When applied correctly, a filter can become an integral part of the imaging process. Filters use light to enhance and contrast colours to create a specific mood to the image you are shooting. There are a broad range of filters that can be applied - from colour grads, effects and corrections, to neutral density and black and white filtration.
Colour Effect Filters
Colour filters allow you to provide exactly the desired level of colour effect, and are primarily used to add colour to part of a scene where colour may be weak or absent. They enhance reality and can be used to affect elements such as skin tones, sky and foliage. For a softer shade, graduated colour filters are part-clear and part-colour and either transition with a soft edge for gentle merges, or a hard edge for an abrupt change. These are used in uneven lighting situations to balance exposure. Alternatively, day-for-night filters are the perfect way to create a night time or dusking feel when shooting during the day.
Neutral Density Filters
The primary purpose of using neutral density filters is to regulate the amount of light that can pass through the lens. All neutral density filters are grey in colour, and the deeper the colour the more effective the light reduction, whereas graduated neutral density filters brings an overly-bright part of the screen into the dynamic range of film. It is made up of a half-neutral and half-clear density and transitions with either a soft or hard edge. A good example of where to use a graduated neutral density would be where you need to darken a bright sky to allow both the sky and subject to be properly exposed.
Outdoor & Indoor Filters
For use when the sun is too bright and the shadows too dark and it is difficult to get good detail in both at the same time, low contrast filters reduce contrast by allowing more shadow detail visibility, ideal for those who shoot video and desire a film look.
To deal with refracting light, polarisers are ideal when photographing into water or through glass as they are used to eliminate surface reflections, glare or hotspots from any external light sources. They also darken blue skies and increase colour saturation.
Supermist filters are the ultimate tool for softening images to create a mood indoors or outdoors, in broad scenic or portraits. They moderately lighten shadow areas without detracting from the overall image, which allows you to tone down any excessive sharpness.
UV, Skylight and Haze Models
Because CCD's are vulnerable to Ultra Violet rays, if UV light is recorded on the CCD, it is possible that your image will have a blue taint and the colour casts may not be acceptable. These filters can also eliminate a lack of sharpness created by UV radiation and reduces distant haze. UV filters are clear, whereas skylight filters come in a pink shade, which produces a warm glow.