A guide to getting the right shutter speed

'What shutter speed should I use?' is one of the most frequent questions I hear from photography students. The trouble is, the answer is not straightforward and usually runs along the lines of 'well, it depends on what you're trying to achieve.'

It may not seem very helpful, but unfortunately, it's pretty much correct: there is no single shutter speed that is correct for any given situation.

The original question itself reveals a lack of understanding about what the shutter speed is all about and how it can be used in different ways to achieve a range of effects. It's not just a question of flipping the shutter open for a fraction of a second, but of using it to influence the creativity of your photography: should I have a fast shutter speed to freeze movement or a slow one to blur it, to provide a big depth of field bringing most of the view sharply into focus, or a shallow depth of field to leave most of it out of focus?

In this article, I'm going to delve into a host of different aspects surrounding the 'correct' and/or 'creative' use of the shutter and the length of time it stays open, and the effects this can have on the exposure, the technical nature, the mood, and the artistry of the final image.

 

Delivering light

 

The first and overriding consideration surrounding any decisions about the shutter speed is the need to deliver the right amount of light to the camera's sensor to have any hope of obtaining a useful image.

The amount of light travelling from the outside world, through the lens, to the sensor is controlled by the shutter speed and the lens aperture (the f-number). The sensor's sensitivity to the light is governed by its ISO setting. Usually, this three-way balance is most easily understood and controlled by fixing the ISO at a single setting, usually at quite a low sensitivity (often 100 on the ISO scale). This simplifies calculations, ensuring that the correct exposure is down to a two-way balance between shutter speed and lens aperture.

At a fixed ISO, the right amount of light needed is more or less the same for any given sensor, regardless of the time of day or night. So, is the big wide world providing too much light to expose the sensor or not enough?

In the middle of the day, there’s a huge amount of light available—even if the sun isn't shining—meaning that the shutter and lens aperture have to work together to cut down the amount of light reaching the sensor, the shutter firing at high speed, and the lens aperture closing down to a pinhole.

On the other hand, there won't be enough light available at night. For enough light to reach the sensor, the lens aperture needs to be wide open, and the shutter needs to stay open for a long time.

For most scenarios (except perhaps in the dead of night), the camera's exposure meter tells the photographer very accurately what shutter speed and lens aperture will deliver the right amount of light, resulting in a good exposure and a well-lit image.

However, there isn't just one shutter speed and lens aperture setting for each lighting situation, but a whole series, reflecting a balance that must exist between shutter speed and lens aperture to maintain the correct exposure. Increase one, and you'll need to decrease the other to maintain the balance, otherwise, the image will come out badly under-exposed (i.e. too dark) or over-exposed (too bright).

With the ISO fixed at 100 on a bright sunny day, a typical correct exposure is with a shutter speed of 1/125th second and a lens aperture of f/16. Such a shutter speed and lens aperture combination will give a well-exposed image. But, if you halve the shutter speed to 1/60th second, doubling the amount of time the shutter is open, you must also halve the size of the lens aperture to f/22 (the higher the f-number, the smaller the lens aperture) to cut back the light. Similarly, if you double the shutter speed, halving the length of time the shutter is open to 1/250th second, the size of the lens aperture would need to double, to f/8, to compensate.

So, you end up with a whole series of shutter speed/lens aperture combinations that together will result in a good exposure. However, they also have further effects on the focus and crispness of the final images that—when you start to shoot creatively—become vital in your decisions concerning what combination to choose to achieve what effect.

For example, if you're shooting some fast-moving action, such as sport, you may well want to use a fast shutter speed to freeze the movement, but this will come at the price of having to have the lens aperture wide open (i.e. a low f-number), resulting in a small depth of field (i.e. less of the image scene will be in focus).

Conversely, when shooting a landscape, it’s common to try and get everything in the image sharply in focus, which requires a large depth of field—in other words, a narrow lens aperture/high f-number. To do this while preserving the lens aperture/shutter speed balance, use a slow shutter speed. That may mean putting the camera on a tripod.

