Contents
Digital Camera Basics
How Digital Cameras Work
Types of Digital Cameras
How to Choose a Digital Camera
Popular Digital Camera Models
How to Test-Drive Your Digital Camera
Digital Camera Operating Modes
Digital Camera Accessories
Digital Camera Software
How to Care for a Digital Camera
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How Digital Cameras Work
If you want to make an informed decision about which type of digital camera suits you best, it helps to know how digital cameras operate.
Image Sensor
Digital cameras capture light on an image sensor made up of electrodes, called photo-sites. Each photo-site contains one pixel, a tiny electronic block of color. The photos that digital cameras produce are composed of millions of pixels that form an image when viewed together, much as a TV produces images from tiny red, green, and blue dots.
Image Resolution
A digital photo’s resolution is the number of pixels it contains. Each digital photo has a specific resolution based on:
- The number of photo-sites on its sensor: The more sites, the higher the resolution your shots can be.
- The quality setting you’ve selected: Digital cameras have various quality settings, such as “low/medium/high” or “normal/fine/superfine,” that allow you to determine the resolution of your shots. Higher-resolution settings produce clearer photos that print more sharply than lower-resolution photos but use more memory.
The resolution of a digital photo is expressed in:
- Pixel dimensions: This is the actual number of pixels that make up the width and height of the photo (an 800×600 photo is 800 pixels wide and 600 pixels high).
- Pixel count: The total number of pixels the photo contains. A 1000×1000 photo contains 1,000,000 pixels, called a megapixel. Cameras are typically described according to the number of megapixels they capture at their highest-resolution setting (for example, a 4-megapixel camera can shoot photos that contain 4 million pixels).
White Balance
The specific type of light present when photos are taken impacts the way colors are recorded on the camera’s sensor. Types of light include sunshine, fluorescent light, and tungsten (standard lightbulb) light.
White balance is a term used to describe the accuracy of the colors that appear in a photo. When white balance is set correctly, the color white looks white instead of off-white, yellow, or gray, and this balance is reflected in the photos you take. Once white balance is achieved, all other colors will display properly. Digital cameras typically include a white-balance feature that allows you to specify the type of light in which you want to take your photos.
Exposure
Like film cameras, digital cameras use an aperture and shutter to control each image’s exposure, or the amount of light that passes through the lens to record the image onto the sensor.
Shutter
A digital camera’s shutter is like a tiny curtain that covers the sensor. (Note that the word “shutter” is also used to refer to the shutter button, the button you press to take photos.) The shutter is normally closed, but opens when you push the button to take a picture, exposing the image sensor to light. The time during which the sensor is exposed to light is called the exposure time.
You can set the shutter on a camera to open for a specfiic amount of time, called the shutter speed. Shutter speed is usually a fraction of a second (a shutter speed of 1/125 will open the shutter for 1/125th of a second).
- The slower the shutter speed: The longer the exposure time, and the more light enters the camera
- The faster the shutter speed: The shorter the exposure time, and the less light enters the camera
How the Shutter Speed Affects Your Photos
Photographers vary the shutter speed based on the conditions of the light in a scene and the motion of the subject.
- Use slower shutter speeds: When you’re photographing still objects or objects in very low light
- Use faster shutter speeds: To freeze the motion when you’re photographing objects in motion, such as athletes running, or when photographing objects in bright light (using slow shutter speeds on moving subjects will cause those subjects to blur)
Photographers sometimes break these rules intentionally to achieve desired effects, such as using a long shutter speed to blur the image of a sprinting athlete.
Aperture
The aperture is a small, circular opening inside the lens. It controls the amount of light that passes through the lens and thus the amount of light in your photo. A larger aperture allows more light to enter the camera, whereas a smaller aperture allows less light.
Aperture Settings
Aperture settings are measured in increments called
f-stops, which are written with the letter “f” followed by a slash and a number, such as f/2.8. The standard set of f-stops includes f/2.8 (largest aperture), f/5.6, f/8, f/11, f/16, f/22, and f/32 (smallest aperture). Though high-end digital SLR cameras typically include the complete set of standard apertures, entry-level digital cameras often have fewer total apertures (for more info on the apertures of specific camera models, see Popular Digital Camera Models).
How the Aperture Affects Your Photos
In addition to determining how much light passes through the lens, the aperture controls the photo’s depth of field, or how deep into a scene objects should appear in focus.
- Larger apertures: These have a shallow depth of field, meaning that if you focus on one particular object in a scene, anything closer to or further away from the camera is not in focus. Photographers often use large apertures to focus on an object in the foreground while intentionally blurring the background.
- Smaller apertures: These have a greater depth of field, meaning that objects relatively close to or more distant from the camera are in focus. Photographers use smaller apertures when shooting landscapes in which both the foreground and background should be in focus.
