How to Use a Circular Polarizer in Landscape Photography
Circular Polarizing filters are indispensable since they enable photographers to achieve creative, in-camera effects across many different scenes. Whether shooting deserts, oceans, forests, lakes, mountains, or jungles, a landscape photographer will find a reason to use a Circular Polarizer (CPL or CP). Second, the CPL effect needs to be captured in the camera on location. It is incredibly difficult, if not impossible, to reproduce the effects of the CPL in post-production.
A Circular Polarizer works by removing scattered light and only allowing light rays which are traveling in one direction to enter the lens. By filtering out scattered light, a CPL is able to remove glare from water, glass, or wet non-metallic surfaces. For example, it can reduce glare from wet surfaces like rocks and leaves in a water scene. In doing so, it enriches the colors and increases the contrast.
Additionally, a CP filter can block one to two stops of light from entering your camera. For water scenes, slowing down your shutter speed produces a small softening effect on moving water. Furthermore, it can cut through the haze in the atmosphere enriching the colors of the scene and increasing the contrast, such as deepening the blue in the sky.
Since the filter works by turning it on your lens until polarization is achieved, the majority of Circular Polarizers are screw-in or round in shape. The effect is strongest when facing 90 degrees to the sun. Therefore, depending on the scene as well as the location of the sun, it is possible to have no polarization occur when turning the filter. This is why it is important to know how and when to use the circular polarizer.
Last, there are a couple items to keep in mind when using a Circular Polarizing filter with very wide lenses. With wide-angle lenses, a CPL may cause some vignetting in the corners of the image. Similarly, it can deepen the blue in the sky unevenly where it appears surreal. Since wide angle lenses capture a large area, the center of the image is where polarization is the strongest. The sky will be the darkest there. Whereas, the edges are less polarized and lighter. Therefore, it is important to adjust the filter for the desired effect on the image.
The Visual Wilderness articles offer guidance on using a Circular Polarizer in various scenarios as well as offer advice on how to approach vignetting or working with uneven polarization.