How Do Filters Work?
If you are a professional photographer, you must have a set of filters in your camera equipment. Even if you are just an amateur, you probably have one or two filters. What are filters? Why do photographers buy different filters? How do they work?
Camera filters are transparent optical elements that change light properties entering the camera to improve the recorded image. Filters affect the different properties of an image such as sharpness, contrast, color, highlight flare, and light intensity. It can alter one or a combination of these properties, and can also create various special effects.
Camera filters are connected to the front of the lens. Aside from its features, it also protects the lens from elements such as salt air. Some cameras need lens adapters to be able to use filters.
Filters work the same whether you use them on a digital camera or film. There are just a few differences to be considered. Filters that can reduce excess contrast such as polarizers are helpful in a digital camera because digital is more inclined to blow out highlights. Digital cameras are also known to be less sensitive to ultraviolet light, thus, ordinary UV filters may not be needed. Also, infrared filters are easier to use in digital cameras.
Some Filter Types
There are different kinds of filters for a camera and each has its own purpose.
- Ultraviolet filters. As the name implies, this type of filter absorbs ultraviolet light. Cameras, especially ones that use film, have high sensitivity to the invisible light known as ultraviolet light. This is common in making outdoor shots, especially in highly elevated places where there is only a thin layer of atmosphere that absorbs the ultraviolet light.
Without UV filters, viewing far images can be difficult because UV causes a haze that diminishes details with farther distance. UV filters are available in various absorption levels measured by the percentage of transmission at 400 nanometers. A filter that transmits 0% is ideal for long distance and aerial shots. For normal situations, a UV filter with 29% transmission is generally good enough.
- Infra-Red filters. These filters are used to reduce visible light. Filters that can totally absorb visible light and transmit only infrared lights are useful for situations like recording heat effects and aerial haze penetration.
- Natural density (ND) filters. ND filters are used when light intensity is high and proper exposure needs to be attained or when a specific lens opening is required for sharpness purposes. This type of filter evenly absorbs light throughout the visible range which alters the exposure effectively without the need to change lens opening or do color shifts.
- Polarizing filters. Polar filters or polarizers enhance contrast, color and reflection control. It has a different optical principle compared to other filter types. Polarizing filters allows light to pass through in just one vibratory direction. Different alignment can produce different effects to the image. If the filter is aligned perpendicularly to the polarized reflected glare, the result would creat stronger colors because true-colored reflection will pass through.
Polarizers are increasingly being used for outdoor shots to improve contrast and color saturation. A blue sky can be darkened by a polarizing filter, but it has to be blue in the first place.
Polarizers can also minimize and control reflections from water or glass surfaces. To get the best results, an angle of 33 degrees incident to the surface is advisable. The effect can be seen by viewing through while the polarizer is rotated. An object in water can appear as an object out of water without having the reflection.
Optical filters can be a good investment for those who want to make a living out of photography. It allows for different kinds of shots with special effects. It also makes an image look more alive by the different features and effects these filters have to offer.
But even when taking pictures just as a hobby, having some of these filters will be necessary to get the image of clarity desired. Taking a shot without a filter is indeed different from a shot with one.
There are just some considerations that need to be thought about before buying filters. Different types of filters are obviously for different purposes. It is best to determine what the main purpose is and what type of situation is commonly encountered.
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