Polarizing Filters - What You Need to Know

Have you ever noticed how wearing sunglasses reduces glare and eye strain? Or noticed that the world looks a little better – bluer skies, deeper color – when you have them on? A polarizer filer is like sunglasses for your camera lens. The reduction of reflections, increased saturation, and enhanced look to foliage and clouds make polarizers one of the must-have filters for landscape photography. It is also great for portraits and other genres of photography, but can be tricky to use.

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What is a Polarizing Filter?

A polarizing filter or circular polarizing filter is added to a lens to filter out certain light waves preventing them from entering the camera, or conversely to allow only certain light waves into the camera. The filter rotates to increase or decrease the effect. Their purpose is to filter light that has become polarized due to reflection from a non-metallic surface. When a beam of light from the sun hits a non-metallic surface (like glass, water, leaves, etc.) some light is refracted and some light is reflected. When the angle between the refracted and reflected light is perpendicular (90 degrees – this 90 degree angle is important, we will come back to this later), you create a reflection that is polarized light. Polarized light has its wave or vibration reduced to one plane (light waves normally vibrate in more than one plane). Polarized light from horizontal surfaces, such as off the hood of a car, can be blocked by wearing polarized sunglasses (they contain vertical fence like structures in the lens that block the horizontal rays and only let in the vertical ones thus reducing the glare we see). A polarizing lens for your camera has the same effect. The filter will reduce glare and reflections from subjects like glass or water, reduce some haze (polarized light from molecules in the air), and thus help improve the overall image.

What does a polarizing filter do?

First of all the effect of a polarizing filter is not something you can replicate in editing software. You cannot simulate the effect in editing. You cannot change water to be able to see through it with editing tools or sliders. You cannot remove unwanted hot spots from glare and strong reflections. This is one element that needs to be done correctly when you take the shot, or “in camera.”

Polarizing filters are very popular among landscape photographers. Since they block some light from reaching the sensor, they can be used to enhance clouds and create more interesting skies. The polarizer can be adjusted by rotating to increase or decrease the intensity of the effect. Landscapes can appear desaturated in harsh lighting (increased highlights and reduced color and detail). The polarizer will help create more saturated colors with bluer skies and whiter clouds. The glare on foliage and plants and be eliminated or lessened by using a polarizing filter. The glare on water (lakes, ponds, waterfalls) can be decreased. As you rotate the filter you can see more into and through the body of water. They can be effective in reducing glare for portraits, as well as eliminating reflections on windows allowing you to shoot through the window (increased effect) or shoot the reflection on the window (decreased effect). In a nutshell, if you want to achieve stunning landscape photos you will need a circular polarizer in your bag and you will need to learn when and how to use it. Below is an example of how effective a polarizer filter is when used properly. The first image is a pond with no polarizer. The second image is the same shot with the filter added to the lens. While the reflections are not completely removed, they are far less noticeable in the second image.

How do you use a polarizing filter?

The easiest way to use a polarizing filter is to put it on the lens and then rotate the filter until it the scene looks best. While this can be effective, a bit more knowledge can go a long way to improving your images.

For example, there is no one position or “setting” that you can rotate the polarizer to and have that be effective for every shot. It must be adjusted whenever you move or the location of the sun moves. If you take a shot with the camera held in portrait or vertical orientation and set the polarizer for the best effect and later turn the camera to horizontal or landscape orientation, the polarizer will need to be adjusted.
There are many other factors that will help you get the most out of your filter, such as knowing how the time of day and angle of the sun affects its use, the direction and angle of your shoot, whether the lens is wide angle or telephoto, whether it is overcast skies or not, and more. For example, you might put the polarizer on your lens and rotate it and nothing happens. You rotate it some more, all the way around, and nothing happens. The best place to look for changes is in the sky. There should be a noticeable color shift to a darker blue. There are times and angles where no polarized light may be entering the camera. If no polarized light is entering, then there is nothing for the filter to block. If you rotate the filter and there is no change, then take the polarizer off. It isn’t helping and it just becomes another piece of glass that could reduce your image quality.

This is where that 90 degree angle information I mentioned at the start comes in handy. Polarizing filters work best when they are at a 90 degree angle from the sun. This means a polarizer will have practically no effect when you have a photo shoot facing toward the sun. Your sunrise or sunset photos will be better without it and you also reduce the odds of flares appearing in your shots when you remove the filter. Below is an image where the camera was aimed toward the sun. In an instance like this a polarizing filter would have little or no effect.

To find the 90 degree angle where a polarizer is most effective, there is a “handy” little trick using your hand! Make a letter L or gun shape out of your hand (forefinger as the gun barrel and your thumb as the hammer) and point the “gun” toward the sun. Rotate with your wrist only and notice the direction your thumb points as you rotate around. Any direction that your thumb points is a direction you can point your camera with the polarizer for maximum effect. You are essentially creating a 90 degree angle with your forefinger and thumb. You can get off angle a little and the effect will still work somewhat, but if you get too far off you won’t see much difference with the polarizer versus without.

Something else to keep in mind, maximizing the effect with your polarizer may not always be the best option. For example, if you remove all the reflection off of a body of water, then the water may appear unnatural. Since the filter tends to increase saturation, there can be too much of a good thing in your skies too. That deeper blue can begin to appear almost black and sometimes does not appear uniformly throughout the image. The wider the angle of your lens, the more you will notice the shift in color in the sky becoming unnatural. In a case where you notice the sky getting too dark, take control over the issue and reduce the polarization by backing down and taking several shots with different levels. Keep in mind that the darkening effect is almost always more noticeable on your computer screen, than what you saw in camera. So when you think you have it right, take an image, then back down a bit and take a few more. Notice in the image below how the blues become very dark near the top of the frame.

