Using a Polarizing Filter

This installment of Tips and Tricks is a little bit early, and actually is a special entry. It has been prompted by Julie from My Photo Journey. In the linked entry, she talks about using her new polarizing filter which is probably the absolute, single best filter to have for landscape photography. We talked a bit about the filter and the uses of it. Unlike the majority of camera filters out there, the polarizer takes a little bit of understanding before you really reap the benefits.

With the fall leaves just around the corner, everybody will be wanting to head out and capture the beauty. I would recommend a polarizing filter for these shots for several reasons. First, is that incredible blue sky you can get. Second, this filter actually removes surface glare from leaves, water, and any non-metallic surface. It is a workhorse filter, but has some caveats and limitations. Here is the quick and dirty of how to use a polarizing filter.

Straight out of the box, the filter looks like any other with the exception of being able to rotate while attached to the lens of a camera. It is a dark glass that looks similar to a lens from a pair of sunglasses (see picture below). How will this dark glass brighten colors, remove glare, and darken the sky? Well, what it does is filter the polarized, reflected light in the atmosphere which is the type of light that leads to glare from water molecules, both in the air and on surfaces. The end result is more color saturation, and better contrast without the glare.

There are two types of polarizing filters, a circular and linear. In the early days of auto focus cameras, a linear polarizer would cause problems with the auto focus. To combat that, a circular polarizer was created. Outwardly, there is no difference, but the way the light is filtered is changed as to not affect the auto focus. In today's cameras, both types will usually work, but to be on the safe side, try to choose a circular polarizer (CPL). You will notbe able to tell any difference in your pictures between the two.

Installing the filter is easy enough, just screw it on the end of the camera lens. Of course, you will need a lens that is threaded for filters. Also, be mindful of the diameter of your lens so you get the right size. With most filters, you are all set and ready to take pictures. Not so with the polarizing filter. As you can see in the picture below, once installed there is very little difference in the appearance of the camera or its function. However, you now have an additional avenue of control over your picture.

You will notice that a polarizer has two different rings with the glass being mounted on the outside ring. The inside ring is threaded to mount to your lens. This is not just a ploy to raise the price, costing you more for no reason. This is where the magic happens. Once fitted to the lens, the outer ring, containing the filter element, can be rotated (See picture below). This is to allow you to filter the directional, polarized light source. It is not an on/off affair either. You can decide how much or how little effect you would like in your picture.

This is just the beginning. To gain the full effect from the filter, you must also know some other aspects of its use. To get that blue sky the polarizer is known for, there are some simple rules you must follow. The maximum effect of this filter can be seen when used ninety degrees from the sun. DO WHAT?????? OK, this is not as difficult as it sounds. Make an "L" with your thumb and index finger, like a gun. Point your index finger to the sun, paying attention to where your thumb is pointing. Now, keeping your index finger to the sun, and arc your thumb around from left to right. The areas your thumb points are the areas of maximum polarization. Try to stay near those locations.

The closer you get directly to the sun, or directly away from the sun, the less of an effect you will see in the final picture. Also, the higher in the sky the sun is, the less effect you will get. At noon, you will hardly see any effect regardless of which direction you are shooting.

If the sky is not your concern, and you are wanting to remove surface glare from foliage, or water, then direction, nor time, is that big of a concern. In fact, when I am working on intimate landscapes that exclude the sky (ie: waterfalls, macros, and streams), I still use a polarizer to saturate my colors, and keep glare down.

OK, now that we are clear on what situations we can use the filter, we can move on to how to use the filter. Remember that the outer ring adjusts the effect of the filter. For those with full auto cameras, it might be difficult to see the effect in the view finder. You might need to lock the exposure (hold down the shutter button half way) and rotate the filter until you see the effect you like. Release the shutter button, recompose, and take the shot. Those that are more manually oriented, will see the effect in the view finder with no problem. Keep in mind that the filter will cause under exposure by up to two full stops, so after you set the effect, you will need to adjust your exposure. The nice thing, is, once you set the filter you can leave it until you change orientation (vertical or horizontal), or drastically change your shooting direction or position.

The polarizer is not really a magical device, it will not create blue where there is none. The best time to use it when including the sky in your pictures, is on days the sky actually looks blue. The more existing blue in the sky, the better the effect will be. If there is a lot of haze in the sky, or lots of clouds, then you will capture images with a white sky regardless of a polarizer.

The downfall to a polarizer is the exposure effect. Slowing the camera down up to two stops can make the difference between being able to hand hold and having to mount the camera on a tripod. If you customarily handhold the camera, this could pose a problem. It can be overcome by raising the ISO with the tradeoff of more grain, or digital noise in the image. You could also open up the aperture allowing more light to enter the lens. However, you reduce depth of field this way. For me, these are not concerns as I normally mount the camera to atripod for my shots. Shooting at ISO64, and stopped down for maximum depth of field, it is not uncommon for my shutter speeds to be in the neighborhood of 3/4 second in broad daylight. There is no way to handhold at this speed.

An example of the use of the polarizer to deepen the blue of the sky.

An example of how the polarizer will deepen the blue and make the clouds stand out against it.

These filters are not cheap and will range from $30.00 to well over $200.00. Don't scrimp here, get a good multi-coated (to avoid ghosting and flare) filter from a reputable manufacturer. I personally use a Hoya Pro-1D Circular Polarizer from The Filter Connection. I also carry a Cokin backup just in case.

Written by Greg A. Kiser