Shutter speed

The amount of light reaching the recording media (film or digital sensor) of a camera is determined by the size of the aperture that the light can pass through and the amount of time that the light has to fall on it.

The latter of these two factors is determined by the shutter speed used to take a picture. Of course, changes to the shutter speed will make large changes to the resulting picture obtained. It is important to realise that shutter speed will affect a lot more than whether a picture appears lighter or darker.

Let's consider that scenario first of all though:

Suppose you set your camera to automatic and take a picture of a building at dusk. As you see the scene, there will be a certain darkness to it that tells you it is evening time. The camera though will try to provide an even exposure; it does not know that you are trying to replicate dusk. It will increase the shutter speed to let more light in, and as a result will make your dusk scene look like day. (As an aside, it will also result in a blurred image, which we will go into a bit later). There are a number of ways to get around this:

The first way is to switch your camera to 'shutter priority' mode. This will allow you to control how fast the shutter speed is and adjust accordingly.

The second method is to tell the camera to under-expose the photo. There is generally an exposure compensation setting within the camera's menu system that will allow you to do this.

Finally, your camera may have a setting that tells it you are trying to take a picture in low-light levels and will make the camera behave accordingly. This can be found by referring to the manual of your camera.

Another effect of shutter speed is to freeze an image or allow it to blur. Particularly in motorsport photography, shutter speed is critical. If you use a very high shutter speed, the subject will be crisp but the picture may lack the drama of movement. If your shutter speed is too low, the image will appear blurred and of poor quality.

Water movement is a common area where shutter speed can dramatically affect the mood of an image. A fast shutter speed will capture every droplet and swirl in the water, whereas a slow shutter speed will allow the movement to blur into a general feeling of movement. These pictures generally have a calming air about them.

Shutter speed will determine whether your hand can hold a camera steady enough, or whether a support like a tripod (or a wall, piece of furniture etc.) should be used. As a general rule, shutter speeds above 1/125 of a second will require external support to avoid camera shake. The exception to this rule is if your camera has some form of image stabilisation which can help to keep an image sharp. If you are experiencing camera shake due to the low levels of light and are at the limits of what you can adjust with shutter speed (and aperture), then you may be able to use ISO to your advantage. Increasing the ISO will correspondingly decrease the shutter speed, as the sensor becomes more sensitive to the light that is hitting it. If using a film camera, this can be done by using a film with a higher ISO to begin with. The only problem with this solution is that increasing ISO value, results in more noise within an image. However, it is generally better to be able to take the image and accept an amount of noise, than missing the shot entirely.

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