The Types and Functions of Optical Filters In Photography
There are several types of optical filters that you can choose from. But all of these filters have only one main function – to transmit light of a certain wavelength or color range and at the same time, prevents the color spectrum from getting through. Basically, there are 2 categories of optical filters. They are the dichroic and absorptive filters. Dichroic filters are responsible in the reflection of the selected wavelengths instead of absorbing them. Consequently, tis filter will transmit the remaining wavelengths. On the other hand, absorptive filters are considered to be made from glass with chosen inorganic or organic compounds added. Such compounds will absorb wavelengths while transmitting other wavelengths. These two categories of filters have several functions. However, dichroic filters get the most of their wavelength ranges can either be reflected or transmitted. In addition to dichroic and absorptive filters, there are also other types of filters. These include the following:
One of the most popular optical filters is the ultraviolet filter. This kind of filter has the ability to effectively block the ultraviolet range of the light spectrum. This filter transmits visible light like an infrared filter. It is usually used in cameras because film is quite sensitive to ultraviolet light. Hence, for an image to be captured on film where human eyes can perceive it, using ultraviolet filter is really necessary.
Just like ultraviolet filters, infrared filters are used to absorb lights so that an image can be captured and eyes can perceive it. This filter transmits light and blocks mid-infrared light spectrum.
Another type of optical filter is the longpass filter. This type of filter is made of colored glass. It transmits longer wavelengths of the color spectrum like visible light, ultraviolet and infrared. This type of filter has also the ability to block shorter wavelengths and frequently serve as emission filters in fluorescence microscopy.
Opposite of the longpass filter is the shortpass filter,. This type of filter transmits short wavelengths instead of long wavelengths. Short pass filters are made of color glass filters and its function is applied to the mentioned wavelength with different effects and results from longpass filter.
If we are going to combine short pass and long pass fil;ters, we will come up with a bandpass filter. These filters do transmit less light compared to both longpass and shortpass filters.
Last but not the least is the polarization filter. This type of filter blocks or transmits light depending on the polarization of the filter. Usually, polarized filters are used in certain camera lenses and sunglasses because it can block some of the spectrum that causes the reflection. As a result, this creates clearer visibility. Moreover, polarization filters have also the ability to darken the bright components in color photography which provide a new approach and appeal to the perceivers.
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