Photography Filters

There are three main types of photography camera filters. They are glass like circles or squares placed in a mount that screws into the filter thread of a lens. They can used in conjunction with almost all inter changeable camera lenses to add creative effects to an image or to correct the predictive colour cast of a light source. Filters can be categorized by their purpose into the the following groups. 

Colourless photography filters

Skylight And UV Filters

Skylight and UV filters are often used to protect the front of a lens, the logic being that any damage  caused to a filter is preferable to any damage being caused to the front of a lens. 
Similar to UV filters a skylight filter will filter ultaviolet rays reducing flare and UV haze although skylight filters are slightly pink in colour to compensate for the blue casts sometimes present when shooting landscapes and other outdoor scenes.

Polarizing Filters

A polarizing lense will reduce flare and glare from reflective surfaces such as glass or water. They can also transform ordinary colour into strong colour under certain conditions and darken blue skies without affecting other colors.

Neutral Density Filters

Neutral density filters can reduce the amount of light entering a lens. This can be helpful under bright conditions when a large aperture is required to reduce depth of field for a deliberately out of focus foreground.

Special effects photography filters

Close Up Filters

Cloes up filters are available in four different strengths, +1, +2, +3 and +4. They allow closer focusing than the camera lens would normally allow. very useful for those extra close up macro shots. 

Soft Focus, Soft Spot, Colour Burst, Rainbow Focus & Star Burst

All of these type of filters do as their names would suggest. Their uses though are all quite limited and cliched in their effects,

Graduated Filters

Graduated filters comprise of only one colour that fades to transparent. Mostly used in landscape photography they can change the colour of the sky to any colour you want while leaving the landscape below the horizon untouched in the transparent part of the filter. A particularly good filter for landscapes is the neytral density graduated filter. This will not change the colour of the sky but will reduce the brightness of it to something nearer to the correct exposure required for the land. 

Split Field Filters

These type of filters allow you to focus very close to a subject and retain the same clarity for the background. This is achieved by placing a diopter, or close-up lens,  in one half of the lens frame. The other half has no lens at all so you can focus on the background object as normal while the diopter focuses on the close-up subject.

Contrast Control Photogeaphy Filters

These are mainly used with black and white film cameras to affect tonal values. They lighten their own colour and darken their complementary colour. 
  • Yellow, is used to subtly lighten orange and red tones while darkening blue and purple tones.
  • Orange, is used to increase sky contrast, reduce haze and subtly darken foliage.
  • Red, is used to dramatically increase sky contrast and darken green tones.