How the Shutter and Aperture Work Together
When you select the right shutter speed and aperture size, your photos appear properly exposed, meaning the scenes look much like they do to your naked eye. With the wrong settings, photos can look underexposed or overexposed.
- Underexposure: Occurs when the shutter and aperture don’t let in enough light, making photos dark
- Overexposure: Occurs when the shutter and aperture let in too much light, making photos look washed out
Light Meters
Most digital cameras have a built-in light meter, an indicator that measures light and suggests which combination of
aperture and shutter speed to use for each photo you take. As you shoot, you can allow the light meter to set the shutter speed and aperture size automatically, or you can override the light meter’s recommended settings.
For instance, if the light meter recommends a large aperture but you’d like to capture the entire scene in focus, you might override the light meter by selecting a small aperture. In that case, the camera will reduce the shutter speed proportionately to allow the light required for proper exposure to reach the sensor (for more on how to choose these settings, see Digital Camera Operating Modes).
ISO
Digital cameras use the same rating system, known as ISO, to describe the light sensitivity of the image sensor that film cameras use to describe film’s light sensitivity. ISO is
measured in numbers ranging from 50 (the lowest sensitivity) to 3200 (the highest), though most entry level digital cameras only have ISO settings from 100–1000.
- Use low ISO settings: When ample light is present, such as on sunny days or in brightly lit rooms
- Use high ISO settings: When little light is present, such as when photographing at night
How the ISO Setting Affects Your Photos
Photos shot at high ISO speeds appear grainier, or “noisier,” than those shot at low ISO speeds. Since you can switch ISO with every shot you take on digital cameras—as opposed to having to shoot an entire roll of film at the same ISO—try shooting the same scene at several ISOs and choose the least grainy shot when editing your photos onscreen later.
Photo Storage
The memory cards on which digital cameras store photos come in four main varieties: Memory Stick®, xD-Picture Card®, Secure Digital (SD)®, and CompactFlash (CF)®. All four formats work roughly the same way—like tiny hard drives, they store your photos as separate files while you shoot. When you buy your camera you'll likely have to buy a memory card as well, but be sure to buy the specific type of memory card that your camera takes.
Digital Photo File Formats
Digital cameras save photos in two main formats: JPEG and RAW. Choose a format based on the type of camera you have, your level of experience, and your image editing needs. Most entry-level cameras store photos only as JPEGs, which should suffice for basic everyday use.
View, Edit, and Print Photos
To view, edit, email, or print your photos, you must first download, or transfer, them from the memory card to your computer. To do this, either connect the camera itself to the computer (with a cable that comes with your camera), or use a card reader (see Digital Camera Accessories). Once you’ve transferred photos to your computer, you can view, edit, and print them using image editing software, such as Adobe Photoshop (see Digital Camera Software).
Lenses
All camera lenses are either fixed or zoom. Fixed, or prime, lenses have one fixed focal length. Focal length, measured in millimeters, determines the lens’s field of view, the
portion of the scene before you that the lens lets you see and photograph. Fixed lenses have one focal length measurement, such as 40mm, while zoom lenses have a variable focal length, such as 40–200mm.
- Higher focal lengths: Zoom in on, or magnify, subjects in the field of view so you can capture them as they would appear if you were closer up
- Lower focal lengths: Widen the field of view, allowing you to capture more of the scene
Nearly all entry-level digital cameras have zoom lenses—
many with broad focal length ranges, such as 30–300mm. Most digital cameras offer two kinds of zoom:
- Optical zoom: This varies the focal length of the lens when you press a lever or turn the lens itself. Optical zoom allows you to zoom in or out on a scene without compromising image quality.
- Digital zoom: This artificial effect creates the appearance of zooming in even further than the optical zoom, but with a noticeable loss of image quality.
The magnification power of optical and digital zooms is expressed as a number followed by an x, such as 10x. A camera with a 10x optical zoom lens can multiply the size of the subject in the field of view 10 times as you zoom in from its minimum to its maximum focal length. When shopping for a digital camera, consider the power of the optical zoom only; you’ll rarely use digital zoom because the image quality it produces is poor.
Focus
All entry-level digital cameras have autofocus lenses, which let the camera focus for you, usually by focusing on the subject in the center of the field of view when you press the shutter button down halfway. Most digital cameras also offer a manual focusing mode, which allows you to select a spot in the field of view on which to focus, and then lets you fine-tune the actual focusing. Manual focus is useful when focusing on objects that aren’t in the center of the field of view.
LCD
The LCD (liquid crystal display) is a small screen that lets you preview and review images as you shoot them. The screen also serves as an interface for some of the camera’s settings, such as image resolution. LCDs are either mounted within the camera’s main body or on a hinge that allows you to flip the screen out and rotate it.
Image Stabilization
The image stabilization feature reduces blur that results when you move while taking a photo. This feature is
especially useful in low-light situations (when the shutter remains open longer than usual to allow light to enter the lens, increasing the chance that you’ll move slightly and blur the photos you take).
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