Most of you would have often wondered why we need to use a UV filter whenever we are shooting in Sunlight? To answer that we first need to understand what UV light is and why is it harmful in photography.

For the uninitiated, the visible spectrum of light is made up of 7 colours that stretches from red to violet (see the picture). Red light in the spectrum has the longest wavelength and the violet has shortest. The light which has a wavelength shorter than the violet light is called as Ultra violet light. This UV light is not visible to us from the naked eye and does not have much effect on us either, but it has an effect on the photography film that we use.

A photographic film is called the tripack film; this is because it is made up of 3 layers of primary colours: Red, Blue and Green. The red layer is sensitive to red light, green to green light but blue layer is not only sensitive to violet but Ultra Violet also. Now if UV light also reacts with the blue layer then your image that you obtain on the film will have bluish tinge to it. This is the major reason as to why we use UV filters in photography.

Since digital cameras have sensors instead of Film, they are less sensitive to UV light, but it is still advisable to use UV filters in digital cameras as their sensors can get affected. The Sigma UV 62mm EX DG MC UV filter, for example, has been digitally optimised for use in digital cameras. A UV filter is very easy to use. It just needs to be mounted in front of the lens as most UV filters are available as screw attachments. You can use UV filters can be used for any duration while shooting outdoors as they allow all the visible light to enter the camera, hence do not have any negative effects on your image.