections on water: this is the most obvious and is noticeable when adjusting (rotating) the filter. Depending on the time of the day, and most particularly in broad daylight, landscape scenes which include water are particularly subject to reflections. Whether in rivers, the sea or on ice, the polarizing filter makes it possible to reduce or even eliminate the reflections in a photo. Do you still doubt its usefulness? Look at the pictures below without and with a polarizing filter, stunning don’t you think?!

You can see how the photo taken with a filter has better highlights in the lagoon and how its color stands out much better than on the photo taken without a filter in which the sun is completely reflected! Note also that the picture taken with a polarizing filter is slightly darker than the other one. These filters tend to darken the scene slightly as the filters are very slightly opaque, however, they do still allow the majority of the light source to pass through. When light conditions are low, the polarizing filter tends to reduce the shutter speed of the shot i.e. slow the speed.

The effects are particularly visible in tropical areas where reflections on turquoise water and lagoons can actually spoil a picture rather than capturing the beauty of the scene! Try photographing a beautiful blue now without using a polarizing filter and you’ll see what I mean, your travel photos will be dull….

• Remove reflections on buildings (Street photography): street photographers, and in particular architectural photographers, know the purpose of a polarizing filter very well. For the majority of them, a polarizing filter is permanently attached to their lens. As with water, a polarizing filter will reduce or even eliminate completely the reflections on glass buildings, glass surfaces, and metals such as steel and iron thus the rendering is very much improved!

• Remove reflections in macro photography: one of the other positive aspects for those who practice macro photography is that these filters allow you to highlight specific details in wildlife or nature photography. Just like on water (sea, rivers, lakes) or on buildings, the reflections can be suppressed on foliage and shells. Another great advantage of a polarizing filter.

• Remove reflections in eyes in portraits: a very useful and interesting reason for using a polarizing filter if you are a portrait photographer. Reflections in the subject’s eyes can be removed!

3 – Remove the atmospheric haze: this may be unimportant for some, but if you are a landscape photographer this haze can make your photo flat, as it lacks contrast and volume. This is particularly noticeable when taking photos through windows, for example in an airplane. Those of you who have already tried know what I mean! The reflections in the window and the haze which is visible at high altitude are suppressed when using a polarizing filter. Generally, whenever you find yourself in even the smallest amount of fog, haze (in the mountains for example), the polarizer will be very useful to you!

4 – Help for long exposures: while this is not the primary purpose of a polarizing filter, it does absorb light and therefore it may be useful if you want to slow down your exposure time (for long exposure photos, for example) but don’t have an ND filter (neutral density filter) on hand. The polarizing filter, in addition to suppressing reflections, will also allow you to expose the scene for a longer due to its opacity.

5 – Protection of your optics: this is the last advantage in my opinion, and not the most obvious one. A polarizing filter will protect your lens from dust and dirt, and even protect it in the event of a fall! The filter, therefore, also plays a protective role as it’s better to break your polarizing filter, even if it did cost 100€, than your lens which probably cost around 1000€, am I right?!

Well, I hope I’ve shown you all the advantages of using a polarizing filter. You don’t need to have been a professional photographer for many years to understand how it works, any amateur photographer will be able to use the filter. It’s really quite simple!

The polarizing filter also has some disadvantages, mainly concerning when to use it!

• Loss of brightness: it is important to note that the presence of a polarizing filter in front of your camera lens will give you a loss of one to two diaphragms, in other words your images will be darker. I plan to discuss this further in other articles on the subject but, to put it bluntly, it means that when a polarizing filter is attached to your lens you will have less light coming through to the sensor on your camera and therefore you will see a slight darkening of your scene. To compensate for this loss of brightness, you will need to take slower pictures i.e. reduce the speed. Basically, the less light you have, the slower the speed of your shot.
  This is important to take into account when you’re trying to get a clear picture in low light with very little time.

• Difficult to handle with a lens hood: this is one of the annoying things about using a polarizing filter. Bear in mind that in most cases, the filter is almost, or completely, impossible to use with a lens hood. The size of the lens hood, and especially its depth, makes it impossible to use with most polarizing filters. This is certainly a problem I have when using my polarizing filter.

• Vignetting at certain focal lengths: another thing to take into account when using a polarizing filter is the vignetting effects on the edges of your image during shooting. In fact, the more you use wide angle (GA) or Ultra Wide Angle (UGA) lenses, the more you will see the effects of vignetting on the edges of your photos. It is important to pay particular attention to this factor when purchasing your polarizing filter. I will come back to this point in my article explaining how to choose a polarizing filter. The best way to avoid vignetting, in most cases, is to buy a Slim (fine) filter.
  

Another aspect to bear in mind when using a wide-angle lens is that there will be a variation in the brightness of your scene. You won’t have this problem with the longer lenses.

• Brightness variation: As explained above, when using wide-angle lenses to photograph large areas of sky, for example, you will see that the polarization is not uniform at the center and edges of the image, this is due to your orientation in relation to the sun and the very wide field of view of your lens,
  

• Cost: I will finish this article with this important aspect. Good quality polarizing filters are not cheap and you will have to pay for what you want! In my backpack, for example, I have my Canon 24-70 mm f/2.8 lens which has a large diameter of 82 mm. The larger the diameter, the more expensive the filter will be! My advice is to think before you buy and make sure you don’t waste money on a low-end polarizing filter of poor quality. It is better to spend a little more and be happy than be frustrated by the poor quality. Think of it as an investment!

There you are, the overall advantages and disadvantages of a polarizing filter. I hope you believe me when I say what a very useful accessory it is. And at least you no longer have to wonder what a polarizing filter is for. In my opinion, it’s one of the most essential accessories for all landscape and travel photographers!

Do bear in mind one very important point; you can’t reproduce the effects of a polarizing filter in post-processing! I am deliberately not talking about using these filters in this article as that is the subject of another one of my articles in which I explain using the filter for different photo techniques, such as photographing against the light, i. e. to position yourself in relation to the sun. This was the subject of a detailed article. I wrote a complete article on the camera lens filter, its usefulness, choices and use. If you are new to photography and want to know more about filters in general, this is the perfect post.

Would you like to know how to choose your polarizing filter? Which is the best one? Is there a good brand? I answer all these questions in a very detailed article on that very subject!

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See you soon,

Written by Sylvain PONS

I've been passionate about photography since 2010, learning as I went along. Today, I dedicate myself to guiding others in their choice of camera gear and sharing a variety of tips to improve their photography skills.

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