The Shutter Controls Light and Motion
Click to explore the various types of shutters used in digital cameras.
Click to explore the effect of shutter speed on exposure.
Katie turned a little just as the shutter opened causing unwanted blur in the image.
Click to explore how the shutter speed affects the capture of moving subjects.
The shutter keeps light out of the camera except during an exposure, when it opens to let light strike the image sensor. In respect to just exposure, faster shutter speeds let less strike the image sensor so the image is darker. Slower speeds let in more so it's lighter.
As the shutter speed gets slower, the image gets lighter. The reason you don't usually see this effect in your images is because when you or the camera change the shutter speed, the camera changes the aperture to keep the exposure constant.
In addition to controlling exposure, the shutter speed is the most important control you have over how motion is captured in a photograph. The longer the shutter is open, the more a moving subject will be blurred in the picture. Also, the longer it's open the more likely you are to cause blur by moving the camera slightly. Although you normally want to avoid blur in your images there are times when you may want to use it creatively.
To get faster shutter speeds increase the ISO. To get slower shutter speeds, use a neutral density filter.
A fast shutter speed (left) opens and closes the shutter so quickly a moving subject doesn't move very far during the exposure. A slow speed (right) can allow moving objects to move sufficiently to blur their image on the image sensor.
Although digital cameras can select any fraction of a second for an exposure, there are a series of settings that have traditionally been used when you set it yourself (which you can't do on many digital cameras). These shutter speed settings are arranged in a sequence so that each setting lets in half as much light as the next slowest setting and twice as much as the next fastest. Some of
the traditional shutter speeds are listed to the left from the slowest to the fastest speeds.
- Speeds faster than 1 second are fractions of a second and most cameras display them without the numerator. For example, 1/2 second is displayed as 2.
- Speeds of 1 second or slower are whole seconds and many cameras indicate them with quotation or inch marks ("). For example, 2 seconds is displayed as 2".
Many high-end digital cameras have added one or two stops between each of the traditional ones. This allows you to adjust exposure in one-half or onethird stop increments for finer exposure control. In the table to the left one-third and one-half stops are shown in red and blue respectively.