CLOUD BURST

Add drama to any sky with an ND filter

Light is essential for every photograph, but sometimes there’s more than you need. By restricting the flow of light into your camera, neutral density (ND) filters enable you to use longer shutter speeds. And longer shutter speeds can have a stunning effect on motion, transforming water or clouds into beautiful, milky blur.

Under normal daylight conditions your camera will struggle to achieve very long shutter speeds. Even with the lowest possible ISO and narrowest aperture you'd be unlikely to get a speed slower than half a second without over-exposing your shot.

This is where lens-mounted neutral density filters come in. They work simply by restricting the amount of light that enters your camera, and they come in different strengths, measured in 'stops'. For every stop of light blocked by the filter you're able to double the shutter speed and still take a correctly-exposed photograph.

Is this your stop?

So what strength of filter is right for you? This will vary from subject to subject, and depends on the speed of the objects you wish to blur and the brightness of the scene. When we shot our windmill image, our aim was to capture the movement of the clouds. In strong winds you might only need a shutter speed of second or two to capture good cloud blur, and that can

In strong winds you might only need a shutter speed of a second or two to capture good cloud blur, and that can usually be achieved with a three- or four-stop ND filter

usually be achieved with a three- or four-stop ND filter. But on a calm day, when the clouds are taking longer to drift across the frame, a longer shutter speed, and therefore a darker filter, is usually required.

At the extreme end of the filter scale, there are 10-stop filters (sometimes referred to as ‘Big Stoppers’, although that’s actually the name of the famous Lee Filters version). These enable you to multiply your exposure time by a thousand, sending your shutter speeds well into the minutes.

Blurred motion is often most effective when contrasted against a subject that anchors the frame, so we went to Wilton Windmill in Wiltshire for our skyward shoot. Read on to find out how you can give your landscapes a similarly atmospheric edge by transforming passing clouds into gorgeous silky blur.