Subtracts colours, blocking one type and allowing others through, useful for black and white photography.
Reduces light in parts of an image where there are noticeable differences in exposure, useful in high contrast situations.
Blocks visible light, allowing only Infrared light through. For DSLR and Film cameras with Infrared film
(ND Filter) Reduces the amount of light entering the lens and allows the use of slower shutter speeds.
Cuts out reflections from non-metallic surfaces such as water and glass, increases contrast and enhances colour saturation.