An insightful account detailing the main differences between a polarising filter and an ND filter.
Polarising filters and ND filters help the landscape photographer deal with challenging light conditions to improve image quality. However, they are not the same. They perform different functions to address separate issues in photography. Therefore, it wouldn’t make sense to restrict yourself to using just either a polarising filter or an ND filter.
Both of these filters are made from thin pieces of protective glass that are easily attached to a camera lens. Yet, this is where the similarities end.
A polarising filter is like a colour filter for your lens that you can rotate to block out light from a specific direction. This can boost colour contrast and saturation, thus making dull objects appear more vivid. If you’ve ever seen photos of deep blue skies and striking clouds, it’s likely that a polarising filter was used. By reducing overall exposure, the photographer can darken an image, adding intensity and clarity to a scene.
A polarising filter reduces glare and reflections on non-metallic surfaces, such as water or rocks, or when shooting through glass. It can also remove shine on foliage and make water appear transparent.
Polarising filters work best when shooting at a 90-degree angle to the sun. Since these filters only remove light that’s polarised in a specific direction, they don’t work well with wide-angle lenses. This is because these lenses collect light from various directions. This can cause uneven light distribution in an image, such as the sky appearing darker in some parts than others.
A neutral density (ND) filter differs from a polarising filter in that it doesn’t have any impact on the colour of your image, but it excels at blocking out light.
This transparent filter reduces light exposure entering your camera lens. This allows you to shoot using wider apertures and longer exposures, without overexposing an image in bright conditions. You can control how much light you want to block from your camera lens with different filter strengths or densities. Filter strengths are represented by f-stops.
A photographer will find an ND filter useful to achieve a balanced exposure between an image’s foreground and background. In bright light, this filter produces a shallow depth of field by reducing light exposure with a wide aperture. This won’t overexpose your scene.
An ND filter can help to slow down a scene with slower shutter speeds so that you can introduce a sense of movement to water and clouds. If you’ve ever seen photos of waterfalls or bodies of water that have an intriguing, silky, smooth, blurred effect, or moving objects such as people or vehicles appear blurred to convey surreal motion, these effects will have undoubtedly been achieved by using an ND filter.
Polarising filters and ND filters have separate jobs to do in photography, but if you want the best of both worlds, they can be stacked together, but do proceed with caution so that you don’t end up with unrealistic or very dark shots.
Whether you use a polarising filter or an ND filter, or both, knowing how to use them correctly can greatly influence their efficiency and the quality of your images. With the right application, they can enhance your photos, making them richer in colour, more vivid and realistic, or even arty and surreal. Always remember the golden rule of choosing filters – opt for the highest quality filters you can afford.