Camera Lens Filters Explained

Image by Misty Norman @mistynorman.au

Shot with Nikon D810 + Nikon AF-S 20mm f1.8G ED Lens, LEE Filters 0.6 ND Hard Grad Filter + LEE Filters Little Stopper @ f11, 15 sec, ISO 64<

What’s the secret to poster-worthy landscape photos? Or polished, professional architectural images? Or easy video exposure adjustments?

The answer is filters. And not the Instagram variety.

Lens filters are a key element to add to your camera kit if you shoot outdoors, regularly photograph in challenging light situations, film video, or simply want to protect your camera lenses. (For some lenses they’re actually an essential weather sealing component.)

The right filters can instantly elevate scenes from standard to spectacular. And they can spare you hours of fiddly photo editing, which actually undermines the detail and quality in your image files.

Filters come in a great many types, sizes and styles, each offering different benefits and possibilities. Read on to find out which filters are best for your lenses and what you want to achieve photographically.

• Filter Styles & Sizes 
• Filter Types & Uses:
• Clear Filters
• UV Filters
• Polariser Filters
• ND Filters
• A Note on Filter Quality 

Filter Styles & Sizes

Filters come in a variety of sizes and styles. The size will generally be dictated by the type of lenses you’re using. Very large or bulbous lenses may only be used with certain styles of filter (if at all). Otherwise, filter style is more a matter of preference regarding ease of setup, suitability for multiple lenses, and the amount of control you require.

Usually constructed from glass encased in a metal mounting ring, circular screw-on filters are the most popular style of lens filter. Simple to use, they screw directly on and off the front of lenses. They do occasionally get stuck, however, so care must be taken to prevent this. (Certain brands, such as B+W, are specially designed to resist jamming.)

Screw-on Filters

Usually constructed from glass encased in a metal mounting ring, circular screw-on filters are the most popular style of lens filter. Simple to use, they screw directly on and off the front of lenses. They do occasionally get stuck, however, so care must be taken to prevent this. (Certain brands, such as B+W, are specially designed to resist jamming.)

Rectangular Filters

Typically made of glass or resin, rectangular filters (aka square filters)—like those made by LEE Filters—sit parallel to the surface of the lens with the aid of special filter holders.

Square or rectangular filter systems typically require more components and setup time but, unlike screw-on filters, they work with lenses of different diameters (with the appropriate sized filter holder) and be oriented exactly how you want – perfect for precisely positioning the dark side of graduated ND filters. 

Some rectangular filter systems also lend themselves to being stacked so you can, for example, create both polarised and graduated ND effects in a single shot.

Drop-in Filters

Some lenses (particularly telephoto zooms with very large front elements) are designed to accept drop-in filters, which slot into a designated compartment towards the rear end of the lens. Drop-in filters are usually specific to a given make of lens but can often be used with lenses of different filter sizes.

Typically made of glass or resin, rectangular filters (aka square filters)—like those made by Lee Filters—sit parallel to the surface of the lens with the aid of special filter holders. Square/rectangular filter systems typically require more components and setup time but, unlike screw-on filters, they work with lenses of different diameters (with the appropriate sized filter holder) and be oriented exactly how you want—perfect for precisely positioning the dark side of graduated ND filters. Some rectangular filter systems also lend themselves to being stacked so you can, for example, create both polarised and graduated ND effects in a single shot.

Some lenses (particularly telephoto zooms with very large front elements) are designed to accept drop-in filters, which slot in to a designated compartment towards the rear end of the lens. Drop-in filters are usually specific to a given make of lens but can often be used with lenses of different filter sizes.

Filter Sizes

Different sized screw-on filters exist for different sized lenses, so you may require multiple sizes of the same type of filter depending on which lenses you own. (How do you choose the right filter size for your lens? A lens’ filter diameter is normally printed on the front of the lens and/or inside the lens cap.)

Alternatively, square or rectangular filter systems can be used for different sized lenses for a particular camera format (though different sized filter holders may be required, again depending on which lenses you own).

Neutral density (ND) filters are great for capturing long exposures like this photo of light trails | Image by Robert Tudor

What Filter Should I Buy for My Lens?

The question of how to choose a filter for your camera lens really depends on what you’re shooting and what you’re trying to achieve. Here’s a rough guide on what filter/s to get for various subjects/situations:

UV Filters

UV filters serve the same purpose as protective filters but also filter ultraviolet light. They help to reduce bluish casts (particularly in film cameras) and the image-degrading effects of atmospheric haze, both caused by UV light.

There are various grades of UV filters, all rated according to the amount and type of UV light they filter. Most UV filters are colourless but some have a slightly warm tinge to help remove blue casts and enhance contrast. Skylights, a pinker toned variety of UV filter, are recommended for portraits as they tend to be kinder to skin tones. Standard UV filters are ideal for other outdoor photos (like landscapes, cityscapes, sports, travel and wildlife) unless polarisation is desired – see below.

Top: Without polarising filter

Bottom: With polarising filter

Polarising Filters

Polarising (or polarizing) filters, aka polarisers, filter out glare-causing light while filtering in other ambient light. Popular for landscape and architectural photography, polarising filters reduce unwanted glare and reflections (e.g. from water and glass)—an effect impossible to simulate using editing software—while also enhancing contrast and colours (e.g. darkening blue skies).

Polarisers can be linear or circular – linear polarisers being simpler in design and suitable for mirrorless manual-focus cameras, and circular polarisers being rotatable and suitable for cameras with autofocus and/or a mirror mechanism (i.e. DSLRs). 

