15 seconds at f/11 created this fanciful image where regular party-goers are transformed into smokey ghosts.

Any camera equipped with automatic or program mode is capable of making a proper exposure on its own, but choosing an exposure is about more than letting in the right amount of light.  If you let your camera decide how the correct exposure balance is achieved, you miss out on a lot of creative opportunities.  In Elements of Exposure – Part 1: Aperture, we discussed how changing the size of the aperture controls depth of field in our images.  In this article, we will discuss how adjusting the shutter speed can be used to show or stop motion.

1. How Shutters Work

The shutter is located inside the camera, in front of the recording medium (for example, the film or digital sensor). The shutter remains sealed most of the time, preventing any light from reaching the recording medium until you’re ready to take a picture. When you press the shutter release button, the shutter opens like a sliding glass door and allows the light to enter the camera and record your photograph.  After it has stayed open for the specified amount

Image of Ferris Wheel taken at 1/40 of a second (shutter speed: 40)

of time, the shutter closes to prevent any additional light from entering.  If you are using Program mode or Aperture Priority mode, your camera will decide how long the shutter stays open.  Sometimes the camera’s choice may be acceptable, but if you want to try a special technique or  control how much motion is shown in your photograph, you can take control of your shutter by using Manual mode or Shutter Priority mode.   With Manual mode, you will have to set both the aperture size and the shutter speed yourself.  With Shutter Priority mode, you can set the shutter speed yourself, but the camera will calculate the aperture size for you.  The steps for selecting a specific shutter speed vary from camera to camera, so you should consult your owners manual for specific instructions.  All cameras express shutter speeds in seconds and fractions of seconds.  For example, a shutter speed of 250 will open the shutter for 1/250 of a second.  A shutter speed of 2” will open the shutter for 2 seconds.  It follows then that a shutter speed of 8000 will be open for a much shorter time and let in far less light than a shutter speed of 250, which might be confusing at first.

2. Motion

Ferris Wheel image taken with a 2 second exposure

When deciding on a shutter speed, you should consider how much motion you want to include in your image.  Do you want to stop (freeze) the motion, or do you want to show motion?  There are times when you want to stop motion to freeze a critical moment.  For example, if you’re photographing a basketball game, you might want to freeze the action to create a crisp image of a player dunking the ball.  Other times you might want to intentionally include an element of motion in your images.  Motion can really enhance some photographs, such as those of running water, smoke patterns, and race cars. Motion can also be added to an image to convey a feeling of chaos or busyness, or of time passing.  If you do decide to include motion in your image, you then need to ask yourself how much motion you want to show.  It will take some practice to learn which shutter speeds to use.  One of the big advantage of digital cameras is you can try the image with one shutter speed, view it on the preview screen, then make any necessary adjustments before taking another photograph.

A fast shutter speed of 1250 freezes the water droplets mid-air in this fountain image.

There are two types of motion that can be introduced into your photograph when you use a slow shutter speed.  There’s the camera’s motion (i.e. camera shake), and the subject’s motion.  Most of the time in photography, camera shake is not desirable.  There can be some instances when the artist decides to allow camera shake in an image for an effect, but almost all the time we try to eliminate camera shake from our images.  People vary in their capabilities to hold things steady, so do some tests with your camera to see how slow a shutter speed you can use without introducing camera shake.  The general rule of thumb is to use a tripod for shutter speeds slower than the focal length of your lens.  Think of it in terms of this example.  If you have a 50mm fixed focal length lens mounted to your camera, you’ll want to use a tripod for any shutter speed slower than 1/50 of a second.  Most cameras don’t have a shutter speed setting of 50, so 30 may be your next closest shutter speed.  Everyone’s different though, and I find that I’m able to hand-hold the camera at 1/30 of a second without shake.  If your lens has vibration reduction or image stabilization, you should be able to hand-hold the camera at even slower shutter speeds.  Although camera shake is normally considered undesirable in a photograph, there are other types of camera movement that are sometimes used to produce very

In this image of the same fountain, I slowed my shutter to 1/25 of a second which gave the water a more fluid, silky look.

interesting images, such as panning and zoom burst, which move the camera or the lens in a precisely controlled motion to create a specific effect.