Another aspect of using a polarizer that you should be aware of is the decrease in exposure it creates. When the filter is in place, it acts like sunglasses. When you put on sunglasses, everything gets a bit darker, right? The same applies to the camera. When you add the filter, the amount of light hitting the sensor is reduced. The amount of loss of light will depend on the filter you buy, but most lose at least one stop of light (and some up to three stops). Therefore, a polarizing filter is not a good choice when you have a low-light situation. It also means you may have to open your aperture, increase your ISO, or decrease your shutter speed to get proper exposure. If you are in auto shooting modes the camera will do this automatically to compensate. A decrease in shutter speed may then require a tripod to avoid camera shake. If you are not familiar with the exposure triangle and stops of light, you might want to read some of our previous posts on the exposure triangle and ISO, or our lessons on aperture and shutter speed. In a pinch, a polarizer can be used as a low level ND (neutral density) filter. Be sure to check out next month's post in the filter series which will cover ND filters.

A polarizer will not alleviate the need for multiple exposures or post processing. While a polarizer can greatly improve a landscape photo, there may be times where you still need to take an image with exposure on the foreground and an image with exposure on the mid or background (or sky) which are then blended. If you are taking a photo of a waterfall, you might want the reflection on some of the rocks that are out of the water, but remove the reflections on the pools of water. You would still need to take multiple images that are later blended in editing.

Vignetting is another common issue with polarizing filters. Wide apertures (which are commonly used for landscape photos) and wide angle lenses can increase this effect. The vignette issue varies greatly among brands, so carefully read reviews. A slim or thin polarizer may help prevent the vignette on a wide angle lens. The vignetting effect and darkening effect mentioned previously, also mean that polarizers are not a great option for a panorama. As you move across the panorama, your angle from the sun will change and the colors in the sky can look unnatural. If you plan to take a series of images that stitch together in editing, you may find it impossible to line up and match the colors of the sky from one image to the next in the sequence. In the image below the sky gets noticeably darker towards the right side of the panorama as the angle from the sun changes.

While maximizing the effect of polarizer can saturate colors in a traditional landscape photo, it does the opposite effect on a rainbow! Rainbows are caused by reflections, so if you rotate the polarizer to increase the glare (minimize the effect of the polarizer), you will see a more colorful rainbow. If you rotate to decrease the glare (maximize the effect of the polarizer), the rainbow may almost disappear from view.

One final suggestion for getting the most from your polarizer is to change the metering on your camera from matrix/evaluative to center-weighted (preferable, if it is an option) or spot metering. Then point and meter off of a mid-tone to set your exposure. If you need more information about metering, we have an Ultimate Photography Cheat Sheet with metering plus 11 other common photography concepts on our Etsy store for only $4 and we've covered some of the basics in this previous blog post. 

What should I look for when buying a circular polarizer?

Don’t buy cheap. A quality filter is important. A quality filter will have the polarizing material bonded and sandwiched between layers of glass for better optical quality (no air bubbles or irregularities). The optic should be good glass (not plastic) and look for one with multi-coating. Uncoated filters can cause ghosting and flares. The retaining rings should be brass (strongest), or at the least aluminum (which can jam and dent more easily), and never plastic.

You will need the size that fits your lens. The diameter of your lens should be indicated on the end of the lens or on the lens cap with a number and a lower case letter o with a line through it or in millimeters (not to be confused with focal length). You will need to purchase a filter that is the same size, or purchase an oversized filter and step up rings so you can use the filter on all of your lenses (instead of buying a filter for every lens). For example, if you have Nikon lenses in 52mm, 72mm, and 77mm instead of buying three filters (one for each), you can purchase one filter in the 77mm size then use the step up rings when you need to use it with the 52m or 72mm lenses.

When doing your shopping you may encounter linear polarizing filters. Linear and circular polarizers perform almost identically. Circular polarizers are designed for use with autofocus lenses (but can be used with manual focus lenses with the same results). Linear polarizers are designed for manual-focus lenses and should not be used on autofocus lenses.

What are some recommended brands of polarizing filters?

I hesitate to recommend a specific filter because new versions of filters enter the market constantly. I suggest you do your research and read lots of reviews that include tests or sample images. I would recommend you buy directly from the manufacturer or an authorized seller like B&H Photo, Adorama, or Best Buy. I do not recommend buying on Amazon. Many photographers have complained of receiving poor quality replicas or knock offs of the products and there are many resellers that are not authorized distributors. Some well-known brands include B+W, Tiffen, Urth, K&F Concept, PolarPro, Hoya, FotodioX (10% off $50), Neewer (15% off), Kase, NiSi, and those made by Canon and Nikon.

The Takeaway…

If you photograph outdoors, particularly landscapes, you will want a circular polarizer. Don’t leave it on the camera all the time, but definitely use it when the circumstances are right and it will improve your photography. Use it to make photos pop – bluer skies, saturated color, and less glare. While you may still have to edit in Photoshop, remember that editing programs – no matter how much “magic” they seem to be able to perform – cannot replicate the effects of a polarizer (when used correctly).

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Curious to know more about polarized light and how to detect it with your own eyes? Check out this article on the superpower you never knew you had: https://theconversation.com/amp/polarised-light-and-the-super-sense-you-didnt-know-you-had-44032