Digital cameras offer photographers great control Nathan Weiss
At some point, proper exposure should be a given and not a goal. Taking the
next step as a photographer means it’s time to exert more control over the
image-making process. After you determine the necessary settings for correct
exposure, the next thing to consider is how to manipulate those settings to
achieve your photographic vision. Digital cameras offer photographers great
control over the image-making process. Not only can you shift shutter speed
and aperture controls as needed, but you can also change ISO settings from
image to image. If a shot requires greater depth of field than conditions
allow, you can dial up a higher ISO setting and gain an extra f-stop or two.
If there’s too much depth of field for a desired effect, dial down your ISO
setting and lose an f-stop or two. You should always have some understanding
of why you’re using a certain aperture or shutter speed combination. It can be
as vague as making sure you have a fast enough shutter speed to stop action or
a wide enough aperture to throw the background out of focus, but you should
still exercise some logic when choosing your settings.
Many people think that photography documents reality; but in truth, it only captures incredibly brief moments. How many tasks do you perform in your everyday life that can be measured in 1/30 of a second? Yet 1/30 of a second is considered a slow shutter speed in photographic terms. One of the greatest modern photographers, Henri Cartier Bresson, is best known for expressing the need to capture the decisive moment—the split second when action is at its peak and emotion at its most intense. Part of photography’s challenge is to recognize the exact moment to create a photograph. This article helps you understand shutter speed and your camera’s response so that you can fire off the shot at precisely the right moment. Documenting that magic moment is in part a function of how long your camera’s shutter remains open. Learning to recognize when to favor one extreme over another can lead to dramatic impact in your images.
Before you consider how to use shutter speeds most effectively, you need to know how to make your camera respond to your needs. Modern cameras (both film and digital) have to accomplish an amazing number of tasks before the shutter fires. They need to take light meter readings, make auto-exposure settings, and lock auto-focus in a split second. In addition, digital cameras often add another step. If you’re using a micro-drive as your media (as your “digital film”), you’re working with a miniature computer hard drive. Its micro-drive platters (which receive the image data) need to be spun up to the proper operating speed for recording data. The time necessary for your camera to accomplish all these tasks is known as shutter lag. It’s the reason why nothing happens when you first press the shutter button. Depending on your camera, there are usually some things you can do to compensate for shutter lag. Some cameras allow you to press the shutter button halfway down to activate many of the systems just mentioned. If your camera has this functionality, it’s wise to develop the habit of pressing the shutter button halfway shortly before you anticipate taking a photo. Be mindful that this technique drains your batteries faster, so be prepared with extra batteries. Another way to make your camera more responsive is to pre-focus it. This trick resulted in sharp images long before the advent of auto-focus, and it still increases the odds of getting an in-focus shot—even with the best auto-focus systems.
Pre-focusing works with almost any type of digital camera. Simply focus the camera on the spot where you anticipate the action will happen. Although this technique may not give you the perfect shot every time, at least you give your camera a head start on focusing. This technique helps your camera lock focus faster. These are the kinds of tricks pros use to get the most out of their gear. I’ve certainly relied on them for many of my favorite photos. After you tweak your camera’s responsiveness, you’re ready to concentrate on getting the shot. Perhaps it’s overkill, but most cameras offer a broad range of shutter speeds, from as much as 30 seconds to as fast as thousandths of a second. Who really needs a 10-second exposure, or 1/2000 of a second, for that matter? You do. These extremes make it possible to create images that stand out. Here are some examples of how to use extreme shutter speeds.
Slow shutter speeds:
Moving water: Long exposures give moving water a beautiful spun glass texture. Set your camera up on a tripod or stable surface and rig your camera for a five-second exposure or longer. You can choose your lowest ISO setting and use neutral density filters to block light so you can get to the slow shutter speed. If you’re photographing water in the shade, consider using a warming filter to get rid of some of the excess blue light.
Fireworks: A shutter speed measured in seconds can give your camera’s sensor time to record several good bursts, creating a spectacular image.
Removing cars and people: With long exposures, moving objects aren’t in the scene long enough to register as part of the image. Before Photoshop, photographers used very long exposures to remove people and moving cars from their images.
Ribbons of light: Find a busy roadway and set your camera up on a tripod. Set up for a long exposure and the passing vehicles’ headlights and taillights register in the image as ribbons of colored light.
Fast shutter speeds:
Moving water: Extremely fast shutter speeds can also create interesting effects when shooting moving water. Here the tiny fraction of a second the shutter remains open can freeze individual water droplets into a crystalline spray, or capture a waterfall as it plunges over a cliff.
