Keeping It Simple: Circular Polarizers in 5 Minutes
WHAT IS A CIRCULAR POLARIZING FILTER?
A circular polarizing filter (often called a “circular polarizer”) is a filter photographers place on their lens to help reduce unwanted glare (on windows, roads) and unwanted reflections (in bodies of water).
Not seemingly related (but actually related!), another benefit is that polarizers help achieve better color in an image (contributing to bluer skies and greener grass).
WHAT’S REALLY GOING ON (THE SCIENCE BEHIND THE WHOLE THING)?
Light gets “polarized” (sent in scattered directions all over the place) due to the moisture in the air, air particles, pollution, etc. Makes sense, right? Well, this doesn’t make for the best photography; it creates glare and unwanted reflections, and actually pulls away from the color in the scene.
Much of the subject matter we photograph is indeed reflecting light in various directions, creating all sorts of glares, which, in turn, reduces the saturation in our image.
HOW DO THEY WORK?
The circular polarizer only allows for light to travel in one direction into your lens, instead of being reflected all over the place. This one-direction light reduces glare and reflections, and brings back some saturation in your image. Things you may not even consider are reflecting light in all directions - consider a simple leaf on a tree. It can reflect light in all different directions.
WHEN TO USE THEM:
You are at a beautiful waterfall emptying into a beautiful stream, but the sun is harsh and the stream has an ugly shiny glare distracting from the waterfall, and also covering up the beauty of the stream and the rocks underneath the water. Use a polarizer, it will help reduce that glare!
You are shooting an Autumn pond covered in beautiful fallen, colorful leaves, but you’re not seeing the leaves in your image, you’re only seeing a harsh glare on the surface of the water and it’s completely taking away from the color of the leaves. A polarizer will remove the reflection off of the surface of the water so you can see the leaves, and it will even bring out the color of them.
You are shooting a beautiful landscape, yet the sun is fairly harsh and your sky isn’t photographing as blue as you’d like. Use a polarizer, it will not only help deepen the blues of the sky, it will also soften and bring out better colors in the green grass and other colors.
You’re on a product shoot for a cafe, and you want to make an artistic photograph of a client drinking coffee inside of the shop. You want to take the shot from the outside of the cafe looking in, but there is a strong reflection of the outdoors in your window and you can’t even see inside the shop! A polarizer will reduce that reflection and allow your image to capture what was going on inside!
YOU NEED TO KNOW:
Polarizers eat about 1-2 stops of light, so be sure it’s okay for you to lose that light when you’re photographing. If you really need every stop of light you can get, it may not be worth it to use a polarizer.
Polarizers don’t really work when you’re pointing your camera directly into the sun or directly away from the sun.
Polarizers work best when you’re pointing 90 degrees away from sun, so be sure to position yourself correctly!
Don’t assume anything. Always experiment in camera. Take a good look through the viewfinder to see the effect your polarizer is causing to your image that particular day and location. When you’re using a wide-angle lens, sometimes you can see an uneven area of where the filter is taking affect versus where it is not.