A circular polarising filter works by changing the beams of polarised light that enter your camera’s lens when you’re taking a photograph. Polarised light enters the lens directly in certain situations, creating glare or reducing the natural color in a picture. When a circular polariser is on your lens, you can rotate it back and forth to block the direct beams of polarised light, giving you a better photograph in outdoor lighting shots.
How to use one in the field
1. Choose a circular polariser by looking at the size of your lens. Lenses run in common sizes, such as 55mm or 52mm, and this number will be on your lens. You will need to obtain the same size when buying the filter.
2. Attach the circular polarising filter to your lens and head outside on a sunny day. The best way to learn how to use the filter is to experiment with it. Reflections on water and clouds against a blue sky make two good learning situations.
3. Point your camera towards a reflection in the water and look through the viewfinder. With the hand that you do not use to depress the shutter, slowly turn your circular polariser 90 degrees. Notice if portions of the shot darken slightly. If there is a lot of bright sun, it may be difficult to witness the change in the viewfinder, so take one shot each of each position to study later when you are indoors.
4. Change your position in relation to the reflection. This is often the most confusing aspect for a new user of a circular polariser. When you understand that the polarized beams of light are reflecting in a specific direction, due to the angle of the sun, you will begin to see that knowing where to stand to get the shot is the key.
5. Try an easy trick when learning where to stand in relation to the sun’s rays. Hold your hand as if you’re making a pretend gun, with your index finger pointed at the reflection and your thumb held upward at a 45-degree angle from your finger.Walk around until you can rotate your hand, while keeping the same finger alignment, so your thumb points at the sun while your index finger is still pointing at the reflection. From this position, rotate your hand from one side to the other, still pointing at the reflection. The place your thumb points to on either side is optimal for standing when photographing the reflection.
6. Take more practice shots of the reflection from the designated spots and view them indoors to see the difference. Use that technique anytime the sun is shining and you want to reduce reflections with your circular polariser.
7. Remember they also can get you to see through the water depending on how far you rotate it