Freezing motion: Extremely fast shutter speeds stop motion. Often, this doesn’t result in a spectacular image, but you can use fast shutter speeds to your advantage. You can freeze an athlete’s hair flying through the air or freeze a ball in mid-flight as it approaches an athlete.
Choosing a shutter speed that’s fast enough to freeze most of your subject, but still slow enough to blur parts of it (such as hands or feet), is one of the trickiest ways to photograph motion. Still, this kind of shot does much to give a feeling of movement to a photo. Generally, a shutter speed between 1/60 and 1/90 of a second is a good starting point for attempting a blurred extremities image, but it depends on what subject you’re shooting. A variation of the slow shutter-partial frozen action approach is called panning. When shooting a panning shot, you follow your subject with your camera as it moves through a scene. Besides moving your camera, add a slow enough shutter speed (which is dependent on how fast your subject is moving) so the shutter remains open long enough to blur the background. You’ve just created an image in which your subject is sharp and the background is blurred, giving a sense that your subject is moving rapidly. Without knowing specifics of the shot, it’s hard to quantify what shutter speed you should use, but here are some examples to consider:
Jogger: Experiment with shutter speeds ranging from 1/30th to 1/60th of a second.
Cyclist moving quickly: Try 1/30th to 1/125th of a second.
Automobile moving at normal driving speeds: Try 1/30th to 1/125th of a second.
Automobile moving at highway speeds: Try 1/125th to 1/250th of a second.
Automobile racing: Try 1/250th to 1/500th of a second.
This isn’t the kind of photography where you shoot once and figure you’ve nailed it. It takes trial and error and a willingness to waste shots (something that’s easier to do with a digital camera). Take some practice swings first. In other words, practice pivoting the camera and your upper body around as you follow your subject. Remember, you’re going to have to press the shutter button during your pivot, so you want this motion to be as smooth as possible. Accept the fact that you might have to take 30 pictures to get one good one with this technique. It can be worth it because that one good shot will be so different than all the other photos you take. The terms F-stop and aperture are used interchangeably to describe the same thing: how much the lens opens to let light hit the camera’s sensor. This is the second part of the relationship that reads shutter speed + f-stop = exposure. In simple terms, the correct combination of shutter speed and lens opening produces the correct exposure. From a purely technical standpoint, you need a value of X for a proper exposure; if your shutter speed and aperture add up to X, you’ve got a good exposure. Achieving proper exposure is a minimal accomplishment for the creative photographer, particularly with today’s sophisticated digital cameras. The creative part of the process comes when the photographer decides on a certain combination of shutter speed and aperture that achieves proper exposure and also takes advantage of the nuances the two controls offer. Shutter speeds offer the ability to freeze or blur motion, and f-stops offer the ability to control depth of field. Depth of field is an issue that many novice photographers have trouble grasping. Even though the photograph is a two-dimensional image, the scene depicted within it represents a three-dimensional world. The apparent distance from foreground to background is the image’s depth of field. The range of apparent sharpness from foreground to background is determined by the size of the lens opening (the aperture or f-stop). Use a large lens opening, and the range of sharpness is minimal. This is described as “shallow depth of field” because only a small range of foreground to background area will be sharply focused. Use a small lens opening, and the range of apparent sharpness will be much greater.
Keeping the entire image area sharp from foreground to background depends entirely on your choice of aperture setting. The smaller the lens opening, the sharper the photograph’s focus is from foreground to background. Aperture sizes are determined by dividing the focal length of the lens by a particular lens opening. As the lens openings get smaller, the f-stop number increases, hence larger f-stop numbers translate to smaller lens openings. For example, most high-end lenses offer great light-gathering capabilities. These lenses frequently offer a maximum lens opening of f2.8. As you close down the size of the lens opening (an action referred to as “stopping down”) the lens opening gets smaller, whereas its f-stop designation gets larger. A normal sequence goes f2.8, f4, f5.6, f8, f11, f16, f22. Math aficionados will likely recognize this as a logarithmic progression. Understanding that a larger lens opening results in a shallower depth of field, and a smaller lens opening provides greater depth of field, provides the photographer with a useful set of tools for creative control. If you want the entire scene sharp from foreground to background, choose a small lens opening (large f-stop number, such as f11 or f16). If you’re trying to photograph a subject within a cluttered scene and want to isolate your subject from everything else, go with a large lens opening and focus precisely on your subject to throw the background out of focus. There are a couple of focusing options that you can use, zone and selective focusing.