Camera Filters: How They Work
By: Ted Burns

The purpose of filters in a camera is fundamentally the same as filters in other tools: trapping dirt or large, undesirable particles. Camera filters, though, help to produce many desirable effects and enhanced looks in photographs.

Professional photographers usually have more than one filter packed together with their large lenses. Even for amateurs, it is helpful to have a few different filters on hand.

To be effective, a camera filter must be aligned with the lens. A transparent optical element is designed to modify the light that comes through the lens when the shutter opens. As a result, we see improved quality in pictures. Moreover, a filter can also protect the lens, particularly from salt air that with too much exposure would destroy it.

Both film and digital cameras use the same kind of filter; though digital have some other considerations. For example, digital cameras have a greater tendency to blow out highlights. As such, polarizers may be helpful to lessen contrast. Additionally, ordinary UV filters are no longer needed because digital cameras are ultraviolet light sensitive. And infrared filters are also easier to use.

Some Filter Types
There are many types of camera filters, each with their own set of purposes.

1. Ultraviolet (UV) filters absorb ultraviolet light. Ultraviolet is invisible light, and film cameras are more sensitive to it than digital cameras. At elevated locations, ultraviolet light is particularly dense; this density is due to the thin atmospheric layer.

UV light produces haze that can cause photo details to regress as the subject moves farther away. The viewing and focusing of images can also be difficult.

2. Infrared filters reduce visible light. When capturing aerial haze penetration and heat effects, infrared filters are helpful. This kind of filter absorbs visible light and transmits only the infrared light to the lens of the camera.

3. Natural density (ND) filters can be used to obtain proper exposure in high intensity lighted surroundings. It is also used to produce a specific opening of the lens for image sharpness and absorbs light evenly from the visible range. In effect, ND filters alter light exposure, even without changing the lens opening.


4. Polarized filters enhance contrast, reflection, and color control. Compared to other filters, they are built on different optical principles. In just one vibratory direction, a polarized filter allows light to pass through. This kind of filter can be aligned in many ways, giving the image more interesting effects.

Polarized filters are normally used for taking pictures outdoors because they enhance color saturation and contrast. They also create different colors. For example, a yellow bright light can be produced using a yellow polar filter.

Reflections from glass or water surfaces can also be controlled, or at least minimized, by polarizers. The recommended angle is 33 degrees from the surface to obtain an impressive result. This filter can make an object in the water appear to be outside of it simply by rotating the lens.

5. Optical filters allow different shots with different special effects. These filters can make a subject appear more alive.

Whether taking pictures is a hobby or a profession, filters are an important part of the photography arsenal to achieve impressive results. Filters can produce a very noticeable difference in pictures compared against those without any filtering.

About the Author
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