The Basics of Exposure 3 – Shutter Speed

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[This is the third article in a series on Basics of Exposure. Before reading this one you should have read, or at least have looked at, Basics of Exposure 1 – Overview and Basics of Exposure 2 – Aperture as these build one on the other.]

Well, if you have sweated your way through the earlier two articles in this series, you will already have learned quite a bit about shutter speed. It’s not possible to talk about exposure and aperture without mentioning shutter speed in the same sentence. They are inseparable.

However, shutter speed, while being intertwined with aperture and ISO setting in the subject of exposure, has a very individual role to play, and contributes in its own way to the finished photograph and the messages you wish to express in your own photography. I will at least begin to cover the subject in this article.

The Shutter and its Speed

The shutter is a precision device that sits between the lens and the light sensor or film (in some cases it is inside the lens itself) which opens and closes to let a timed amount of light in to the camera to create the image. It is not only highly precise, it is also capable of allowing very, very brief bursts of light into the camera.

I just had a look at my Canon EOS 5D Mark II high end prosumer DSLR and it has a shutter which can give an accurately timed exposure from 30 seconds to 1/8000 of a second. I look at my wife’s Nikon D300 which has the same range of shutter speeds. The mind boggles! But even my little Canon Powershot G9 fixed lens mid-range point-and-shoot has shutter speeds from 15 seconds to 1/1800^th of a second. And these cameras, as do most, also have a “Bulb” or “B” setting which lets you keep the shutter open while you time your exposure and then shut it when you think you’ve left it open long enough.

How do they do it? Well, in most cameras of this type you have what is called a “focal plane shutter” which consists of two curtains which move across the sensor independently. Both the speed of travel and the interval between the first curtain traveling across and the second one following it can be controlled. The first curtain starts across and, depending on how long the exposure is, the second curtain follows behind it after a certain time. If they are very close together then only a tiny slit of light is allowed to reach the sensor and it moves quite quickly. The result is a fleeting exposure to each part of the sensor allowing for very fast shutter speeds. When the shutter speed is slow enough, the first curtain is allowed to go all the way across before the second curtain starts its passage so that the entire sensor is exposed for a time before the second curtain comes across and closes it off. So that’s how you can achieve these remarkably fast shutter speeds. 1/8000^th of a second!! There isn’t much motion that that shutter speed can’t stop dead.

Like with the aperture and ISO setting you have three basic modes of operation (most cameras do anyway):

1. Fully automatic – the camera sets everything based on the existing lighting conditions. You point, shoot and hope. Often the result is what you are looking for.

2. Aperture priority Av) or shutter priority (Tv), which is semi-automatic. You set either the aperture or the shutter speed manually and the camera sets the other one automatically to match and get a correct exposure (you hope).

3. Fully manual. You set everything yourself. You choose the ISO setting, the aperture and the shutter speed. You can be assisted in your choice by the light meter built into your camera.

297 shutter image

It’s worth a little note at this point. One of the beauties of digital cameras is that a second or two after you take a photo, you can immediately see what you took. This we take for granted. But with film you are not so lucky. You take the photo and move on. Maybe a day or a week or more later you finish the roll of film and take it to be processed. Back come your prints or your slides and only then do you get to see how you did. By then it is usually too late to take it again. This factor alone of being able to see the shot as soon as you take it makes this a golden age for photographers.

But I digress. Let’s have a look at why you would have different shutter speeds and how you can use them.

