One of the easiest ways to substantially improve the image quality of your daytime cityscapes is to use a circular polarizing filter. Putting a polarizing filter on your lens is like wearing a pair of polarized sunglasses over your eyes; the polarized glass blocks random light waves from passing through, creating a clearer image. Randomized light tends to be lower quality than direct light. As such, a polarizing filter will help ensure that only the sharpest, most colorful light hits your image sensor.
1) How Polarizing Filters Work
The vast majority of our planet’s atmosphere is composed of gases that are invisible to the human eye. However, a small portion of the atmosphere is made up of water vapor, pollutants, and other particulate matter. These elements vary in quantity depending on the weather, time of day, and location. Water vapor and pollutants contribute to haze which decreases visibility over long distances, especially in urban centers close to bodies of water. The haze we see is a result of light waves hitting particles in the air, causing randomization. Even on a clear, sunny day the skyline can be obscured by haze. The best way to cut through haze is with a polarizing filter.
Just like atmospheric particles randomize light, so do reflective surfaces. Using a polarizing filter can increase color saturation in your images by reducing reflections from water, glass, leaves, and other non-metal surfaces. Additionally, using a polarizing filter helps you create deep blue skies in your images. Blue light waves are shorter than red and green waves, causing them to scatter more easily. Polarizing your view of the sky will prevent randomized blue light from coming into your lens, leaving you with the purest blue light possible.
Circular polarizing filters have two sections that can rotated to adjust the degree of polarization. Using a polarizing filter is easy; just screw the filter onto the front of your lens and adjust the degree of polarization by rotating the front portion of the filter. Look through your viewfinder as you rotate the filter. The maximum degree of polarization will become apparent as you rotate because the sky will become darker and reflections to be muted. You will get the best results with your camera at a 90-degree angle from the sun’s rays.
Using a polarizing filter is critical when photographing subjects that are one or more miles away. The longer the distance, the more critical it is to polarize the light you are capturing. For example, this image of San Francisco was taken about ten miles away, in the Berkeley Hills. Without a polarizing filter this image would have been soft and hazy. Combining a polarizer with a telephoto lens almost always requires the use of a tripod due to the loss of light imposed by the filter. The stability of the tripod will allow you to use your camera’s base ISO setting and a stopped-down aperture for sharpness while lowering your shutter speed to compensate.
Sometimes it does not make sense to use a polarizing filter. Wide-angle lenses can have an angle of view greater than the effective angle of polarization of the filter, making the sky look unevenly dark in one area and bright in the other. If you want reflections from glass or water in your scene, then do not use a polarizer, either. Finally, polarizers reduce the amount of light that passes through your lens which can hinder hand-held shooting by requiring greater exposure to compensate for the light loss.
3) Closing Words
A good circular polarizing filter is a must-have accessory for any photographer. One of the challenges of being a photographer is making the best of the light you have available to you. Humans do not have the power to control the sun! Polarizers give you the ability to control the light that comes through your lens, creating vibrant images that might otherwise look hazy or dull. Check out this Photography Life article for a deep dive on polarizing filters, or go to this link to purchase the polarizing filter I use for my photographs.