Lens Filters Explained
Along with a variety of lenses, spare batteries and lens cleaning cloths, most photographers will also have a selection of filters in their camera bag.
But what do lens filters do? What lens filters are essential? And what is the difference between circular and linear polarisers? I answer all of these questions and also address when and why you might need filters and how they can help you get more creative with your photography.
What do camera lens filters do
There are several different types of lens filters and each one does something different. Some filters help to remove reflections, while others enhance particular colours in an image or limit the amount of light that passes through the lens.
Essentially though, filters are pieces of glass, plastic or resin that fit over the front of your camera lens to help you further control the light to reach the desired result.
Types of lens filters
There are many different types of filters available, so I’ve put together a list of the ones I commonly use and explain a little about what each one does. These are also explained in the video, along with some examples of where I typically use them.
(Linear vs circular polarisers)
One of the most commonly used camera filters, polarising filters (or polarisers) help to cut out reflected light in an image, increase contrast and enhance saturation.
The amount of polarisation achieved can be adjusted or controlled by rotating the filter.
There are two types of polarisers: linear and circular polarisers. Both types result in similar amounts of polarisation, but the way they cut out certain light frequencies differs.
The most important difference between linear and circular polarisers is that circular polarising filters allow the camera's metering and autofocus systems to still function. Linear polarisers, although significantly cheaper, tend to interfere with the auto-focus system on modern DSLRs and are better suited if you’re working in manual focus and setting the exposure yourself.
Polarising filters are commonly used for landscape photography, particularly where you want to remove reflections on water or enhance contrast in the sky, but I also use them in the studio, where they are particularly useful for controlling reflections on items with gloss surfaces (such as cars).
Neutral density filter
Neutral density filters (commonly referred to as ND filters) work similarly to sunglasses. These filters are darkened pieces of glass that reduce the amount of light that is able to pass through the lens and therefore allow you to use slow shutter speeds in scenarios where you otherwise would have been limited by the aperture and ISO.
Generally, filters that reduce the light by just a few stops should be adequate, but filters like the LEE Filters Big Stopper, which reduce the light by 10-stops, can be useful if you’re photographing in broad daylight or require long exposures of several minutes.
These can also be used if you want to achieve creative effects in landscape photography or ‘remove’ people from images (the reduction in light should allow you to use sufficiently slow shutter speeds that the movement of the people will essentially ‘erase’ them from the image).
It is worth noting that some neutral density filters can cause unnatural colour cast in images, which can be problematic if you’re using them in the studio. However, depending on the severity of the discolouration, this is something you can generally fix in post-production.
Graduated neutral density filter
While neutral density filters are uniformly-tinted pieces of glass, graduated neutral density filters are filters that are clear on one half and tinted on the other half.
These filters are particularly useful for landscape photography or situations where there is a noticeable difference in exposure between two parts of the image (such as the sky ad the foreground).
Graduated filters are available in a variety of options. Not only are they available in different strengths, but you can also get ‘hard’ or ‘soft’ graduated filters (this refers to how quickly the filter transitions from clear to dark).
Depending on what filter system you use, you can combine these with ND filters if you need greater reductions in light.
I’ve used graduated ND filters for more than just landscape photography, I’ve also used them for fashion photography, as you’ll see in my ‘Photographing fashion on the coast with flash lighting’ class.
If you don’t have graduated ND filters, it is possible to move ND filters around in front of the lens to create a similar effect, as I show in the video below.
Also referred to as clear or haze filters, UV filters are another commonly used type of filter that are designed to cut out UV light (the bluer light you commonly see in shadows).
The usefulness of these filters is debatable, with some photographers arguing that these filters increase flare and decrease contrast and others claiming they help reduce chromatic aberration and offer a convenient way to protect the front of the lens.
Personally, I find their impact negligible and prefer not to shoot through more glass than is necessary.
More commonly used with film cameras, colour filters can still be useful for black and white photography.
When shooting black and white, the colour of the filter being used blocks certain colours from reaching the sensor and therefore changes the appearance of other tones in the image.
One of my favourites is a red filter, which is particularly useful for black and white landscape photography. This particular filter cuts out cyan or blue light (the opposite to red), which helps to create dark, dramatic skies with bright white clouds.
Lens filter sizes & systems
Depending on the brand of filter, filters are available in different shapes, sizes and materials and attach to the camera lens in different ways.
The system I use, LEE Filters, attaches using a drop-in filter system, while others, such as some of the Tiffen and Formatt-Hitech filters, are available as circular screw-on filters. Other filter systems include rectangular filters and square filters.
Each system has their pros and cons, though I prefer the drop-in system as it allows you to easily stack multiple filters together (for example an ND filter with a graduated filter) and it means that instead of buying multiple-size filters for different lenses, you only need to buy the relevant adapter ring.
The adapter ring allows you to attach the filter holder to the lens; these are available in different sizes depending on the lens you’re using.
For example, the Canon EF 50mm f/1.2L USM lens has a thread size of 72mm, while the Nikon 18-55mm f/3.5-5.6G VR has a thread size of 52mm.
To know what size filter or adapter ring to use for any lens, you can either check the front of the lens itself (the size is usually indicated by a number with the symbol Ø, which shows the size in millimetres), under the lens cap, or it should be listed as part of the specs for that particular lens.
When to use filters
It goes without saying that you don’t always need filters, but they can certainly be a useful tool to have in your arsenal.
I tend to use filters when I need to further control light, whether that be in the studio or out on location, and the filter I use depends on what I want to achieve. Below is a quick summary of the filters discussed and when to use them.
Polariser Filter (Circular/Linear)
Control/remove reflections; increase saturation/contrast
Neutral Density (ND) Filter
Reduce light and allow for slower shutter speeds or larger apertures
Graduated ND Filter
Reduce light in parts of an image where there are noticeable differences in exposure
Cut out UV light; protect the lens
Cut out/introduce certain colour light; enhance contrast for B&W photography
What lens filters are essential
Even as a product photographer, filters are a key piece of equipment in my studio and something I use for both studio photography and shooting on location.
Most commonly, I use ND filters, ND graduated filters and polarising filters, but what I use depends on what I’m photographing.
For landscape photography, most of the filters I’ve discussed here can be useful, particularly polarisers, ND filters and ND graduated filters.
Landscape image without graduated ND filter
Landscape image with graduated ND filter
For portrait photography, filters are less commonly used. However, they can be useful if you’re shooting on location, in which case having a few ND and ND graduated filters may be useful.
For product photography, I tend to most commonly use polarising filters, though ND filters can also be useful if I need to cut out additional light (for example if I need to shoot with a larger aperture and can't reduce the power of my lights any further).
Further information about each of the filter types discussed here can be found in the following classes:
For more practical examples of how to use lens filters for photography, take a look at the selection of classes below. These cover how to use filters to achieve long exposures, even in bright conditions, how to create motion blur on water and how to use filters for fashion photography.