subject: Acquiring Optimum Results From The Optical Filter [print this page] An optical filter is a device that is used for transforming the light from its original state into the desired state. When these filters are used in any device they selectively transmit the light of different wavelengths. These filters are commonly used for photography as well as in many optical instruments and in color change settings in a camera. These filters transmit light through itself and give out special effect. Some special effect filters are commonly used in fashion world photography or normal photography.
The Wikipedia also states that, in astronomy the optical filters are used to restrict light passed to the spectral band of interest, e.g. to study infrared radiation without visible light which would affect film or sensors and overwhelm the desired infrared.
Photographic filters do not need the accurately controlled optical properties and precisely defined transmission curves of filters designed for scientific work. But some special filters, used for specific purposes need special treatment or special precautions for making of these filters. optical glass filters are very common example of a barrier of light which transforms the light into a special effect. These filters are commonly made from glass to which various organic or non- organic compounds are added. Modern technology also has achieved this feat by adding these compounds to the plastic in order to achieve the similar effect. So, there are some glass based filters, which are little heavier and expensive, whereas there are some plastic based which are lighter and more inexpensive. These filters are available in various colors for better color effect. The range varies from natural white to tan dark. They are called colored or neutral density filters, depending on their color or density or shade.
Following are some types of optical filter glass: absorptive filters, Dichoric filters, monochromatic, infrared and ultraviolet, neutral density, long pass, short pass, band pass, guided mode resonance, metal mash, polarizer etc . These filters can be classified and defined using their names itself. The first one has absorbing quality, whereas the second one is also referred as reflective, interference or thin film. Monochromatic filters allow a very narrow range of wavelengths to pass through. The infrared can either block the infrared rays or allow only infrared rays to pass through, same explanation is applied in the case of ultraviolet filters. Polarizer is normally used for making sunglasses as these filters block reflected light.
