How shutter speeds work

Shutter speed is one of the two basic controls in photography. It controls how long the shutter is open and hence the length of the exposure. The shutter speed also affects how the image will look and how sharp it is, so it’s not just a technical setting but an important creative tool too.

Shutter speed and aperture combinations

On a basic level, you use shutter speed and lens aperture together to control the amount of light. reaching the sensor to achieve the correct exposure. In many conditions you can choose different combinations of shutter speed and lens aperture to achieve the same exposure, so if you do want to use the shutter speed creatively, you’ve generally got some leeway to do this.

For example, in bright daylight your camera might suggest an exposure of 1/500 sec at f/8. However, all of the following combinations will give the same exposure:

So in bright light you’ve got lots of scope for increasing the shutter speed if you need to, depending on the maximum aperture of your lens.

In dimmer light you’ll find yourself working with slower shutter speeds. Sometimes you can compensate with faster lens apertures, but in general it’s the shutter speed that gives the most scope with lower light levels. See this article on exposure and how it works for more background.

Shutter speed and ISO in low light

If you’re shooting indoors or very late or early in the day, the light levels will be a lot lower, so you might get an indicated exposure of 1/30sec at f/5.6, for example. This means you’re working with slow shutter speeds, even with wider lens apertures. This is when you can start thinking about increasing the ISO setting to get back to more usable shutter speed and aperture combinations:

So as you can see, increasing the ISO is a way to keep shutter speeds high even in low light. You could also increase the ISO setting to allow smaller lens apertures at the same shutter speed, but in reality the ISO settings main advantage is to maintain usable shutter speeds and particularly to avoid camera shake. See ISO explained for more information.

Shutter speed and camera shake

If you’re shooting with the camera handheld, there will almost always be some degree of camera movement during the exposure. You can’t help it. Some photographers are better at hand holding that others, but there will always be some degree of camera movement. In a short exposure it won’t be visible, but the longer the exposure, the more likely it is that camera movement will cause blur. See this article on camera shake and how to avoid it for more.

You can work out so-called ‘safe’ shutter speeds from the focal length of your lens, so that with a 30mm lens, for example, your minimum safe shutter speed is 1/30sec, or for a 200mm lens it would be 1/200sec. It’s not that simple in practice because it depends on the photographer and the conditions, and whether the camera or lens has image stabilization.

The point is that the shutter speed you use is important in avoiding camera shake, particularly in low light, which is why you often need to increase the ISO setting. If you’re using a tripod, camera shake will not be an issue, so you won’t need to increase the ISO, just use longer exposures. But this introduces the second factor in choosing a shutter speed.

Shutter speed, subject movement and creative effects

You can use very long exposures to capture subject movement for creative effect. Many landscape photographers use ND (neutral density) filters in landscape photography to allow very long exposure times of seconds or even minutes, even in bright daylight. This blurs water and moving clouds for a dreamy, ethereal effect. If you want to capture moving traffic trails at night, you need a long exposure so that they appear as long streaks, or ‘rivers’ of light.

In these cases you’re looking at exposures of anywhere from 1-60 seconds or longer. You will need a tripod for this kind of photography.

On the other hand, maybe you want to freeze subject movement completely, in which case you need a very fast shutter speed. This is common when photographing sports, action or wildlife. 

Here, you might find yourself using shutters speeds from 1/sec right up to 1/8000 sec, and in many cases you might need to increase the ISO setting, particularly for indoor sports, just to make these shutter speeds possible.

Some cameras have electronic shutters which can achieve even higher shutter speeds, but these work in a different way and are not always good for fast action, introducing ’shutter distortion’ that can make fast-moving objects look skewed.

There are also situations where you might want just the right amount of ‘creative blur’, to show pedestrains moving across a wet city street at night, for example, or a train flashing past a station, or if you want to pan with a moving car to record the background as a blur.

It’s hard to be specific about shutter speeds in these circumstances, but you will typically be right at the edge of ‘safe’ shutter speeds and image stabilization will be a definite advantage. For moving pedestrians you could try shutter speeds between 1/15 and 1 second, while for panning shots 1/60 or 1/125sec can work well.