Objects exhibiting polarization (i.e., objects reflecting polarized light) can be made slightly lighter or much darker than other objects not exhibiting polarization simply by turning the polarizer. All good polarizers can be rotated while mounted on the lens. When the polarizer is turned to correspond to the polarization angle of the incoming light (i.e., the angle at which most of the light rays are oriented), the object emitting or reflecting the polarized light is hardly affected. When the polarizer is then rotated 90 degrees, most of the rays of the polarized object are blocked, and it turns quite dark. A second nonpolarized object, however, has the same portion of its light blocked by the polarizer at any angle to which the polarizer is rotated.
Skylight is polarized, as are window and water surface reflections. Lesser-known objects that reflect polarized light include the thick leathery leaves of live oak trees. When the camera is aimed at a landscape that includes sky and clouds, the polarizer can make the sky lighter or darker compared to the clouds because clouds don’t show polarization. The effect of the polarizer can be seen as you look through the lens and slowly turn the filter. You can clearly see the sky grow darker and then lighter as the filter is rotated. The clouds become more or less pronounced as the sky darkens and lightens around them. This is why I used a polarizing filter along with a #12 deep yellow filter when photographing Figure 7-1. The two filters together helped separate the tonalities of the sky from the clouds, but they had little effect on the rest of the image. I’ve employed that combination of filters at other times as well.
When looking at the surface of water, rotating the polarizer can effectively reduce or even eliminate surface reflections at certain angles and allow objects beneath the surface to be seen clearly. You can watch the reflections disappear while subsurface objects become visible as you stand behind the lens rotating the filter. As you continue to rotate the filter, you will reach a point of minimum surface reflection and maximum subsurface visibility. Beyond that point, the relationships will reverse until you reach maximum reflection and minimum subsurface visibility.
The polarizer, like the neutral density filter, can be used in combination with any CC filter or black-and-white filter because it has no color shift. I have often used a polarizer in combination with a red, orange, or yellow filter in black-and-white primarily to accentuate clouds against a blue sky for heightened drama, but for other purposes as well.
Problems Associated with Polarizers
A polarizer has one oddity when used on the sky: it works to maximum effect at 90 degrees to the direction of the sun. When lined up with the sun, it has no polarizing effect whatsoever. Thus, if the sun is directly behind or in front of you, the polarizer is nothing more than a 2-stop neutral density filter. But if the sun is to your left or right by 90 degrees, the sky can be dramatically affected by the polarizer.
There is a hidden danger here. If your photograph includes a portion of the sky 90 degrees to the angle of the sun, and substantial portions of the sky at other angles, the polarizer can make the sky appear very uneven. The portion of the sky at right angles to the sun will be greatly darkened, while other parts will be darkened far less. If the photograph is made with a wide angle lens, the unevenness can be excessive and very distracting.
Another danger is that the polarizer can be misused by rotating it to its maximum polarizing angle. When this angle is used for color slides of dramatic landscapes and cloudscapes, the polarizer can make the sky oppressively blue-black. The viewer becomes more aware of the polarizer than either the scene or the photograph. In a similar fashion, maximum reduction of reflective glare off windows or water surfaces can effectively eliminate the substance of the window or the water itself. In some cases this may be desirable, but in most cases an intermediate angle of rotation allows the reflective surface to be visible as well as the objects behind or under it. With sky and clouds, the optimum angle is often less than the maximum polarizing angle. Overuse of the polarizer is more objectionable in color than in black-and-white because of the closeness of color to reality. Moderation is mandatory for effective use of this tool.
I learned about the seductive effect of the polarizer the hard way. I was photographing a color scene in the rolling, oak-covered grasslands of California near San Luis Obispo in the early 1970s. The leaves on the live oak trees were quite reflective and bright, the grasslands were covered with spring wild-flowers, and the blue sky had streaked white clouds. I used a polarizer to accentuate the contrasts and colors. At the nonpolarizing angle, the filter simply darkened the entire scene. But as I rotated it, the clouds began to pop out from the blue sky and the leaves on the oaks became progressively greener. I finally reached the maximum angle of polarization and was giddy with how colorful everything had become. It turned out that the resulting transparency was a complete dud! By eliminating the reflection off the leaves, I lost all the feeling of light and life—effectively turning the trees into blobs of deep color, as if they were painted. Somewhere between the nonpolarizing angle and the maximum polarizing angle I could have moderately accentuated the clouds against the sky, while at the same time retaining some of the brilliant light off the leaves and moderately enhancing their color saturation. It was a lesson learned.
Note
A polarizer can be misused by rotating it to its maximum polarizing angle. When this angle is used for color slides of dramatic landscapes and cloudscapes, the polarizer can make the sky oppressively blue-black.
It is easy—perhaps compelling—to gravitate toward the maximum polarizing angle because its effect can be intoxicating. Each increment in dramatic effect gains acceptability, making the next one acceptable and desirable as well. Always keep in mind the fact that believability can be pushed somewhat beyond reality—into a realm bordering on “super-reality”, heightened impact, and increased drama—but pushing too far creates a decidedly unreal and obviously contrived photograph.
Chapter 8. The Zone System of Exposure for Film
THE NEXT FOUR CHAPTERS deal with the practical aspects of making a photograph. Chapter 8 through Chapter 10 deal with traditional film exposure and printing. Chapter 8 explains exposure of the film negative or transparency for optimum effect. Chapter 9 explains development of the black-and-white negative for creative, personal interpretative purposes. Chapter 8 and Chapter 9 are so closely tied together that it is difficult to separate them effectively without leaving a temporary gap. The gap is tied together early in Chapter 9, so please read on until the explanation is complete.
(Note: development of color negatives and transparencies is not explored because there is so little leeway in the process. Information about doing your own color processing can be obtained from the manufacturers.)
Chapter 10 discusses methods of printing both black-and-white and color film in the traditional darkroom to express your vision in the most personal manner. Chapter 11 concentrates on the digital workflow from image capture to printing. I recommend that everyone read all four chapters, even if your approach is strictly film or digital, because they provide important insights into how the photographic process unfolds. Such knowledge is never useless.