I’ve referred to shutter speed in previous articles, but for the sake of completeness I thought I’d write a quick entry on the subject.
What does ’shutter speed’ mean?
The term ’shutter speed’ refers to the time for which the camera shutter is held open while a photograph is being taken in order to allow light to reach the image sensor (or film in a non-digital camera).
Shutter speed is measured in seconds - on the Canon EOS 400D the available shutter speeds range from a maximum duration of 30 seconds (very slow) to a minimum duration of 1/4000th of a second (very fast).
Shutter speed and exposure
A slow shutter speed will potentially allow more light to reach the image sensor than a fast shutter speed. In order to correctly expose the photograph you need to balance the selected shutter speed with the appropriate aperture size. Basically, if you are using a slow shutter speed the shutter will be open for longer, so you should use a narrower aperture to avoid overexposure, whereas if you are using a fast shutter speed a wider aperture is needed to avoid underexposing the photo.
The relationship between shutter speed and exposure is useful to know about if you are trying to take a photograph in low light conditions where a flash would not be appropriate, for example if you were trying to photograph London at night. In this situation you would need to use a slow shutter speed so that the shutter will be open for as long as possible in order to allow the maximum amount of light to reach the imaging sensor.
Shutter Speed and Camera Shake
The slower the shutter speed the more likely it is that camera shake will occur since it is incredibly difficult to hold a camera perfectly still for even a second. Therefore if you want to use a slow shutter speed without compromising on picture quality you will need to use a tripod to keep the camera steady.
In September 2006 when I was still using my Nikon E4600 I took the following night shot looking out from Brighton Pier. I do not own a tripod, but improvised by resting the camera on the pier railings to hold it still enough to produce a relatively unblurred picture despite the 2 second exposure!
Shutter Speed and Moving Subjects
When you are photographing moving subjects/objects (e.g. moving cars or running water) the choice of shutter speed can make a real difference to the type of photograph produced.
Previously I only wanted to take photographs that simply capture the reality of my chosen subject and thereby preserve a scene or event for future enjoyment. However, whilst on holiday my boyfriend experimented with some of the settings on the Canon EOS 400D and produced some really interesting images - they no longer directly reflected reality, but were more ‘artistic’. Below you can see two pictures of the same stream in the Cairngorms taken by Nick using different shutter speeds:
Mountain Stream - Shutter Speed 1/60th second, Aperture f/7.1
Here you can see that the relatively fast shutter speed has produced a photograph which pretty much reflects how the stream actually looked. Additionally, you will note that due to the faster shutter speed the camera set a wide aperture of f/7.5 (see previous article on Aperture for explanation) in order to allow enough light onto the image sensor to produce a correctly exposed photograph.
Mountain Stream - Shutter Speed 1 second, Aperture f/36
Here Nick used a slow shutter speed and produced a really interesting photograph. The camera’s shutter speed was too slow to capture the individual movements of the streamwater, which has resulted in the blurred appearance of the moving water. I really like the effect - it gives the mountain scene more of an ethereal quality. I shall certainly be playing around with shutter speed in the future!
In order to minimise/avoid overexposure of the photo, the camera compensated for the slow shutter speed by selecting a very narrow aperture size (f/36). Since this aperture value is towards the maximum size available on my current camera setup, the photograph may be slightly overexposed, which would account for the slightly irregular colours.
