Benefits of Polarizing Filters
The main goals of using polarizing filters are to delete "soft" reflection, reduce white-outs and glare from nonmetallic surfaces, and in most cases increase the color balance. For example, whitish sky might become rich-blue on a photo where the filter has been used. This along with great composition can totally change the viewers' impression. In short, a polarizing filter is definitely a "must have" accessory for every professional photographer and may be used for both black-white and color photography.
Types of polarizing filters
Although armed with such good intentions, buying a polarizing filter may lead to confusion. There are a lot of different types, and you may encounter up to 7, including: C-PL, MC-CPL, Wide C-PL, Water Proof Coat C-PL, DHG C-PL. How do they differ?
The first filter, called PL, is used with MF (manual focus) cameras only, and it uses a linear polarization. The second type is for all type MF / AF (manual / automatic focus) cameras and uses a circular polarization. If you are using polarizing filters with an auto focus camera, ensure that the filter has the С.PL / C-PL logos on it, or it is otherwise clearly marked as a circular polarizing filter. We will discuss below why that is so important. Some filters with larger diameters are linear only. Filters with MC – CPL and MC – PL marks use multilevel coating, effectively minimizing glare and reflections and providing more light. Water Proof Coat C-PL or WPC-PL, as it stands from the name, has a water resistant material on the external surface. The last one, DHG C-PL-filter is specifically designed to protect a digital cameras lens.
The light polarized by a linear filter (PL) can cause errors of aperture and focus measurement in all auto focus digital cameras. With polarizing glass turned equal to 90 degrees, the digital camera most likely will stop processing the picture at all. To avoid this, it is recommended to use circular polarizing filters (C-PL) that will not cause such effects. There are no other differences between these two major types of filters, so you can select the one most appropriate to your purpose.
How to use polarizing filters?
With a manual focus camera, it is simple: 1) install the filter onto your lens, 2) start rotating the filter checking the result through the view finder. The most noticeable effect is in the dark parts of the composition. Use the ^ mark on the filter for more accurate settings. Sometimes you may find that the effect is minimal due to the location of the light source (usually the sun). If light falls to a surface under 90 degrees on the side closest to the axis of the lens, the effect of polarization may not occur. At the same time, if the sun is about 90 degrees on the side closest to the axis of the lens, the effect will be maximal. In order to reduce glare on surfaces like water, the lens has to be about 30-40 degrees from the surface level.
You can also use polarizing filters with other types of filters. When doing so, the polarizing filter should be the last filter on your lens. This rule is not hard to remember because in most cases polarizing filters have no external threading. Try it! The combination of color and polarizing filters may give unusual effects, extending or reducing some of the colors in the photo.
One last point to keep in mind: since polarization filters use iodine, they can not resist heat and ultraviolet light. Therefore, apply the filter only when you really need it and keep it in a case the rest of the time. Simple! Used properly, a polarizing filter will last for about 5-6 years before it needs replacing.