How to Use a Circular Polarizer Filter

Add drama to your photographs with this essential filter

Photographer taking a landscape under snowy mountains

Robert Postma / Getty Images

While many old-school film filters are now obsolete in the world of digital photography, a few remain very useful. One of these is the circular polarizer filter.

The circular polarizer can be used to add dramatic effects to your photographs and it is one of the tricks that professional photographers rely on to create brilliant images with rich colors and dynamic contrast. However, you need to know how to use it to get the best out of it!

What Does a Polarizer Do?

Put simply, a polarizer reduces the amount of reflected light that goes to your camera's image sensor. It is a way to cut out the junk light and haze of the atmosphere and allows the camera to capture a clearer, crisper photograph.

If you have worn polarizing sunglasses on a sunny day at the lake, then you have seen what polarizers can do. With a polarizing lens, blue skies appear a deeper blue and the clouds seem to pop out from the background. Any reflections of the water are removed and you can see deeper than you can without your glasses. The polarizing filter can have the same effect on a camera.

How to Use a Polarizing Filter

Polarization is most effective at 90 degrees to the sun (or light source). Maximum polarization will occur when your subject is at a right angle to the sun. At 180 degrees (when the sun is behind you) polarization will be non-existent. Between these two points, the amount of polarization will vary.

A circular polarizing filter screws onto the front of the camera lens and has two rings that rotate. To use a polarizer, simply twist the front ring to activate polarization.

Look inside the camera while turning the filter ring. You will know that you have achieved polarization because reflections will disappear and the contrast between a blue sky and clouds will increase.

Practice with reflections and blue skies while getting used to the polarizing filter. Take some photographs of the same scene at maximum polarization and without polarization and compare the two. The difference should be dramatic.

Once you become aware of the effects of polarization you will find its usefulness even when there is not a sky or reflection in the image. These are just the two best examples used to explain the effects of polarization. Many professional photographers rarely take a polarizer off of their lenses, that is how valuable this filter is.

The Drawbacks of a Polarizing Filter

Bear in mind that using a polarizing filter will reduce the amount of light reaching the camera's sensor by as much as two or three f-stops, so you will need to adjust for this. Choose a slower shutter speed (and use a tripod if needed), open up by choosing to a lower f/stop, or add more light to the scene (at the same angle, if possible).

Low light conditions are not ideal for using a polarizing filter. If you need to cut a reflection late in the day or want to maximize the clouds at sunset, use a tripod.

It is best to set your focus then find the point of maximum polarization. This is because the front ring of the lens that the polarizer is attached to can rotate while it focuses and throw off the polarization. Even if you have to refocus after polarizing, the filter should still be in the general alignment that you left it (unless you change focus points).

Buying a Polarizing Filter

Polarizing filters are not cheap and it is important to keep quality in mind when shopping for one. Remember that the sharpest photographs are produced by a good, quality glass and the same attention you put into the optical quality of your lens should go into your polarizing filter.

Do not purchase a linear polarizer to use with a DSLR. These are used for manual focus film cameras and, while they can polarize light more dramatically than a circular polarizer, they can damage your camera's electronics.

Circular polarizers were developed when film cameras began to use autofocus lenses and complex electronics because linear polarizers did not work with the new technology. If a filter says only says 'polarizer' on it, then it is a linear polarizer. Circular polarizers will always say 'circular polarizer.' This is very important to look for when searching through bargain bins of camera accessories!

If you have multiple lenses with different filter sizes you may be able to get away with a single polarizing filter. As long as the difference of the filter sizes is not too drastic, purchase a step-up or step-down ring. These inexpensive adapters come in various sizes and can be used to fit, for example, a 58mm filter onto a lens that takes 52mm filters.