The essential question is whether you want the water to be crisp and sharp, freezing its motion, or if you’re going for a dreamy, soft blurred effect. As shutter speed is the critical setting in either case, we recommend shooting in manual or shutter (time value) priority mode.
The opening photograph is a great example of when you want to stop water in motion. You need to use a relatively fast shutter speed. A safe bet is 1/500th of a second or faster. That may mean you need to open up to a large aperture, decreasing your depth of field, so pay special attention to your focus.
A favorite effect for waterfalls, streams and shorelines, the creamy, ethereal look of blurred water motion can add a softness that makes a nice contrast to sharper elements in the frame. For this effect, you need shutter speeds of one second or longer, so don’t forget your tripod—even the best stabilized lenses can’t help you here. If you’re trying to do this in bright conditions, you may not be able to select an aperture small enough for the very slow shutter speed you need. That’s where a neutral- density (ND) filter can help you reduce the amount of light coming into the lens, allowing for a longer exposure. ND filters are available in several densities. Try a two-stop filter for starters; if you plan to use this effect often, you may want to have a selection of ND filters at different densities on hand.
Bracket Your Exposures
Bracketing exposures is smart, especially when you’re experimenting with your technique. Start with the shutter speeds we’ve recommended, but take several additional shots, using slower and faster shutter speeds to greatly increase your chances of getting the effect you want. Use the outtakes as a learning tool: compare shots to see what worked and what didn’t.