NIKON Prime Lenses	CANON Prime Lenses	SIGMA Prime Lenses
Nikon 24mm f/1.4	Canon EF 24mm f/1.4L II	Sigma 24mm f/1.8 EX DG
Nikon AF-S 50mm f/1.4G	Canon EF 50mm f/1.4 USM	Sigma 35mm F1.4 DG HSM
Nikon 35mm f/1.4G	Canon EF 35mm f/1.4L	Sigma 50mm f/1.4 EX DG HSM
Nikon 85mm f/1.4G	Canon EF 85mm f1.2L II	Sigma 85mm f/1.4 EX DG HSM
Nikon 300mm f/2.8G AF-S ED	Canon EF 300mm f/2.8L IS	Sigma 300mm f/2.8 EX DG IF

How to Use Shutter Speeds

The basic purpose of the shutter with its different speeds is to enable you to get correct exposures under different lighting conditions. In accomplishing this, the shutter speed is inextricably intertwined with the aperture and the ISO setting (or film speed of course).

If you have a very brightly lit scene and you use a high ISO setting (maybe 1000) and a wide aperture (perhaps f2) you will have to set your shutter speed very high (maybe even as high as 1/8000^th of a second) to prevent your photo from being way overexposed (which, if you remember, means it will be too light, washed out, pale and thin). Your camera may not have a fast enough shutter speed to give you a correct exposure at all. If you tried to take the photo at 1/30^th or 1/60^th you would have nothing at all to show for it – just a white sheet on your display.

Well, why doesn’t the camera just shoot everything at let’s say 1/60^th of a second and you simply adjust the aperture and the ISO setting to match? One reason is that under bright light conditions it means you will have to use a very narrow aperture (f16 or f22) and that gives you no control over the depth of field. What if you want a shallow depth of field? You cannot attain it in bright light unless you also have a low ISO setting and a fast shutter speed. If you do, then you can use a wide enough aperture to give you shallow depth of field.

And at the other extreme, if you try to shoot in very low light at 1/60^th you will have to raise your ISO setting to shoot even at your widest aperture. And then you lose image quality. So you need to be able to shoot slower under low light conditions.

Being able to select from a whole range of shutter speeds, together with the different aperture and ISO settings, gives you the flexibility you need in order to take great photos in all light conditions.

So there you have the simple exposure considerations associated with shutter speed. It is a tool which helps you, along with ISO setting and aperture, to achieve a satisfactory exposure.

But, just as aperture has an entirely different function than mere achievement of correct exposure (the function of controlling depth of field) so does shutter speed have its separate uses.

Shutter Speed, Motion and Time

It’s quite something that you can show motion quite clearly and dramatically in a single moment of time captured on film or in pixels. A single image, still, can show speed and movement, and can do so quite effectively and dramatically.


Two very different approaches to showing motion. The first one freezes it, the second lets it blur. The Blue Angels are traveling at the same speed in each shot.

It is really the shutter speed that lets you do this, along with some other techniques. The shutter speed lets you capture motion that is too fast for the eye to follow: it can still the vibrating wings of a hummingbird, freeze the lightning fast serve of the tennis champion, stop the racing car in full flight and so on. To do this you need a very fast shutter speed or at least a very short time of exposure. (There is another way to stop very fast motion but we will cover that when we get into the use of electronic flash.)

But freezing very fast motion is only one approach. You can also show motion very effectively by using a slow shutter speed and letting the subject move during the exposure, even to the point of just leaving streaks of light to show that it went by pretty quickly. You’ve seen photos of waterfalls where the water is not still but is just a blurred flow. This can give a better idea of how one perceives a waterfall than a perfectly sharp photo with every drop of water perfectly still and sharp.

There is another application of this technique, most useful at night with fireworks or lightning or the headlights of moving traffic. Here you point your camera at the motion (with a fireworks display or with lightning you have to guess where the action is going to be). Here you’re definitely wise to use a tripod or some other means of keeping the camera absolutely still during a long exposure. Set the camera to Bulb (B) and guess the aperture (you can always start at f8 or f5.6 and see how the first shot comes out and adjust the aperture up or down depending on the exposure you get. Remember, if it’s too dark, then you need a wider aperture – too light, the opposite). When you expect the fireworks or the lightning, open the shutter and keep it open. When the fireworks have done their thing or the lightning has flashed, take your finger off the release and let the shutter close. Have a look at your results. You should have long streaks or forks of lightning. If too bright, use a smaller aperture and try again. If too dark, open the aperture up wider and repeat the procedure.

