Using a long exposure when you photograph moving water can give you a lovely, creative image. Instead of recording the water sharply, as we would see it with our eyes, the movement of the water during long exposure creates a misty, white effect.
This can look fabulous with waterfalls, which turn into an ethereal stream of white. Or if you’re photographing at the coast, the waves of the sea around rocks or a pier can take on a smooth, almost ghostly appearance.
It’s not a difficult technique to do, either! You will need to have a camera which allows you to set the shutter speed and focus manually, and also a tripod. The tripod will be necessary because you’ll be using a long exposure, making it impossible to hand-hold the camera without getting camera shake.
Since the length of the exposure will be your main consideration with this technique, set the exposure mode to shutter priority. (For more about using shutter priority, see my blog on October 15th 2012). The actual shutter speed that you will need will vary from one situation to another, depending on various factors including the speed of movement in the water. Start with a speed of maybe ¼ sec, and review the result on the back of your camera. You can then increase or decrease the shutter speed, depending on the result you’re hoping to achieve.
Focus manually on your subject, as the autofocus may be confused by the movement in the water. If you can find a rock or something else static to focus on, that will probably make things easier!
Use a cable release to take the picture, so that you don’t jog the camera by pressing the shutter release button. An extra precaution is to use the mirror lock-up mode if your camera has one, to reduce any possibility of camera shake.
If there is a lot of white water, your camera’s meter may struggle to give the correct exposure, so it’s a good idea to bracket around the camera’s suggested reading. Rather than checking exposure by looking at the image on the back of the camera, check the histogram instead, to make sure that the distribution of tones looks right.
On bright days, you may have difficulty getting a long enough exposure. In this case, use a neutral density filter which will restrict the amount of light entering the camera, and allow you a longer shutter speed. If you don’t have an ND filter, then a polarising filter will reduce the light enough to give you an extra stop or two!