Usually when we talk about adding motion to an image, we are referring to the subject’s motion.  Long exposures can bring mist and fluidity to photographs of rivers and waterfalls.  A picture of a dancer can become more interesting when it shows her moving through the air, rather than frozen crisply in an unnatural position.  There are hundreds of applications for slow shutter photography.  One of my personal favorite applications for long exposures is street scenes, because I love the busy feeling given by all the cars whirring by.  For shots like this when we want to emphasize the motion of one particular subject in the photograph, it’s important to use a tripod so that the subject’s motion is prominently displayed in the image and the viewer is not distracted by camera shake motion.

3. Compensating for Shutter Speed
We’ve all heard our elders telling us that life is full of compromise, and unfortunately, so is photography.  When you change the shutter speed, you have to decide what else to change.  You have four choices:

1. You can change the ISO
2. You can change the aperture (F-stop)
3. You can change the filter
4. You can change the scene

This image posed an interesting challenge. The lighting was very dim, but I wanted to use a fast shutter speed to freeze these dancers in mid-air. To compensate, I increased my camera's ISO setting to 4,000 and used my lens' widest aperture, f/2.8. This allowed me to use a relatively fast shutter speed, 1/250 of a second (250), which was just barely fast enough to stop the motion in this image.

I will be covering ISO in more detail in another article, but here are the basics:  a higher ISO number allows in more light, and introduces more grain into the image.  That means if you have chosen a fast shutter speed, you might need to increase the ISO to get the proper exposure.  If you have chosen a slow shutter speed, you will probably be able to use a slower ISO and have a cleaner, less grainy image.  Another option is to leave your ISO alone and make changes to the aperture.  The aperture controls your depth of field (that is to say, it controls how much of your picture will be in focus).  If you can’t get the image you want by adjusting any of the on-camera controls, sometimes you have the option of adding (or removing) a filter to get the image you want.

As you can probably tell by the lighting, this image was taken in bright mid-day sun. Normally, an image like this would require a very fast shutter speed, even when using a small sized aperture. I was able to slow the motion in the water while keeping the shallow depth of field I wanted by using a neutral density filter. The shutter speed in this image is 1/10 of a second.

For example, if you have decided you want to make a long exposure with shallow depth of field (large aperture diameter/ small f-stop number) on a bright sunny day, you may not be able to adjust your ISO low enough to give you the exposure you want.  In this case you can attach a Neutral Density filter to your lens to block out some of the light.  In some cases, a circular polarizer filter can be used for a similar effect.   The advantage to using a circular polarizer is that it blocks out reflections from water and other shiny surfaces in addition to blocking 1-2 stops of light, which can be desirable in some circumstances.  If none of these options are satisfactory, sometimes it’s possible to modify the scene.  You can bring in lamps, strobes, or reflectors to add more light into your scene, or you can use opaque objects to block some of the light from entering your image.  It should also be said that you don’t have to choose just one of these options, often the ideal solution is found by tweaking two or more of the four variables listed.

4. Controlling Shutter Speed on the camera

I wanted to show the entire trail of the firework in this image, not just the burst at the end. To include that motion, I slowed my shutter to 8 seconds. Even though the lighting was dim, to get a correct exposure with an 8 second shutter speed, I had to increase my aperture to f/13, which was fine in this case because I wanted enough depth of field to show the firework and the monument in crisp focus.

Camera functions vary depending on the make and model of the camera, but most cameras give you two options to control your shutter speed.  You can put your camera in Shutter Priority Mode, which allows you to manually set the shutter speed and allow the camera to choose the aperture for you.  The advantage of this mode is it allows you to move quickly from scene to scene without much thought to the exposure.  Most of the time you will get a decent exposure with this method, but it may not be exactly what you wanted.  The camera may also choose a depth of field that is not flattering to the photograph, and not in harmony with your vision for the image.  The other option the camera gives you is Manual mode.  In this mode you will have to manually set both the shutter speed and the aperture yourself.  Personally, I choose never to operate in shutter priority mode.  In my opinion, the aperture has much to important an impact on the final image to give that control over to the camera.  I sometimes use Aperture priority mode, but if I want to have a say over the shutter speed in my image I switch over to Manual.  I have found that with practice, Manual mode can actually be faster and easier to use than the program modes.

This image is a composite of about 5 different exposures, each with a shutter speed of one second.