To some extent, you can make the confines of the lens aperture/shutter speed balance a little easier by increasing the sensor's sensitivity to light. In other words, you can put the ISO up. This is great for convenience, and especially when photographing action in poor light, it might be the only way to obtain a well-exposed image. However, always remember that as the ISO increases, the image quality decreases, so if the quality is important to you, increasing the ISO should only be a last resort. Don't do it out of laziness!

 

Automatic versus semi-automatic and manual photography

Of course, if you shoot in a fully automatic mode, your camera sorts all this out for you, itself choosing what it believes is the best shutter speed/lens aperture combination (and perhaps also ISO) for the kind of photo it believes you're taking.

However, although a reliance on a fully automatic mode is fine within certain limits, it seriously curtails your creativity since it ensures the camera is in control of your photography, not you.

To put you in the driving seat and make the camera your tool rather than your master, you need to take control, which means shooting in either a semi-automatic mode or fully manual. Semi-automatic means shooting in either shutter-priority or lens-aperture modes. In the former, you choose the shutter speed, and the camera chooses what it believes is the right lens aperture to provide the correct shutter speed/lens aperture exposure balance. With aperture-priority, you choose the lens aperture, and the camera provides the correct balancing shutter speed.

In fully manual mode, you can manually select both shutter speed and lens aperture. This sounds like you can use any combination, but it doesn't. You are still constrained by the required shutter speed/lens aperture balance to provide the right amount of light to the sensor. The camera's exposure meter will tell you what it thinks are the right combinations of settings, but you’ll have to apply those settings yourself—the camera won't do it for you.

 

Getting creative

Getting creative and being in control of your photography means that you have to ask some questions before each and every shot to work out what you're trying to achieve and how to achieve it.

One of the first questions is whether you're going to hand-hold the camera or set it up on a tripod. The former is quick and convenient, but it restricts your choice of shutter speeds as you’re forced to use one that’s fast enough to result in no camera-shake in the final images. In other words, it has to be fast enough to prevent blurring of the images as a result of the hand's inability to hold the camera still.

Clearly, the slower your shutter speed, the more likely you are to see camera shake in the final images. Similarly, using a telephoto lens magnifies any camera-shake present, while a wide-angle lens will minimise it. So, the longer your focal length, the faster the minimum shutter speed you have to use to overcome camera-shake.

A rough rule of thumb is that the slowest useable shutter speed for hand-held photography is the reciprocal of the focal length of the lens in use. In other words, if you're using a 30mm lens, the slowest shutter speed you can use without risking camera-shake is 1/30^th of a second. On the other hand, that jumps to 1/300^th second for a 300mm lens. This applies to lenses without image stabilisation/vibration reduction, so if you're able to add the effect of that in, then you can bring those minimum shutter speeds down significantly—though it will always remain a vital consideration.

Shooting in this way is all very well and good if you're happy with having to use a relatively fast shutter speed, but if your creative photography (or indeed poor light level) requires you to use a slow shutter speed—such as to deliberately blur moving components of a scene—then you absolutely must put the camera on a tripod. There is no short-cut!

 

Creative scene options

The final section of this article will highlight a few scenarios that illustrate several different shutter speed selections for different creative situations.

 

Fast-action photography

In photography, where there’s a lot of action, such as sport or wildlife photography, it’s common to want to freeze the action, to capture one single moment in time. For this, you’ll need a fast shutter speed, typically over 1/250^th second and often faster. Even if using a strong telephoto lens, this often means that a tripod is unnecessary, giving you greater flexibility to move the camera around quickly if need be.

It also means that, in maintaining the shutter speed/lens aperture balance, the latter will have to be quite wide open (i.e. a low f-number) to compensate for the fast shutter speed. This will result in a shallow depth of field, meaning that all the background will be blurred. This is often good news as it ensures that your subject will stand out strongly from that background, making it clearly the photographic subject of the image. It does also mean, however, that your focus had better be pretty accurate to ensure that it really is on your intended subject and not something just behind them!

