Circular polarising lens filter explained: When to use one?

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Hone your outdoor shots by discovering when a circular polarising lens filter comes in handy.

A circular polarising lens filter, or CPL filter for short, is an easy to use, screw-in filter that can alter the appearance of a photo. 

A CPL filter works by reducing the amount of light that reaches a camera lens. By twisting the filter in either a clockwise or anti-clockwise direction, you can adjust the light levels that are exposed to your camera, to create different image effects.

Landscape or outdoor photographers are particularly fond of the circular polarising lens filter, as it can reduce several unwanted effects, to enhance the colours, detail or drama of an image. Essentially, CPL filters can bring a mediocre picture to life, boosting its richness, vibrancy and contrast.

Gobe FiltersIMAGE—Pietro de Grandih
CUTTING REFLECTIONS

One of the most common uses of a circular polarising lens filter is to reduce reflections from non-metallic surfaces. Any outdoors photographer will be only too familiar with the irritation of reflections, particularly when it’s very bright or sunny. These reflections can easily distract from a photo’s subject. Sticking a CPL filter on your camera lens helps to kick bothersome reflections into touch. 

In particular, if you take photos of water or wet surfaces, the filter reduces scattered light and cuts out reflections of the sky or other objects on the water’s surface. This allows the detail of the water, including the surface below it, to stand out.

Photographers also find a circular polarising lens filter handy if they take photos through a window, or of glass buildings, as distracting light streaks and glare that infiltrate a shot can be eliminated. Photos of painted surfaces, such as vehicles or buildings, also create shine and reflections and can benefit from the use of a CPL filter.

A CPL filter will also reduce glare from reflected surfaces, creating clearer images. However, if you take photos of rainbows – which are caused by glare when the sun’s rays and moisture combine – turning the filter to increase the level of glare can actually enhance the colour and clarity of a rainbow.

Gobe CPLIMAGE—Luca Bravo
REDUCING HAZE

If you take photos where aerial or atmospheric haze affects an image’s clarity, a circular polarising lens filter can correct this and add contrast. Photographers who snap shots of distant scenes, such as mountain ranges or cityscapes, argue that a CPL filter reduces atmospheric haze. This can result in making faraway objects appear clearer and sharper.

Gobe CPLIMAGE—Matt Zhou
ENRICHING COLOURS

Since CPL filters block out certain light wavelengths, this means you can manipulate the colour effect of your photos to add more contrast. If you take photos of the sky, for instance, the filter can add a deeper tone to the blue, or make dull clouds appear more visually striking. 

However, if you use a wide angle lens, you might not get an even sky colour with a circular polarising lens filter. Therefore, stick to a lens no wider than around 24mm. Having said that, you might actually like the effect it creates, so it’s all a matter of personal opinion!

CPL filters also tend to work best during daylight, particularly on bright days. So, you’re unlikely to benefit from this filter if you take photos of sunsets or at night.

For photos of foliage or forests, the CPL filter can add saturation, vividness and contrast. It can transform nature into a richer and more verdant shade of colours. The filter can really come into its own during autumn, when nature’s hues are at its finest. A CPL filter can also banish reflections and shine from leaves, trees or plants, creating clear scenes free from distractions.

You can also use a circular polarising lens filter to create darker, richer or more intense tones. This is especially relevant if you want to add drama, atmosphere or even a sense of tension to an image. 

Experiment by rotating the filter to create the desired effect. Decide whether you want a scene to still feel natural, or maybe have a surreal edge to it. To achieve the maximum polarisation effect, shoot at an angle of 90 degrees from the sun or source of light.

IMAGE—Chris Poplawski
CIRCULAR POLARISING LENS FILTER VERSUS DIGITAL POST-PRODUCTION

Although post-production software can alter a photo’s colour, it can’t produce the same effects as a circular polarising lens filter. For instance, reflections and haze can’t be easily removed during post-processing. If you’re a landscape photographer eager to capture great photos, you’ll struggle without a CPL filter in your kit bag. In fact, when you use a circular polarising lens filter, you are effectively editing your images in real-time. This saves precious time by not needing to use post-editing software later on.

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