Camera lens filters still have many uses in digital photography, and should be an important part of any photographer's camera bag. These can include polarizing filters to reduce glare and improve saturation, or simple UV/haze filters to provide extra protection for the front of your lens. This tutorial aims to familiarize one with these and other filter options that cannot be reproduced using digital editing techniques. Common problems/disadvantages and filter sizes are discussed towards the end.
Linear vs. Circular Polarizing Filters: The circular polarizing variety is designed so that the camera's metering and autofocus systems can still function. Linear polarizers are much less expensive, but cannot be used with cameras that have through-the-lens (TTL) metering and autofocus e— meaning nearly all digital SLR cameras. One could of course forego metering and autofocus, but that is rarely desirable.
Filters may also introduce physical vignetting (light fall-off or blackening at the edges of the image) if their opaque edge gets in the way of light entering the lens (right example). This was created by stacking a polarizing filter on top of a UV filter while also using a wide angle lens r— causing the edges of the outermost filter to get in the way of the image. Stacking filters therefore has the potential to make all of the above problems much worse.
Light travels in waves. When light strikes an object it is modified by the object. Light is absorbed by dark objects and reflected by objects like water, glass or rocks. To eliminate unwanted reflections in specular highlights, photographers use a filter on their camera lenses called a polarizing filter. This filter will allow you to control unwanted reflections from glass or water in your photographs. It can also be used to deepen the color of the sky or increase the differences between a cloud and the sky. It will remove glare from most views, but will have little impact on metal objects, which reflect mostly non-polarized light. The following are ways to use a polarizing filter with your camera lens.
