(© Ian Plant) Although a photograph freezes an instant in time, there’s no reason that instant has to be a brief one. Many photographers strive for shutter speeds that will freeze the motion of their subject. I often prefer to take a different approach, opting for longer shutter speeds that reveal motion rather than obscuring it. Long exposure photography can show something different about your subject, and when done right can result in unique and compelling imagery.
The tools of long exposure photographers include tripods (always necessary but doubly so when working with shutter speeds of several seconds or minutes); neutral density and polarizer filters (both can reduce the amount of light reaching the sensor); and low ISOs and small apertures (once again, to reduce the amount of light reaching the sensor). Flash can also be an important component of long exposure photography, as a burst of flash will freeze some motion, whereas the long exposure for the ambient light will blur motion over time. This mix of stopped action and motion blur can be particularly effective with wildlife or people.
What shutter speeds are best? It depends, of course, on your subject and the amount of motion blur you wish to capture. Try to find the right balance between motion blur and texture—too much texture, and the subject will appear static, too little and you may lose all detail. The best way to find the “right” shutter speed (which is a subjective decision) is to experiment and review the resulting images on your LCD screen. Adjust ISO, aperture, and neutral density filtration as necessary in order to change your shutter speed until you find the best mix (remember, all of these are reciprocal to shutter speed, meaning that if you want to keep the same exposure but change your shutter speed you need to make a corresponding adjustment to one or more of these variables). Once you have everything worked out, you can concentrate on getting striking photos that will take your art to the next level.
So here’s my top five ways you can use shutter speed creatively:
Moving water: Try exposures between 1/4 second and two seconds to pleasantly blur the motion of water flowing down a stream or over a waterfall. When working on a lake or ocean with waves, experiment with longer exposures (30 seconds or more) to completely blur the moving water, giving it a pleasing misty look.
Wind-blown foliage: When high winds are blowing leaves, flowers, and ferns around, resist the temptation to stop the action with high shutter speeds. Try instead speeds between 1/2 and 30 seconds. These photos often look best if you have a few “visual anchors” in the image that do not move and are thus rendered sharp, such as rocks or large tree trunks that are not affected by the wind.
Moving clouds: Usually you need 30 seconds or more to blur the motion of clouds; sometimes several minutes might work best. As such, twilight or night is often the best time for moving cloud photography. The direction and character of moving clouds is important—try to photograph clouds that are moving towards you, as they will create radiating diagonal lines that can be pleasing compositionally.
Wildlife and people: Using long exposures with animals or people can produce interesting results, rendering them as an abstract blur if they are moving, or rendering their background as such if they are stationary and everything around them is moving. If you seek to introduce a little bit of motion blur in the flapping wings of a flying bird, for example, a relatively fast shutter speed of 1/30th or 1/60th of a second might work best. Keeping certain parts of the subject sharp, especially the eyes, can be effective but takes a lot of trial and error to successfully accomplish. As mentioned above, adding slow-sync flash can create a pleasing mix of stopped action and motion blur.
Stars: The movement of the Earth itself can be used to artistic effect, as at night it will cause the stars to appear to move across the sky, tracing patterns in the heavens above. Effective star trail photos can be made with exposures as short as ten minutes, or as long as several hours. By aligning your camera with the Earth’s axis (by pointing north in the Northern Hemisphere or south in the Southern Hemisphere), you can get attractive concentric circles. Long exposure noise that results when the sensor heats up can be especially problematic with star trail photography; mitigate noise build-up by shooting in cooler temperatures or by using your camera’s noise reduction feature.
P.S. I've got several recent entries on my personal photoblog that you might find interesting. I tend to blog about more personal (and less practical) topics there, but I've always got something that is good for a laugh or two. To keep up with my blog entries there and here you can subscribe to my blog feed, or follow me on Twitter or Facebook.