Shutter Speed

Shutter speed, or exposure duration, is quite simply the amount of time for which light is allowed to enter the camera.  When you press the button to take a photograph a ‘shutter’ at the front of the lens opens and light can enter the camera. After a set amount of time the shutter closes again and the light is shut off. How fast this happens is called the “shutter speed”.

Shutter speed is measured in seconds, and on your camera you will usually see this as a number representing a fraction of a second.  To shoot with shutter speed it’s a good idea to use “S” mode – as discussed before this will allow you to manually adjust the shutter speed while the camera automatically adjusts the other settings to keep the exposure at a good value.  You can also use “M”, but here you will be responsible for all settings, not just shutter speed.  How you adjust the shutter speed can depend on your camera model.  Normally you will have a small wheel that you turn to increase or decrease the exposure duration.

The most important use of shutter speed is capturing motion. If you set a shutter speed to 1 second, for example, the camera will capture all the light that enters the camera over a 1 second period. That’s fine if the image is static, but if something is moving in the image then that object will appear blurred in the final photograph.

The boat has moved during the exposure, causing it to look blurred in the photograph

To capture fast moving objects you will want to reduce the shutter speed as much as possible.

Controlling the shutter speed allows the photographer to choose how motion is shown in an image. This can have particularly interesting results when photographing moving lights (especially at night), moving water or even the night time sky. Showing a fast moving object as slightly blurred in a photograph also helps to convey the impression of speed to a viewer.

An example of light trails caused by moving a camera during a long exposure.

Another good reason to pay attention to shutter speed is to reduce the effect of shaking and vibrations. Most of the time you will take photographs by holding the camera in your hands. Unfortunately humans are not very good at remaining still enough to avoid blurring with long exposure times. It varies from person to person but for most people any exposure longer than 1/10th of a second will start to be blurred from shaking. This problem can be reduced by using vibration reduction (VR) technologies, by finding a stable surface to rest the camera on, or by using a tripod.

In cases where you use a tripod or other stable surface it can be useful to introduce a short delay between pressing the camera button and beginning the exposure, as this helps reduce any vibration caused by pressing the button. Most DSLR cameras will have an option for a 2 second delay before the exposure begins. It’s also possible to trigger the exposure using a remote control if you camera has, for example, a bluetooth receiver.

A long exposure during low light levels can dramatically increase the quality of night time photography. To capture this photograph an exposure of 1 second was used.

Shutter speed also helps control the overall exposure. The longer the exposure duration the more light will be able to enter the lens. This can be especially useful when photographing in low light levels, where a long exposure can help make an otherwise dark scene look bright.  This is also why it’s important to use a tripod to hold a camera steady for night photography.

Stops

In photography “stop” is a commonly used term. A stop means a doubling or halving of the exposure (and so the brightness) of an image. We can say that we increase the shutter speed by “one stop” – this means that we double the shutter speed and so double the exposure. Two stops would mean we double the shutter speed twice, giving a 4 fold increase in exposure. We can also decrease the shutter speed by one stop, and this would mean we halved the shutter speed.

Stops are also used when we discuss aperture (which we will in the next lesson). Why? Because both aperture and shutter speed are ways of controlling the exposure of the image. If we increase the aperture by one stop and then decrease the shutter speed by one stop the exposure at the end will be exactly the same as at the beginning. This key relationship between shutter speed and aperture is important to be aware of.

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