Using Shutter Speed to Control the Look of Your Photo
By Patty Hankins & Bill Lawrence
In the last newsletter, we talked a bit about changing the aperture to control depth of field. This time, we thought we would look at the other method of controlling exposure (for a given ASA): controlling the shutter speed.
For any particular level of light and ASA, either film or digital, proper exposure is a function of both the aperture (how much light is let into the camera), and shutter speed (how long the shutter is open to let light shine on the sensor or film). For every f-stop increase in aperture number (i.e. making the aperture smaller), the shutter speed has to be halved, i.e. the shutter remains open twice as long, to maintain the same exposure. So if you’ve determined that, say, a shutter speed of 1/100 of a second at an f-stop of 8 is a proper exposure, then a shutter speed of 1/50 of a second at f 11 would also give a proper exposure.
So as long as we’re maintaining proper exposure, why do we
care about shutter speed? The major reason to think about shutter speed is because of motion, either yours or your subjects. Often, we worry about shutter speed going too low, which could result in “camera shake” if you are hand-holding your camera, and could result in motion blur if your subject is moving – essentially your camera’s shutter is open too long to freeze the subject of the photograph. So, if you want to freeze the action of, say, sports or a fast moving animal, you want to have a very fast shutter speed. Also, if you are hand-holding a long telephoto lens, you will want a fast shutter speed since the magnification of the lens will magnify any accidental movements you make.
Other times, a slow shutter speed is desirable to convey a sense of motion in a still photograph. A common use of purposely setting a low shutter speed is to give a sense of flowing water – see the next article about photographing waterfalls for a good example of using this effect. We’ve also seen some impressive photos of palm trees in hurricanes where a slow shutter speed was used to blur the palm fronds and convey the sense of them whipping in the wind in a still photograph (sorry, we don’t have examples of these to show you – we try to avoid hurricanes). A slower shutter speed can also be used for a technique known as panning, where the photographer moves the camera to track a moving subject, which (if done well) results in a sharp subject but a background blurred by motion (this is a common technique for those photographing birds in flight and for those photographing racing cars).
To experiment with shutter speed, you will need a camera
that can go off of full automatic, and let you set the
shutter speed, either in full manual mode (you set both the aperture and the shutter speed), or in “shutter-priority” mode, which is an automatic mode where you restrict the camera to one shutter speed. A word of caution about shutter
priority: most camera lenses have less flexibility with the amount they can vary apertures (remember, this is the other part of getting a correct exposure) than your camera has with setting shutter speeds, so you have to make sure that you can get a correct exposure with the shutter speed you set. For example, if you try to take a photo on a dark night in shutter priority mode with a shutter speed of 1/1000 of a second, your camera will be unable to open the aperture enough to let in enough light for this shutter speed, resulting in an underexposure.
To experiment, simply find a subject that is moving, and try some exposures at different shutter speeds to see the results. Remember, for low shutter speeds, you will want a tripod to steady the camera. Visit our website for an article thatshows how different shutter speeds give different results for water flowing over waterfalls.
Patty Hankins & Bill Lawrence are the co-owners of Hankins-Lawrence Images, LLC, a digital photography company based in Maryland. HLI Photonotes, their monthly ezine, provides information and tips for photographers. To subscribe email firstname.lastname@example.org with subscribe in the subject or visit www.hankinslawrenceimages.com.
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