Why and How to Use a Circular Polarizer Filter

Why and How to Use a Circular Polarizer Filter

Pop on a pair of (decent) sunglasses and not only are your eyes less strained, things just look better. The reason for this is likely the polarization effect. Colors may appear more saturated, bright blue skies can take on a deeper hue, and some pesky reflections just vanish. All of these can benefit certain photographs and make the circular polarizer filter one of the best—and most difficult—filters to use. 

Exactly What Does a Polarizer Do?

It’s both simple and difficult to understand what polarizing filters accomplish. Technically, per our expert product writers, a circular polarizer “helps to reduce reflections and glare by filtering out light that has become polarized due to reflection from a non-metallic surface.” Essentially, this means it cuts down on certain types of light in a way that can benefit your imagery. More specifically, it will reduce glare and reflections, including certain haze. In real-world applications this can help eliminate reflections on glass or water, reduce some reflected light on certain subjects, or improve overall contrast in a landscape.

You may have heard of linear polarizers, in addition to the now standard circular polarizer. In practice, both filters accomplish the same goal. However, circular polarizers have an extra quarter wave-plane element that helps convert the light back into a form that is suitable for modern autofocus and auto-exposure systems. Since this tech wasn’t around years ago, early filters were fine with linear polarization, but if you are shopping today, circular is the safe bet.

A quick example of how effective a polarizer can be. The image on the left was made with the polarizer and the image on the right without.

Basic Polarizer Tips

How exactly do you best make use of a polarizer? That can be incredibly easy or extremely technical, depending on how you want to approach it. If you pick one up, you will notice that the front part of the filter spins and then changes the appearance of the image on your camera. You could very easily just make the adjustments, preview in the camera, and then just pick a position that looks the best. Simple and effective.

Technically, there are some things to know. Among the most important is that polarizers work best when at a 90° angle from the sun. This means that you should practically never use a polarizer facing directly toward the sun. Another reason to take off the filter for shots that include the sun is that the extra glass can result in more flaring. So, your sunsets and sunrise photos will be better off without the filter.

The sun is directly ahead in this shot and you can see the relative ineffectiveness of the polarizer.

Another thing to keep in mind is that polarization is not likely to have a uniform appearance across your entire image. This is especially true with wide-angle lenses. Getting a deeper blue out of a sky is a very common use for a polarizer, but if you are shooting with an ultra-wide lens you may see that the sky shifts quickly from normal to dark in an unnatural way. Be careful with the way you apply it and you shouldn’t have an issue. You have control over where and how much polarization will have an impact on your photo, so you should experiment.

While using the filter, you may notice that your camera’s meter is telling you to increase your exposure. That is because polarizers generally absorb some of the light entering the lens—it is part of their job. You can expect to lose between 1-3 stops of light, depending on the exact model and brand of filter you picked. It can result in some moments where a tripod might be advisable to get your exposure just right. It also means that polarizers are not going to be great filters for low-light situations.

A very deep blue transitions quickly to a normal sky in this image made with a wide-angle lens.

If you are looking for a recommendation, we chose the B+W XS-Pro Kaesemannn Circular Polarizer MRC-Nano Filter for our tests, and found it to be very reliable, though you should have good luck with plenty of brands on the market.

That should be all the basic information you need to get started with a polarizing filter, but if you have any questions, please feel free to ask in the Comments section, below. 

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I've used polarizers for years. They work realy great when used as directed in this article. However, the article doesn't mention being careful about the ring used to mount the polarizer to the lens. For my larger lens diameters I like to use the Cokin(R) drop-in polarizer because it doesn’t screw on to the lens. The Corkin(R) filters requires 2 additional adapters that allow the lens to slide into the filter holder. I have found that polarizer filters that screw directly onto the lens can sometimes be difficult if not impossible to remove.

B&H got the part about reflections right, however, they left out any explanation of why polarizers can produce deep blue skies.   It turns out that light scattered from tiny air molecules, the light blue "sky light" you see in the absence of clouds, is polarized.  Light scattered from the much larger water molecules in clouds is not polarized. So, a properly adjusted polarizer can reject the sky light while leaving the light from the clouds and the ground basically unchanged, leading to dark blue skies. 

Thank you for that addition information. That was helpful.