Anytime you’re presented with a moving subject a photographer really has two options. Firstly they can freeze the motion by using a fast shutter speed and secondly they can catch and enhance the motion by using a longer shutter speed that blurs the moving element in the shot (in this case — water).
Most photographers choose the second option and permit the water to blur. Here’s how to do it. You’ll want your digital camera and a tripod. It will also be helpful to have a polarizing filter if you have one.
Before you begin experimenting, switch your camera to auto mode, ensure your flash is turned off and have a shot of the waterfall. As you do — take notice of the exposure that the camera sets. Your camera will almost certainly choose an exposure that freezes the water somewhat. This photo will be a tiny reference point to compare your shots to later and to use as a basis for your exposures.
Switch to shutter priority mode in your camera (we’ve talked about shutter and aperture priority modes previously). Generally you’ll want to attempt to have a shutter speed of 1 to 2 seconds to get a nicely blurred water.
Of course to take a shot at a shutter speed of this length you’ll definitely need a tripod or some other way to make certain that your camera is completely still for the complete time that the shutter is open.
The problem with increasing the shutter speed is that it increases the quantity of light that gets into your camera and unless it is quite a dark and gloomy day you will find your image is going to be over exposed (although in shutter priority mode the camera will select a very small aperture to try and compensate for it).