ND Filters

Standard neutral density filters are equally dark across their entirety and reduce the amount of light entering your lens by a set number of stops.

Standard NDs are mainly used to reduce your shutter speed or widen your aperture.

For Example: 

An exposure that, unfiltered, would require a shutter speed of 1/60 second can, with a 6 stop ND filter (ND64), be reduced to 1 second. A 10 stop ND filter (ND1024) could reduce the same exposure to 15 seconds. 

This can be used to show the effect of time and movement in your image, turning a waterfall into a smooth curtain or causing a bustling tourist destination to appear devoid of people. Alternatively, keeping the shutter speed high and widening your aperture can allow for shallow depth of field in bright sunlight situations.

Left: No filter | Centre: With LEE Filters 0.6 ND Hard Grad Filter | Right: With LEE Filters 0.6 ND Hard Grad Filter & LEE Filters Little Stopper | Images by Misty Norman

What Neutral Density Do I Need?

The actual filter density or ‘stoppage’ you need depends on how bright conditions are where you’re shooting, the speed of any movement in your scene, and the amount of motion blur you want to capture. Some experimentation may be necessary. But here’s a rough guide to ND filters recommended for various effects and times of day:

• 2 stop or 3 stop ND filter – Ideal for smoothing out seas, waterfalls or similar while retaining some texture. Also ideal for capturing light trails at blue hour and for using wide apertures (e.g. for portraits) in bright light.
• 6 stop ND filter – Very popular for landscapes; great for creating smooth clouds or water during golden hour 
• 10+ stop ND filter – Ideal for daytime (i.e. outside golden hour) shooting 

Standard ND filters are also useful for matching ambient background exposures with your camera’s flash sync speed – usually a quite low 1/200-250 second, for a more natural looking ‘fill’ light.

ND Filter Numbers Explained

ND filters are usually advertised by the number of stops they block (e.g. 3 stop ND filter), their optical density number (e.g. ND 0.9 = a 3 stop ND filter) or filter factor number – i.e. a digit equalling 2 to the exponential power of the number stops blocked (e.g. a 3 stop ND filter would be ND8, where 8 represents 23 or 2x2x2).

Infrared ND Filters for Neutral Colour Balance

Conventional ND filters block light on the visible spectrum. However, digital camera sensors are highly sensitive to (invisible) infrared light. A standard 10-stop ND filter, for example, lets through 1028x more infrared than visible light, resulting in noticeable (often magenta) colour casts.

While this is easily correctable in-camera or with editing software, you can save time by investing in infrared ND filters like the LEE Filters IRND range. These block both infrared and ultraviolet light, ensuring your camera will capture accurate, vibrant colours without the need for post-processing.

Variable ND Filters

Consisting of two pieces of polarising glass, variable neutral density filters are also equally dark across their entirety. But by rotating one side of the filter, you can adjust the degree of darkness (e.g. between 1-5 or 2-8 stops) to achieve fine exposure control. 

If you’re shooting stills, variable NDs permit wider apertures and slower shutter speeds in bright conditions. If you’re shooting video, variable NDs also permit wider apertures in bright conditions (giving you that cinematic look). They also let you adjust your shutter speed in sync with your frame rate, and so adjust to changes in lighting conditions.

Graduated ND Filters

Graduated neutral density filters are darker at one end of the filter and ‘graduate’ to clear at the other end.  They’re rated in both stops of light filtered (e.g. 1, 2, 3 stops) and how sharply (from ‘Soft’ to ‘Very Hard’ in the LEE Filters system) the filter transitions from its darkest to completely clear.

Graduated ND filters are used balance your exposure within a scene, usually between a bright sky and a dark ground, by placing the darker section of your filter across the brighter section of your image while allowing the darker parts to go unfiltered. Filters of different gradations, ranging from ‘Soft’ to ‘Very Hard’ (a very large gradation to an almost solid line respectively), are chosen based on how well defined the transition is between the differently exposed areas of your image. These might vary from undefined areas like woodlands or mist to very solid, straight separations, such as seascapes or the edges of buildings.

Image by Robert V Ruggier

What’s the Difference Between a Cheap Filter & an Expensive Filter?

Camera lens filters can vary greatly in quality; good ones preserve while bad ones degrade the quality of your images. The lower quality glass used in budget filters can cause a lot of problems, from lower light transmission—less light getting to your sensor—to increased lens flare, ghosting, chromatic aberration, uneven colour shifts, and even images that appear blurry or out of focus. Cheap filters are also less durable and (in the case of screw-on filters) more prone to get stuck on your lens.

Higher end filters (such as those made by leading brands like B+W or Hoya) are designed with professional photographers in mind.  They offer excellent light transmission—99% or above—and are multi-coated to prevent image degradation while at the same time offering resistance to elements like dust, water, greasy fingerprints, etc. Good quality filters are also much more durable (in the case of screw-on filters) unlikely to become jammed.

How Much Should I Spend on a UV or Protector Filter?

A good rule of thumb is to spend approximately 10% of the lens value on the filter – e.g. if your lens cost $2000, consider a protector or UV filter worth around $200 (as opposed to $20!). This way you can be confident that the quality of the filter is on par with the quality of the lens.

Find Out More

It’s remarkable what you can achieve with a good quality filter and a bit of know-how. To explore our filter range or find out more, feel free to browse our website or speak to our helpful photographers. 

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