Analyzing a Polarizer Pitfall

The circular polarizing filter, oftentimes referred to simply as a “polarizer” or “CPL”, is a truly indispensable tool for nature and landscape photographers. Because the light reflected from a given surface is generally all the same wavelength, a polarizer can be used to strategically filter out those reflections. Polarizers are most widely known for their ability to filter out reflected light from the atmosphere, rendering the sky a deep shade of blue when it would otherwise appear very bright and washed-out in an exposure. In my own work, however, I’m generally using polarizers to remove glare from foliage, wet rocks, rivers, waterfalls and ponds. In each of these scenarios, the polarizer can effectively improve contrast, saturation and overall clarity and balance.

But perhaps you’ve heard the advice passed around that polarizers are to be avoided when using especially wide-angle lenses. The warning essentially states that, because lenses with a wide field-of-view can be used to frame a large portion of the landscape, the frame will possibly include multiple areas that reflect light differently. The result? A photograph with patchy polarization, producing strange, unnatural-looking blotches in your exposure. To get a better idea of exactly what can go wrong in such a scenario, I’m going to show you a couple photographs from a recent shoot at White Memorial Conservation Center, a spectacular 4,000-acre preserve in Litchfield, Connecticut.

In this exposure, which is well-balanced, I rotated the polarizer until it wasn’t filtering any reflected light.

Bantam River, White Memorial Conservation Center, Litchfield, CT
© 2012 J. G. Coleman

The exposure to the right is precisely the look I was after in the early hours of the morning at this preserve. Here, the Bantam River can be seen meandering into the distance where it is eventually engulfed in mist at Little Pond on the horizon. As concerns our discussion of circular polarizers, specifically notice how the color and brightness on the river is fairly even. This photograph was taken at a focal length of approximately 18mm, so the field-of-view was relatively wide. Although I did have a polarizer on my lens while taking this shot, I rotated it such that it didn’t filter out any light; you could think of this as the “off position” of a polarizing filter. Because no reflected light was filtered out with the polarizer, you’ll notice that the surface of the Bantam River is seen reflecting the color and light of the sky above.

So, what would have happened if I decided to use the polarizer to block reflected light from the surface of the water instead? On one hand, this doesn’t seem like a bad idea in theory. Hypothetically, I could block the reflection of the sky on the surface of the Bantam River and render the water darker, making it contrast with the surrounding landscape and revealing more detail of the aquatic plant life within.

On the other hand, I would have to be able to filter all of the reflected light from the river for this concept to work. In this case, that’s pretty much impossible. When we examine the scene, a few different problems are noticed. First off, the light in this scene is fairly diffused, resulting from the low light of the pre-dawn hour coupled with the blanket of mist hugging the landscape. This causes light to scatter unpredictably and makes it tougher to filter out reflections, since they aren’t especially uniform. The second problem is the river itself, which stretches deeply into the frame. Nearer portions of the river will reflect light differently than further parts of the river because, from the perspective of your camera, they are oriented differently to the source of light (in this case, sunlight from just below the horizon was reflected by clouds).

In this exposure, I rotated the polarizer so that it was filtering glare from the river’s surface. Notice the distracting and unnatural-looking effect?

Bantam River, White Memorial Conservation Center, Litchfield, CT
© 2012 J. G. Coleman

The bottom-line is that these factors will hamper effective use of the polarizer, essentially making it almost impossible to evenly remove glare from the water. And just in case all of my analysis isn’t enough to convince you, take a look at the photograph to the left. From the exact same position, I spun the circular polarizer until it was removing glare from the river.

Wow… that’s not the effect we were looking for, huh? The large, dark blob in the nearer portion of the river represents the rather small section of the scene from which glare could be removed. It goes without saying that the patchy, unnatural look of the river in this exposure is anything but pleasing to the eye. Instead, it’s exceptionally distracting and disrupts the balance of the entire photograph. In truth, the shot is what I brutally refer to as one of my “throw-aways”. Had I carelessly used the polarizer for my primary series of shots that morning, I would’ve returned home only to be quite disappointed when I reviewed the RAW files on my computer.

Of course, at least one fairly reasonable argument in defense of the polarizer in this scenario might be that I didn’t rotate it to the proper position. Fair enough, I suppose. Indeed, the polarizer will have a different effect depending upon how it is spun in relation to the scene. But, in this case, further rotation of the filter makes little difference due to the same reasons I mentioned earlier. It simply moves the peculiar blob of dark water to a slightly different position on the surface of the river. Take a look at the line-up below where I’ve put the successful shot side-by-side with the previous dud and another failed shot resulting from rotating the polarizer to a different position.

This side-by-side comparison demonstrates the degree to which attempts to reduce glare with a polarizer have ultimately produced rather poor photographs. The keeper shot (above-left) was taken with the polarizer rotated until it wasn’t filtering any reflections, while the filtered shots (above-middle and above-right) show distracting blotches in the river produced by the uneven removal of glare.

Even if the difference between the unfiltered photograph (on the left) and the filtered photographs (middle and right) didn’t seem too drastic when each was viewed by itself, the contrast becomes quite apparent when they are viewed right beside each other. In the improperly filtered photographs, the eye is drawn directly to the dark blotches in the river and the images are rendered rather ineffective as pieces intended to convey the beauty of this misty morning on the Bantam River.

But don’t let this example deter you from using a polarizer. Instead, think of it as an exercise in analyzing a scene before you make shooting decisions. Although the polarizer performed poorly in this scenario on the Bantam River, it can work wonders in other circumstances. The bulk of my landscape work absolutely relies on the benefits of the circular polarizer. Furthermore, I oftentimes use a large 77mm polarizer on my super-wide-angle lens with excellent results, despite the rutted advice that “there’s no need to put a polarizer on a very wide lens”. The only catch is that it’s important to be acutely aware of how the polarizer will modify the light in a given scene and avoid using it in those instances where it will be little more than a hindrance. Admittedly, this may take a bit of practice and will probably involve some measure of trial-and-error before you start to instinctively identify those instances where the polarizer will produce undesirable results. But if you have some spare time during your next shoot, it wouldn’t hurt to produce some of your own comparisons similar to the one I’ve presented here. By experimenting with the polarizer and seeing how it reacts to different conditions and scenes, you’ll sharpen your ability to use this vital tool and make the most of your time in field.

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