Having said all this, there will be times in creative photography when you might want to blur the movement. This will, of course, mean using a slower shutter speed, though exactly how slow is difficult to generalise about, as it depends on how fast your subject is moving: speeding cars will blur at a much faster shutter speed than a running man, for example. Obviously, once that shutter speed drops to a certain level, the camera must be mounted on a tripod.

 

Portraiture

In the classic head-and-shoulders type of portraiture, the emphasis is entirely on the subject's face: the last thing you want is anything behind the subject, causing distraction. This can be overcome not only by having a simple backdrop but also by ensuring that everything behind the subject is totally out of focus. This is achieved by using a fast shutter speed, resulting in a wide lens aperture (i.e. a low f-number) and hence a small depth of field that ensures that most of the image is out of focus. Once again, be sure that your focus is accurately on the subject's face, especially the eyes, otherwise, they may come out blurred too!

 

Landscape photography

In most forms of landscape photography, the scenes being photographed have a lot of three-dimensional depth, most of which needs to be sharply in focus for the final images to be successful. To achieve this, a large depth of field is needed, something normally managed through a combination of a wide-angle lens and a narrow lens aperture (high f-number). That narrow lens aperture results in a slow shutter speed, so it’s often necessary to mount the camera on a tripod in landscape photography, particularly when shooting at the beginning or end of the day when light levels are low.

 

Moving water

Few things are more effective at creating mood and the sense of movement in an image than flowing water: the photographic results can be truly magical. There are essentially two ways to photograph it successfully: with a fast shutter speed to freeze the movement or with a slow shutter speed to blur it out.

The former is particularly effective when shooting surf, or foaming water in a river, when a fast shutter speed can freeze water droplets mid-air, capturing the sense of energy and power. Unfortunately, it is often shot badly. To start with, you need to hone in quite close to such water using a telephoto lens to really emphasise the flying droplets. Moreover, the water is usually moving a lot faster than most people realise, necessitating the use of a shutter speed of at least 1/500^th second, often more, to fully freeze that fast movement. This will result in a wide lens aperture and hence a small depth of field, causing much of the scene to be out of focus. To overcome this, it is useful to select scenes that have only a rather shallow three-dimensional depth.

Going to the other extreme and using a very slow shutter speed to blur moving water creates a very different kind of image. Of course, the measure of 'slow' depends on how fast the water is moving, but in a waterfall or shoreline surf, I’d usually say about 1/10^th second or slower, and—in low light levels especially—sometimes reaching up to 20 or 30 seconds. Clearly, such slow shutter speeds will blur the water, turning it into a rather dreamy silken flowing sheet. However, different shutter speeds will result in rather different effects, creating moods that range from quite restless through to very serene, ethereal and peaceful.

Inevitably, not only will a slow shutter speed make it essential that the camera is mounted on a tripod, but it’ll also result in a very narrow lens aperture and hence a big depth of field—ideal for most forms of landscape photography.

 

Pulling it all together

As this article illustrates, correct exposure of your images relies on a balance between lens aperture and shutter speed, and a thoughtful use of this balance contributes hugely to the creativity of your photography—provided you put yourself in charge of the photography, not the camera!

There are many variables to consider when putting together an image, especially thinking about the shutter speed needed versus the depth of field and the effects you want to create around movement. Get practising, trying out various combinations and styles, and you'll be surprised how creative your photography can become!

 

This blog was written by Nigel Hicks, a hugely experienced Devon-based professional photographer. Nigel works with the USA's prestigious National Geographic Image Collection, among many other bodies, and is a Fellow of the British Institute of Professional Photography.

Nigel Hicks runs regular photography workshops in southwest England. To find out more about these go to www.nigelhicks.com/photography-workshops-courses/.

To find out more about Nigel's work, feel free to take a tour of the website at www.nigelhicks.com.

 

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