Using Polarizers
Left Image: 35mm SLR, 50mm f-2.8 macro lens, Kodachrome 25, Polarizing filter to make the red stronger, Bogen tripod and ball head. Centerweighted metering, exposure not recorded.
Polarizing filters are a must have accessory. These filters can be used to darken blue sky, remove reflections off shiny surfaces, saturate colors, or be used as neutral-density filters. By rotating the filter, you can block the polarized components of light without affecting normal light to pass through. You loose one to two stops of light when using polarizers depending on how much you rotate the filter. When you want to darken the blue sky, the maximum effect is achieved at right angles (90 degrees) to the direction of the sun. A quick way to determine the maximum polarization is by pointing your index finger at the sun and extending your thumb at a 90 degree angle. This is like pointing a gun. Rotate your wrist from side to side while still pointing your index finger at the sun. The greatest effect will be at 90 degrees where your thumb is pointing at. Polarizers also remove reflections from shiny surfaces and saturate colors. This is where I use polarizers the most. By adding a polarizing filter, you can bring out color in your subject. In sun light, you can remove haze, and in overcast days or in the rain remove reflections from your subject to get more saturated colors. The best way to decide when to use a polarizer is by looking through and rotating the filter before attaching it to your lens. If you like the effect you see, attach your polarizer. Your camera meter will automatically compensate for the loss of light, but if you are using an incident meter or a camera without a built-in meter such as non-TTL prism finders on medium format cameras, you must open up between 1 to 2 stops. At minimum polarization, you loose 1 stop of light, and 2 stops at maximum polarization. There are two types of polarizing filters, circular and linear. Autofocus cameras need a circular polarizer to meter and autofocus correctly. Manual focus cameras can use either type. If you have a linear polarizer that you want to use with your AF camera, meter and focus on your subject first and then attach your polarizer. You need to make manual exposure adjustments depending on the filter factor to get proper exposure. Polarizers used with wide-angle lenses can cause Vigenetting. Avoid thick filters if you are buying a new polarizers. The newer wide-angle filters solve Vigenetting problems by having a wider glass.