In a previous article, we talked about the first element of exposure: ISO. After setting ISO on your digital SLR camera, your next step in setting the “correct” exposure will be to adjust for either Aperture or Shutter Speed depending on the priority of the subject you are photographing. Let’s start with shutter speed. Shutter speed is one of the elements of exposure that is key to gaining creative control in digital SLR photography.
Shutter speed is the amount of time the lens will stay open when you click the shutter button.
More specifically, it is the amount of time the shutter will stay open to allow light to hit the image sensor.
Shutter speed therefore determines how much light hits the image sensor. The longer it stays open, the more light hits the image sensor. And conversely, the shorter the shutter stays open, the less light that will hit the image sensor.
It is important to understand that shutter speed is not only used to set exposure. It is also an important element in achieving creative control over your photography. When you begin to understand shutter speeds and how it relates to the other aspects of exposure, you begin to move into the territory of creative photography and away from simple “picture-taking”. Like aperture, shutter speed can be used to “manipulate” the subject in ways that allow you to express more about that subject than what is already obvious.
Shutter speeds are measured in both fractions of a second and full seconds. Depending on the digital SLR camera, these times can be as fast as 1/8000th of a second and as slow as 30 seconds. On your DSLR, the times will generally look like this:
1/8000, 1/4000, 1/2000, 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1, 2, 4, 8, 16, 30
Remember that a full “stop” represents either a doubling of the amount of light entering the camera or that same light being cut in half. With the above shutter speeds you should notice that as the times move to the right the times double and the shutter speeds get slower. This doubling represents a full “stop” increase in exposure, meaning that the amount of light hitting the image sensor is doubling.
When we move to the left, the times are being cut in half and the shutter speeds are getting twice as fast. This cutting in half of the time the shutter speed is open represents a full “stop” decrease in exposure, meaning that the amount of light hitting the image sensor is being cut in half.
Keep in mind that today’s digital SLR camera will allow you to set your shutter speeds in 1/3rd stop increments. Therefore three “clicks” of the dial will represent one full stop. Also, in most cameras, the shutter speeds will be shown as a single number. So, 1/250 will be shown as 250.
Some important points regarding shutter speed:
- Shutter speed is generally used to control movement. When you wish to freeze motion, you would use a very fast shutter speed. When you wish to show movement by blurring objects, you would use a slow shutter speed.
- The slower the shutter speed, the greater the risk of blurred images due to camera shake. The general rule of thumb is to limit your shutter speed to “1/focal length”. For example, if you are shooting at a focal length of 50mm, you should not set your shutter speed slower than 1/50th of a second. There are ways around this rule. One way is to use a tripod. Other way is to use a DSLR or DSLR lens with an image stabilization system that will allow you to hand-hold the camera at much slower speeds than the rule-of-thumb suggests.
Here is a graphic summarizing the effects of shutter speed:
The most important point regarding shutter speed is that it cannot be used in isolation. Any change in shutter speed away from the correct exposure setting will require an opposite change in either aperture or ISO. This is discussed in greater detail in the article Understanding Exposure – Bringing ISO, Shutter Speed & Aperture Together
Now let’s move on to Aperture.
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