Long Exposures

Long Exposure photos

Shutter speed is a relatively easy-to-understand concept as it simply describes the time the camera lets light through to the sensor. When you press the button the camera's shutter opens and closes the mirror to let light through the lens and into the camera's sensor - when the shutter is released the shutter closes the mirror again and the image is then created in the camera's electronics.

Most standard cameras allow you to shoot with a fast shutter speed of 1/4000 sec to ∞ seconds (when using the BULB-function)

But what shutter speed should you use?

A short shutter speed means that we only gets a little light to the sensor - ie. the fastest shutter speeds are only useful in situations where there is sufficient light presented - eg. on a sunny day. Conversely, long exposure times of several seconds are only useful when there is very little light - otherwise you get a very overexposed image.

In addition to the exposure of the image the motive (or effect) must also be considered when choosing the exposure time. Is the moving subject or the subject is stationary? A moving vehicle requires a short shutter speed as you will get a blurred car if taken with a slow shutter speed as the car moves too far while the shutter opens. Conversely landscape images can easily be taken using a longer shutter speed, as the subject is stationary and therefore sends the same light rays to the camera when the mirror is opened at the beginning of the closing time as well as in the end.

However, this advice is not always the right ones - because you can also use the shutter speed to achieve special effects such as movement. This may, for example, be a moving car, which will result in the familiar light rays as shown below with a shutter speed of 30 seconds.

ISO 100     |    18mm    |     f/20   |   30"

Or you can use the shutter speed to express the movement of the subject by panning the camera while taking the picture. By following the subject it will be able to obtain a sharp subject against a background where the shutter speed has smeared the light as shown below

ISO 100     |    50mm    |     f/1.8   |   1/25"