Shutter Speed
An Overview

The basic function of shutter speed is to control the time during which light hits the film or digital sensor. Very early cameras, like the ones used by the famous photographer Mathew Brady didn't even have a shutter! When he was ready to make a photograph, he simply removed the lens cap by hand and then replaced it after a predetermined length of time.

Photographic plates of that era weren't very sensitive to light and exposures of five or even ten minutes were not uncommon! Have you ever seen photographs of city streets taken in the late 1800's? If so, you'll notice not many included people! This is because the lens cap, or shutter was left open for a very long time and people moving through the image weren't there long enough to be exposed on the plates!

Today, that method of timing exposure during the day wouldn't work. Film and digital sensors are so sensitive that exposure times are measured in fractions of a second. And to photograph objects in motion and render them sharp, exposure times of 1/60 second or faster are required.

Modern cameras use either a mechanical or electronic shutter where precise intervals of a fraction of a second can be selected. Some cameras show the shutter speed on a dial. Others use an LCD readout on a panel and/or in the Viewfinder. Regardless of how your particular camera displays shutter speed, the number 1000 represents 1/1000th-of-a-second.

Types of Shutters

There two principle types of shutter. Between the lens and focal plane. The between the lens shutter, also called a leaf shutter, is made up of a series of thin steel blades. It is usually located in the lens itself, placed between lens elements. Because of design limitations, it's speed is limited to 1/500 second.

The focal plane shutter is located in the camera body, just in front of the film or sensor. It offers two distinct advantages over the leaf shutter. First, because the shutter is located in the camera, not the lens, interchangeable lenses are usually less expensive. Second, the focal plane shutter is capable of much faster speeds.

How the Focal Plane Shutter Works

The focal plane shutter consists of not one but two separate curtains! With the shutter speed set at 1/60 second, when you press the shutter release the first curtain snaps open to start exposure process. After that predetermined time has elapsed, the second curtain snaps shut. This operation is limited to be about 1/125 second in most SLR cameras.

This is slower than the leaf shutter! You just stated above that the focal plane shutter is capable of very high speeds. How can this type of shutter reach these high speeds? It exposes only a part of the film at a time! Here's how! At very fast exposure speeds, instead of the second curtain waiting for the first crtain to fully open, the second curtain starts to follow the first curtain before the frame is fully exposed. The film or digital sensor is exposed by a small "slit" of light between the two curtains as they sweep across the frame.

How does this system allow for extremely fast shutter speeds? Let's say the distance, or "slit" between the first and second curtain as they move across the frame is 1/8 of the frame wide at 1/500 second. To increase the speed of the exposure, we simply make the "slit" smaller! At 1/1000 second, the second curtain starts sooner and the "slit" would only span 1/16 of the frame.

That is how the focal plane shutter achieve such high speeds. Not that the curtains move any faster, but because the film or sensor is exposed by a sliver-thin slit between the two moving curtains. Your understanding of how the focal plane shutter works will help you later to understand flash photography.

Speed and Motion

To get a sharp image of an object in motion like a speeding car, running horse or waterfall, you will need a shutter speed fast enough to "freeze" the action.

But, to make that same waterfall look like smooth, spun cotton candy, a longer exposure will be required, along with the use of a tripod. So what is the right shutter speed? The right shutter speed is the speed that helps you best express your theme. Where YOU get the effect you want!

Your Choice of Shutter Speed
Depends on Four Factors

The direction of the moving object. An object seems to be moving faster when it moves across your field of view then when it is coming at you or moving away.

The distance of the moving object. The closer the subject is to the camera, the larger it will appear in the viewfinder and the larger the subject appears, the faster it moves across the frame. At any given shutter speed, the farther you are from the moving subject, the less blurring will be caused by the motion.

Finally, the focal length of your lens. The longer the lens, the larger the subject will appear in the viewfinder. The larger the subject, the faster it will move across the frame. Using a telephoto lens is just like moving closer to the subject.

Techniques for Showing Speed

You are at a Barrel Racing Event and you want the people who couldn't be there to experience the speed an beauty of the horses and riders! If this is your first attempt at photographing an event like this, I would suggest setting your camera in the Shutter Priority Mode, let the camera choose the Aperture setting for a proper exposure. When you feel more comfortable, you may want to experiment with the Manual Mode for more creative control.

Everyone has seen snapshots of a running horse where not only the horse but the background are "frozen in time". You can see that the horse is running, but the image does nothing to convey the "real" speed of the horse! How do you capture an image that conveying both speed and motion?

By using a slower shutter speed and a technique called Panning. Panning is where you move the camera along with the subject. Use a shutter speed just fast enough to give you a sharp image of the horse and rider. The motion of the camera will blur the background. A little blurring of the legs may also occur but will add to the impression of speed!

Start by positioning yourself about half way between the start and the first barrel. Get as close as safely possible or use a telephoto lens if you have one. Set your shutter speed to 1/60 second. Focus on the horse and rider as they enter the arena. Pan along with them and snap the shutter when they are almost directly in front of you. Do not stop panning after you press the shutter, have a nice smooth follow through.

If your camera allows you take more than one exposure by holding the shutter down, here is a good time to use that function. Take three images in succession. That way you can choose the best image! Don't forget to continue your follow-through!

Check the image(s). Is the subject in sharp focus? If not, you may want to consider using a tripod with a panning head if you have one. Is the background motion-blurred? If the background is not sufficiently blurred, reduce the speed by one stop to 1/30 second or zoom in closer, if you can, and shoot again. Do not be afraid to experiment! If you are satisfied with your images continue to shoot.

Now move to a position close to a barrel. Leave your camera set on Shutter Priority. Set your shutter speed to 1/500 second to freeze the action! Make sure your subject fills the frame and shoot as the horse and rider round the barrel.

Try using these techniques the next time you are out shooting! I'll bet that your images will improve!

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