UV filter

Almost colourless filter which is designed to cut blue (UV) haze in distant scenic shots, though this is less of an issue with digital imaging than it was with film. UV filters are still used, though, as a simple and inexpensive lens protector.

Red filter

Used in black and white photography to darken blue skies and lighten skintones and foliage. It can produce dramatic, high-contrast images.

Polarising filter

Polarising filters darken blue skies and can cut through reflections and glare in water, glass and polished surfaces. They come in two types: linear polarisers are cheaper and older and don’t work well with modern autofocus systems; circular polarisers are more expensive but they are the type needed for modern cameras.

Neutral density filter

A filter which reduces the amount of light passing through the lens or reaching the sensor without affecting it in any other way. It allows longer exposures in bright daylight (useful for creative blur effects) or controls bright light in a camera with limited exposure controls.

Graduated filter

Graduated filters are clear at the bottom but darkened at the top, with a smooth, graduated blend in between. You use them in landscape photography to tone down bright skies without affecting the land. You can also create graduated filters ‘digitally’ in image-editing software.

Filter thread/size

This is a fine screw thread cut into the front of almost all DSLR and mirrorless camera lenses. This is where you screw in glass filters, or the adaptor rings for square filter holders. The size of the filter thread varies, so make sure you buy filters or adaptors the right size for your lens.

Filter systems

Most filters these days are designed as modular filter systems consisting of a square filter holder with slots for three rectangular filters and, sometimes, a circular polarising filter too. The filter holder attaches to the camera lens via an adaptor ring. In this way, the same filter holder and filters can be used with many different lenses.

Filters

This can mean the filters you attach to the front of the lens to change the appearance of the picture, or software filters that do the same thing on your computer.

Contrast filter

A colour filter used in black and white photography to change the shade of grey that colours are reproduced as. They’re called ‘contrast’ filters because they can change the contrast (in shades of grey) between different colours.

Black and white filters

It does seem a bit crazy that black and white photographers use coloured filters, but there is a reason for this. When you shoot in black and white, the camera or the film is converting different colours into shades of grey. When you use a coloured filter, you’re shifting and changing the brightness of the different colours in the scene, and this changes their shade of grey in the photograph. This is why they’re sometimes called ‘contrast’ filters too. For example, a red filter allows red light through but blocks light of other colours. Anything red in the scene becomes proportionally much brighter, anything opposite to red, like a blue sky, comes out a much darker shade of grey – nearly black, sometimes.