Understanding Technical Concepts

Exposure Controls
To get the correct exposure for your photos, you need to know the settings that you can adjust and what they do. Three camera components affect exposure:

Aperture size (represented by f-numbers) can be adjusted to control how much light enters through the lens.

Smaller values such as f/2.8–6.3 mean that your lens is open wide, letting in more light.  This is perfect for shots in low-light situations.

Larger f-stop numbers, such as f/18–36, create a smaller aperture, thus letting in less light at the same shutter speed. These settings are good for landscape shots on a sunny day.

Aperture affects depth of field, which is the range of distance in the picture that is in sharp focus. With a large aperture, the subject is in focus, while areas behind (and in front of) the subject are softly blurred.

Shutter speed refers to how long the shutter remains open. Shutter speeds are commonly marked in fractions of a second.

The slower the shutter speed, the more light is allowed in the camera. Shutter speed determines whether a moving subject appears frozen in time or blurred.

When the shutter is open too long and too much light enters the camera, the image is overexposed and looks pale and washed out. When the shutter isn’t open long enough and not enough light enters the camera, the image is underexposed and appears too dark.

ISO settings determine how sensitive your camera is to light. The higher the ISO number, the greater the light sensitivity and the less light is required to expose the image.

A low ISO setting (50–200) generally produces better images, but the pictures can be dark if not shot in bright sunlight or with a good flash. When shooting at a low ISO setting, you must use a wide aperture and slower shutter speed. That means that you lose depth of field and increase chances of blur.

Higher ISO settings (400–1600) can produce better exposed pictures in low light but also introduce more noise, which can make your image look grainy.

For best picture quality, leave the ISO at its lowest setting. Raise the value only if you’re working in low lighting or trying to capture very fast action.

Exposure Modes
Advanced cameras offer you the option of working in manual mode or in semiautomatic autoexposure (AE) mode.

Manual mode lets you control both the aperture and the shutter speed, giving you nearly complete control over your exposure.

Semiautomatic modes are called aperture-priority and shutter-priority autoexposure. In these modes, you set one control (aperture or shutter speed) and the camera selects the other.

Aperture-priority AE chooses the shutter speed automatically after you set the aperture.

This is an exposure mode that lets you control the time that the shutter of your camera remains open, while your camera automatically sets how wide the aperture opens to let just enough light in to give you a good picture.

Shutter-priority AE sets the aperture automatically based on your selected shutter speed. This exposure mode lets you control the size of the aperture in your lens, while your camera automatically sets how long the shutter remains open to give your picture an adequate exposure.

When you use any autoexposure camera, you must first press the shutter button halfway down until the camera sounds a beep or displays a light near the viewfinder. Then press the button the rest of the way down to capture the image.

Most digital cameras offer an EV compensation control, which slightly increases or decreases the exposure that the autoexposure mechanism deems appropriate.

Metering Modes
Metering is when your camera measures how much light is available in a portion of the frame of your picture. The metering mode determines the area within the frame that’s considered when the camera analyzes the scene and sets the exposure.

Standard options include the following:

Multi-metering measures the light at multiple locations throughout the frame and tries to choose a setting that correctly exposes everything.

Spot metering sets exposure according to the object in the center of the frame.

Center-weighted metering also gives preference to the center of the frame, but doesn’t completely disregard the perimeter.

For routine shots, it’s best to use multi-metering mode. However, if you’re shooting a subject in strong backlighting, multi-metering will “see” all that bright light in the background and use an exposure that leaves your subject too dark. To remedy the problem, switch to center-weighted or spot-metering.

Flash Modes
The correct flash mode varies depending on your subject, lighting, and the type of photography you want to do.

Auto flash triggers the flash when the camera thinks it’s needed, which is a great feature for casual snapshooting.

Fill (or Force) flash fires the flash for every shot. You often need to use this mode for good outdoor portraits.

No flash prevents the flash from firing, which is a good thing when you’re trying to shoot shiny objects, such as glass or chrome.

Red-eye flash produces a small flash that lights in advance of the main flash. This reduces the chance of red-eye.

Slow-sync flash enables you to use slower shutter speeds than the camera normally allows for flash photography. When you’re shooting at night or in a dimly lit room, this mode enables you to capture both subject and background. Without it, the background usually appears dark.

Focus Modes
With most digital cameras you get both a macro focusing option for shooting close-ups and a standard focusing setting for normal photography.

In autofocus modes, the camera sets the focus automatically when you press the shutter button halfway down. If you don’t want your main subject to be centered in the picture, frame the image with the subject in the center, press and hold the shutter button halfway down to “lock” the focus distance, reframe the scene, and then press the shutter button the rest of the way down.

White Balance
Digital cameras usually have both automatic and manual white balance settings, which may include Daylight, Shade (or Cloudy), Fluorescent, and Incandescent (or Tungsten). Since different light sources have different hues, white balance enables the camera to compensate for any colour cast that may be created by the light source.

Generally speaking, you can leave your camera set to Auto, but there may be times that you want to use an incorrect white balance setting for special effects such as those you get from a warming or cooling filter.

Creative Scene Modes
Most digital cameras offer some preset shooting modes. Typically, you can select from at least two modes: portrait and landscape. Some cameras go further and offer an action mode for capturing moving subjects and night-time mode.

The following list describes the scene modes available on most digital cameras:

Auto - Use this mode in places with good lighting, sun or shade, during the daylight hours and in shots with little or no action.

Portrait - This mode is perfect when you want a clear shot of your subject’s face up close. Soften the look of animals by shooting them up close in portrait mode.

Landscape - When you’re shooting to the horizon, with lots of distance to cover and you want it all to come out sharp, use the landscape mode.

Close-up or macro - Use the macro mode for those times when you want one or two objects in focus and everything else in the background/foreground blurred.

Action - This mode uses higher shutter speeds to stop action with little or no blur.

Night - This mode will come in handy when you’re photographing a scene at night without a flash. Remember to keep the camera very still to avoid a blurry photo — this mode generally uses a slower shutter speed.