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Shutter Speed

The shutter speed also known as exposure time, is the length of time that a shutter allows light through the lens of a camera and onto the sensitive surface be it a digital sensor or piece of film.

It forms part of the Exposure  settings , alongside this are ISO  (sensitivity), and Aperture  (the size of the hole). These two and the shutter speed can all be changed so as to give the ideal combination for an exposure.

The agreed standard shutter speeds that should be present on all cameras are:-

• 1/1000s

• 1/500s

• 1/250s

• 1/125s

• 1/60s

• 1/30s

• 1/15s

• 1/8s

• 1/4s

• 1/2s

• 1s

Many cameras however go far further above and below this. The Nikon D300 for example going from 30 seconds to 1/8000.

The sequence of speeds used above are historically based in mechanical shutters. They can be considered as being 1 stop apart, each doubling or halving of the one above, although not exactly mathematically correct there are in effect three groups, 1 to 1/8, 1/15 to 1/60 and 1/125 and above. Today many think this has been retained in part because no one wants to be the one to change and partly as it is easy to remember, at least the upper and lower ranges, and you end up with a logical sequence of numbers. The numerical differences are proportionally small and should have no real affect on the exposures.

In addition to these you have one or more settings to allow longer time exposures to be made these are marked T for time or B for Bulb, the difference between these is that with Time (T) you press the shutter release twice once to open and once to close, while with Bulb (B), you hold the shutter release for the period of the exposure. These are located at the bottom end of the shutter range next to the slowest speed. You often have to set modern DSLR cameras to manual mode, before they show up. B is far more common on modern DSLR's than T.

To manage a longer time exposure you can use a special cable release with a timer built in or use the lock feature on the majority of cable releases. This lock feature is often a sliding mechanism so you press the shutter release on the cable and slide it to lock and slide it back to the release position to release the shutter.

Another way to get the effect of longer exposure is to add together a number of shorter exposures with the camera on a tripod, and many cameras have this ability.

Which shutter speed to use

There are a number of factors that affect the best shutter speed or shutter speed range that you wish to use, although often its the balancing factor that gets varied, without a lot of thought when you have already set the ISO and are selecting the ideal Aperture  or are using aperture priority mode on your camera.

The factors to consider are:-

Overcoming camera shake, when image stabilised or vibration reduced (VR) lenses are not being used. It is said that you should have at least the reciprocal of the focal length so 200mm at 1/200 second, 1000mm at 1/1000 second etc. With Vibration Reduction (VR) you have around a three stop advantage, so a 400mm without stabilisation would  need 1/400 second while with its 3 stop advantage you can chop this in half three times, 1/200, 1/100, 1/50. So the 400mm lens with stabilization can be hand held at 1/50 second.

Overcoming subject movement, this is the one area of photography that there is no precise rule on. The speed you need to stop movement is in relation to the movement of an item across the frame, so a snail slowly sliding across a macro shot may move exactly the same distance in the same time as a jet fighter in an aerial display when you are zoomed back and therefore need the same shutter speed to stop it. Something coming towards you will have little movement effect, while something going across the frame at the same speed has a far greater effect, with something going diagonally towards you at around half the speed of the one across the frame. Items coming towards you have little apparent movement until they get quite close and then their real speed becomes apparent, for example a train. Some items move very fast for example the wings of a small bird taking off.

Introducing motion blur, often you don't want to freeze everything, but instead want a little movement, the rule on this is that if something could exist in its position in true life you allow some movement, while when it cannot you can freeze it. So a horse going over a jump can be frozen in space as we know it could not exist in that state, while a footballer by a football we probably want a little movement on his feet and the ball to show its an action shot. With a racing car you pan with the car and press the shutter while panning and select a speed to stop the car, but with motion blur showing on the wheels and streaked background. Just shooting at a high speed would look like a parked car.

Water, one of the most frequent uses of shutter speed is in the representation of water. Water can be photographed a number of ways:-

• high shutter speed freezes the water, so icicle effect

• medium shutter speed produces normal looking water

• slow shutter speed produces appearance of more water, white froth effect on waterfalls etc See also Photographing Waterfalls,  How to photograph waterfalls 2 - shutter speed,  and Waterfalls Section

• very slow or long exposures, allows the mist effect pictures of sea water, as a number of waves and spray gets merged into one.

Light traces and fireworks, having slow shutter speed allows a light trace to be recorded, be it a cars headlights, a firework or with longer exposures the stars pattern caused by the earths rotation at night.

Zoom bursts, zooming with the shutter open on a time exposure creates an artistic effect.

Multiple images of a person at night or in a dark room. If you have the camera on a tripod and open the shutter, then firing a flash with a person in a range of positions, you have the effect of a number of copies of the same person. Before the time when you could do everything in editing this allowed many of the special effects to be produced.

Shutter Priority Modes

Most cameras have a shutter priority (S) mode, other common modes are aperture priority (A), programme (P) and manual (M). In shutter priority mode you set the shutter speed and the camera sets for you the aperture, using the information from your exposure metre. Exposure variation allows the image to be darker or brighter. Shutter Priority mode is most frequently used with sports and water photography. Manual being the preferred method for photographing fireworks and light traces.

Self Timer

Most cameras have a self timer facility, this allows the shutter to be fired after a delay. This is useful when you want to get into the photo, but is also useful when you want to fire the shutter without shaking the camera. Many cameras have the option to change the delay with a short period such as 2 seconds for this use.

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for details on Exposure Article Route see the Exposure  page