Fireworks leave their streaks while the shutter is simply left open for long enough for them to record the motion of the light.

Another method, quite popular because it is effective, is to pan with the subject at a relatively slow shutter speed. If you follow the subject faithfully with your camera as it goes by you, left to right, right to left or even up and down, and shoot at perhaps 1/15^th of second or 1/30^th of a second, depending on how fast the subject is moving and the effect you want to create, the resulting photo will show the subject sharp against a blurred, streaky background. This creates the sensation of rapid motion.

There are several motions here, but the panning has caused the background to streak while the subject is relatively unmoving.

Now in these situations, you must understand the basics of exposure in order to get a good shot. Let’s take the panned shot. Well, you can experiment with this. Let’s say you are at a car race. The race cars are flying by. You are looking at the cars with the grandstands and crowds in the background. You need to know how to shoot in Shutter Priority (usually abbreviated Tv which stands for Time value) and/or manual mode. If you don’t know how to do this, you will find it clearly explained in the manual that comes with your camera.

OK. We’ll assume you read that part of the manual. Set the shooting mode to Tv, and the shutter speed to 1/15^th to begin with. You probably want to set your camera to manual focus and pre-focus on a spot in front of you where you expect the car to go. We’ll cover manual focus and tricks of this kind in a separate article. If you don’t understand this, then skip it for now and leave your camera on autofocus. Follow a car in your viewfinder as it comes down the track towards you and, move the camera with it. When it is opposite you, gently squeeze the shutter release and keep following through even after you’ve clicked. You have to follow through – don’t click and stop. Look at the shot. The car should be fairly sharp in the picture. The background, the fence, the faces the grandstand should be all streaked and blurred. If they are not streaked enough, try again, this time at 1/8^th of a second. If they are too streaky and you’ve lost them completely, try again at 1/30^th of a second. Keep varying it till you get the effect you want.


Both these photos show zooming at a relatively slow shutter speed.

If you don’t know how to take your camera off full automatic, you will never get this kind of shot. The camera will faithfully do its best to stop all the motion and even if you pan, you won’t get the effect you are looking for.

A variation of this is to zoom during an exposure. This can be quite interesting (although it can also be overused – you should use these techniques with a purpose, not just as a gimmick).

Here again, you need a slow shutter speed so, in order to get a correct exposure, you will have to have the camera on Shutter Priority (Tv) or on full manual. Maybe even 1/4 or 1/2 a second, A tripod is helpful but not vital. Practice zooming in or out while keeping your subject in the frame and not moving the camera up and down or side to side. Start zooming and then, while you continue to zoom, squeeze the shutter release and keep zooming until after you hear the shutter close. Check your shot in your LCD. If you want more or less motion, adjust the shutter speed accordingly.

Some photographers have developed styles of their own where they deliberately jiggle or move the camera at a fairly slow shutter speed to create a special kind of motion. This is not new. It was made famous by Ernst Haas who was an early mid 20^th century pioneer with color and with techniques to show motion. His studies of bullfights and rodeos are dramatic and unique.

This photo was taken by moving the camera while shooting at a slow shutter speed (photo © Georgianna Lane, www.gardenphotoworld.com)

Summary

I hope I have convinced you that you need to get a good grasp of these basics, learn to take your camera off fully automatic mode, understand the basics of exposure and use your shutter speeds creatively. There is more on the subject and this will be covered in future articles. But let’s get these basics down well. Go back over the first three articles and make sure you have a good, general understanding of exposure and also how to use aperture and shutter speed settings creatively to get photos that are expressive and beautiful. We will go into the actual practical side of it in upcoming articles. But make sure you have at least a basic understanding of the theory.

David © Phillips is a professional writer and photographer living in Seattle, WA. You can find out more about him and his work at www.dcpcom.com

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