This is an A-Z of camera filters for attaching to lenses. If you want to find out more about what camera filters do generally, read this overview article: Filters and when to use them
B
- Big Stopper (Lee filters)
The Big Stopper is a powerful 10-stop neutral density filter from Lee filters. The name has caught on and many now refer to high powered ND filters as 'big stoppers'. The point of an ND filter is that it reduces the light passing through the lens and allows long exposures even in bright daylight. This is the technique used to create blurred water and cloud effects in landscapes.
- Black mist filter
This is a kind of modern-day soft focus filter that takes a different approach. Black mist filters are designed to reduce contrast and soften harsh highlights in portrait shots, and at the same time soften wrinkles, spots and other unwanted facial blemishes.
C
- Contrast filter
A color filter used in black and white photography to change the shade of grey that colors are reproduced as. They're called 'contrast' filters because they can change the contrast (in shades of grey) between different colors.
D
- Drop in (rear) filter
Some lenses have very large or protruding front elements that make it impossible or impractical to use regular filters or filter systems. Instead, they may offer a slot towards the rear of the lens for inserting drop in filters, though the types available and what you can do with them are much more limited that regular filter systems.
F
- Filter factor
This is a calculation used to work out the effect of different filters on the exposure needed, but it's largely fallen out of use with the arrival of digital cameras and especially mirrorless cameras. For example, a red filter, a contrast filter used in black and white photography, might have a filter factor of 3, so that you would measure the exposure without the filter attached, put on the filter and then increase the exposure by 3 stops. to compensate for the filter.
- Filter holder
This is a mounting system for filters which attaches to the front of the camera lens via its filter thread and has slots for inserting two or more filters. Often there will be a slot closest to the camera lens for inserting a dedicated polarizing filter which can be rotated independently of the rest. The other slots accept square filters such as graduated filters or neutral density filters like the Lee Big Stopper.
- Filters
The word 'filters' in photography can have several meanings. Traditionally, a filter is an optical attachment for a lens that modifies the light entering the camera. These come in various types and include traditional round filters that screw directly to the filter thread on the lens, and square filter systems that use a filter holder and square filters that slide into slots in the holder.
- Filter system 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.
- Filter thread
This is a fine screw thread cut into the front of almost all DSLR and mirrorless camera lenses. This is where you screw in round filters, or the adaptor rings for square filter holders. The size of the filter thread varies, so you need to make sure you buy filters or adaptors the right size for your lens.
G
- 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.
I
- Infra red A branch of photography that uses parts of the light spectrum not normally visible to the naked eye but which can still be captured on film or digitally using black and white or colour film made sensitive to infra red or a digital camera modified to remove the infra red filter that normally covers the sensor.
M
- Magnetic filters
Traditionally, filters are attached by screwing them into the filter thread at the front on the lens. This applies both to round filters and to square filter systems, where the filter holder screws on to the lens via an adapter ring. Magnetic filter holders attempt to speed up the whole process using magnets rather than screw threads.
N
- Neutral density (ND) 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.
P
- Polarizing 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.
- Protection filter
This is a clear glass filter that has no optical function at all but is simply designed to protect the front element of the lens from dust, smears, scratches and moisture, even impacts. Protection filters screw directly into the lens's filter thread, so you will need to get one the right size. You can also use UV filters as protection filters, although the UV filtering is hardly relevant today.
R
- Red filter Used in black and white photography to darken blue skies and lighten skintones and foliage. It can produce dramatic, high-contrast images.
- Revoring
This is the name of a filter range created by filter maker H&Y filters. Instead of using a filter thread of a fixed size, it houses a spring-loaded mechanism that can adapt to a wider range of filter sizes, making it possible to use one filter with a different number of lenses. You still have to choose different Revoring sizes to handle small, medium and larger lens sizes.
- Round filters
These are the filters most people think of for camera lenses. They screw directly into the lens filter thread. Common round filters include black and white contrast filters, polarizing filters, soft focus and black mist filters, plus UV filters and plain protection filters for those who like to keep their lenses safe.
S
- Soft focus An effect often used for portrait photography which gives a flattering or glamorous look to female faces. There's more to it than just defocusing the picture, though - soft focus filters add a soft haziness to highlights and areas of even tone but preserve the underlying image detail.
- Square filter
Square filters are designed to be used with filter systems, slotting into a filter holder which attaches to the front of the camera lens. This system of holders, slots and square filters means that filters can be used in combination, and filters that need to be positioned vertically – notably graduated filters – can be moved up and down the slot for precise positioning.
- Step up ring
Step up rings are used to fit a larger filter on to a smaller lens filter thread. They are a useful way to reduce the number of different filter sizes you need to get. They are inexpensive to buy and they are available in just about any combination of lens filter thread and filter size.
U
- 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.
V
- Variable ND filter Variable ND filters are useful in video because here it's often important to maintain the same aperture (iris) setting and shutter speed (or 'shutter angle') to keep a consistent visual effect even in changing lighting – you can adapt to different light levels by adjusting the ND effect.
Y
- Yellow filter
Yellow filters were a popular choice for black and white landscape photography. Like other contrast filters, they pass through the filter color but hold back complementary colours. In landscape photography, that means blue skies are made darker while yellow tones, including most foliage, keep their brightness. A yellow filter is one of the most popular black and white filters, along with the red filter.