Blur moving water and create cleaner reflections with long exposures

As well as being useful for blurring clouds and removing tourists, strong ND filters are fantastic for blurring the motion of water. The churn is transformed into streaks of silky white blur. Notice too how reflections will come out clearer when the water is smoothed out with a long exposure. You don’t necessarily need a 16-stop filter for this: motion blur can be achieved with exposure times of just a few seconds. But with a strong ND, you’re free to use wider apertures. If you want maximum sharpness, you can set the aperture to the lens’s ‘sweet spot’, which is usually around 2-3 stops down from the widest aperture – around f/5.6 or f/8.