One of the great joys of DSLR photography is controlling your shutter speed – which will have a big impact on your photos when there’s something moving in shot.
Using a fast split-second shutter speed of 1/1000 sec will freeze most movement, such as the waterfall in our scene. Whereas slowing the shutter speed down, any movement becomes blurred. The slower the shutter speed, the more the gushing water turns milky, helping to capture a sense of movement in the waterfall.
There are a few techniques you can use to obtain the longest possible exposure. Shoot in overcast conditions if shooting in daytime – or shoot before first or after last light. Select a narrow aperture to minimise the amount of light reaching your DSLR’s sensor, such as f/16, and use the lowest possible ISO setting on your camera. But adding an ND filter will really slow down your shutter speeds… even when shooting in daylight.
Video tutorial: How to use ND filters for long exposures during the day
Step by step: Capture atmospheric shots of moving water with long exposures and Neutral Density filters
1: Camera & lens
For this project we shot a picturesque waterfall that has fast-flowing water: ideal for a long-exposure shot. We’re using a full-frame Canon EOS 5D Mark III and shooting at a mid-range focal length on our Canon EF 24-70mm standard zoom lens. But any camera and standard zoom will do.
2: Tripod & remote control
A tripod is essential for long exposures. If you shoot handheld with a slow shutter speed, you’ll get very shaky shots! We’re also using a remote control, as the act of pressing the shutter button can cause camera movement and unwanted blur.
3: Best shooting mode
We’re shooting in Av mode with a narrow aperture to control depth of field for our scene. It’s best to shoot at f/16 (rather than f/22) for optimum image quality, while still reducing the light reaching our sensor for the slowest possible shutter speed.
4: Low ISO setting
Choose the lowest ISO setting available on your camera. On our 5D Mk III we can shoot at ISO50 (the Canon 5D Mk IV, 5DS/R, 6D Mk II and 1D X Mk II also allow this) one stop slower than ISO100. But, even then, we could only get a shutter speed of 1/15 sec. Quite slow, but not enough for really smooth waters.
5: ND filter for 30 second exposures
An ND (or Neutral Density) filter is crucial as these dark filters block light reaching our sensor: extending our exposure, and increasing blur in moving water. NDs come in various strengths from 1-stop, 3-stop, but as it was daytime we used a B+W 1000x (10-stop) ND filter.
This enabled us to shoot at 10 stops slower than 1/15 sec, which would be a 1-minute exposure time. But we also dropped the aperture to f/16 for better image quality, as at f/22 diffraction can cause sharpness to drop off at the edges.
Therefore our shutter speed was 30 seconds. This captured lots of lovely blur in the rushing water, and at that length of exposure, it’s captured a little movement in the clouds, as well as making the slower-moving water on top of the weir appear glassy and serene.
6: Compose and Expose
As we’re in Av mode, with our ND filter on, our camera will simply adjust the shutter speed for a good exposure. Shooting in Live View with exposure simulation means you can see still your scene on the LCD too, ideal for when composing and focusing.