Q) I see all of those neat shots of waterfalls, where the water looks so strange. How can I do that?
Scott D., Rochester, NY
A) What you’re seeing is water captured with a slow shutter speed. If you want to do that yourself, first you need to use a tripod, as the slow shutter speed requires a firmly supported camera.
Because you’re using a slow shutter speed, you’re letting a lot of light onto the sensor. You need to compensate for that shutter speed, so set your ISO as low as possible and stop down your lens. But many times, this won’t be enough to reduce the amount of light coming into your camera. You may need to add a neutral-density filter to your lens. A polarizer will take down some of the light, too.
Speaking of polarizing filters, some photographers use a filter that’s two polarizers mounted back to back. This gives you essentially a variable neutral-density filter, so you have a lot of control over which shutter speed you use.