Shutter Speed in Digital Photography
Three main areas that you can manually adjust and determine the exposure of your shots are: Shutter speed, Aperture and ISO. In this post we explain about shutter speed and in next posts we will explain about Aperture and ISO.
What is shutter speed and what does it do
Most basically defined: Shutter speed is the amount of time that you give the shutter to be open and your image sensor sees the scene that you want to capture.
Shutter speed is measured in seconds – or in most cases fractions of seconds. The bigger the denominator the faster the speed (1/1500 is much faster than 1/60) anything slower than 1/60th of a second causes camera shake. Camera shake is when your camera is moving while the shutter is open and results in blur in your photos.
If you’re using a slow shutter speed (anything slower than 1/60) you will need to use something to avoid camera shake, a tripod as an example.
Shutter speeds available on your camera will approximately double with each setting. As a result you will usually have the options for the following shutter speeds: 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8 etc.
When thinking the use of shutter speed in an image, we should ask our self whether anything in our scene is moving or not and how we’d like to capture that movement. If there is a movement in our scene we have the choice of either freezing the movement (so it looks still) or letting the moving object intentionally blur (giving it a sense of movement).
To freeze a movement in an image (for example somebody is running) you should choose a faster shutter speed and to let the movement blur you should choose a slower shutter speed. The actual speeds you should choose will vary depending upon the speed of the subject in your shot and how much you want it to be blurred.
In the photo below to freeze the movement, I chose 1/2500 of shutter speed when she was jumping :
There are times when motion is good. For example when you’re taking a photo of a waterfall or seascape and want to show how fast the water is flowing or when you’re taking a shot of a racing car and want to give it a feeling of speed, or when you’re taking a shot of a starscape and want to show how the stars move over a longer period of time. In all of these instances choosing a longer shutter speed will be the way to go. However in all of these cases you need to use a tripod or you’ll run the risk of ruining the shots by adding camera movement (a different type of blur than motion blur).
Focal Length and Shutter Speed: Another thing to consider when choosing shutter speed is the focal length of the lens you’re using. When we choose longer focal lengths, we will need to choose a faster shutter speed. Longer focal length will accentuate the amount of camera shake, unless you have image stabilization in your lens or camera.
If you want to shoot with the focal length of 70mm, at least 1/80th is good, but if you shoot with 200mm lens you will need at least 1/250th shutter speed.
Remember if you change shutter speed you’ll need to change Aperture or ISO to compensate for it.
If you speed up your shutter speed one stop (for example from 1/80th to 1/100th) you’re effectively letting half as much light into your camera. To compensate for this you’ll probably need to increase your aperture one stop (for example from F16 to F14). Also you may need to choose a one stop higher ISO rating (for example from ISO 250 to ISO 320.