•** Use a larger f-stop.** Sometimes there’s too much light to use the large f-stop you want to work with (in order to reduce depth-of-field). Add an ND2 or ND4 filter, and f/2,8 or f/2 is available to you.
• Use the slow shutter speed you want. A ND filter can give you the half-second to several-second exposures you need for cool-looking silky water effects.
• Make moving objects vanish. The moving cars and people in your scene distract from the image of the building you're trying to capture. Try a ND8 (or stack several filters), use a tripod and a 30 sec exposure.
•** Balance the sky and foreground.** In most scenes, the sky is much brigher than the foreground. A split ND filter, with the dark portion on top can even out the exposure of the two halves, making those washed-out clouds visible again.
Adapted from Digital SLR Camera & Photography for Dummies by David D. Busch (Wiley, 2007, $30)