Specs Explained

Digital Camera Specs Explained :

Although digital cameras are more alike than different, the devil is in the details. What features a particular model offers and how well they are implemented helps determine whether a particular camera is right for you. Not every digital camera will suit every user, nor will every feature make sense for every digital camera. The descriptions here will provide you with the basic information about many of the features you'll find and what they can do, allowing you to decide if you must have a specific feature or can easily live without it.

Image sensor:

	Resolution. The resolution of an image sensor tells you how many discrete points of light, called pixels (short for picture elements) it can capture. The higher the number, the more you can enlarge the image without significant quality loss. Don't be misled into believing that more is necessarily better, since resolution is only one factor affecting overall image quality. When shopping for your digital camera, consider optical resolution only, which is the physical resolution—the actual number of image-sensing elements.
	CCD (charge-coupled device). The most common kind of image sensor for digital cameras. CCDs generally produce higher-quality images than devices based on CMOS, the other common image–sensor technology. CCDs, though, are more difficult to manufacture, require additional circuitry, and generally use more battery power.
	CMOS (complementary metal-oxide semiconductor). Image sensors produced with this technology require less circuitry than CCDs, but image quality is usually not as good. On the other hand, CMOS-based cameras can be as small as your thumbnail. Because CMOS chips are less expensive to manufacture, they are generally found in low-cost, limited-function digital cameras. A handful of prosumer and professional cameras use high-quality CMOS chips, though.
	Light sensitivity. This is a measure of how much light a digital camera needs to take a perfectly exposed picture. Usually, a camera's light sensitivity is stated as its ISO equivalency (light sensitivity expressed in the terms used to rate the same characteristic in film). A low ISO setting (50 to 100) generally produces better, cleaner images, but the pictures can be dark if not shot in bright sunlight or using a good flash. Higher ISO settings (200 to 1,600) can produce better-exposed pictures in low light, but also introduce more electronic noise, which can degrade image quality. All but the least expensive digital cameras offer a range of user-selectable ISO settings. Most inexpensive units have ISO equivalency settings that vary automatically and can't be changed by users.

Lens:

	Speed. Lens "speed" actually refers to the amount of light the lens lets in when its light-restricting diaphragm is completely open. The unit of measurement is the f number or f-stop (the same unit used to describe the size of a lens diaphragm's aperture). A fast lens—an f2 or f2.8—is suitable for shooting in low light but limits the depth of field, throwing the foreground and background out of focus. Very inexpensive, box-type digital cameras have slow lenses with fixed apertures. Many digital cameras feature mechanical diaphragms that can stop down (reduce) the aperture to anywhere from f8 to f11 for producing greater depth of field. (Check out aperture in the glossary for further information.)
	Focal length. The distance between the lens and the image sensor is the focal length of the lens. Modifying a lens to increase its focal length makes objects appear magnified and closer. Decreasing focal length makes things appear further away but widens your field of view. Most digital cameras have small lenses with tiny focal lengths, such as 6.5 mm, or tiny ranges of focal length, like 7 mm to 21 mm. Because the image-sensor area is smaller than a film frame, you can't compare the lens focal length of a digital camera with that of a film camera. So, instead of (or in addition to) the actual small focal length, most digital-camera makers also post the equivalent 35-mm focal length.
	Zoom. Zoom provides the ability to vary the focal length of a lens between wide angle and telephoto, usually by pressing a button or turning a ring on the lens. With zoom, you'll get wide-angle to telephoto coverage in a single lens. The zoom ratio is usually expressed as a number followed by X, which stands for the number of times the focal length is doubled. A 3X zoom doesn't yield as much wide-angle or telephoto coverage as a 4X or 7X zoom. By the way, don't be fooled when manufacturers boast of digital zoom capability. Optical zoom is the physical focal length of the lens, and it alone produces excellent image quality. Digital zoom is a software method of spreading the pixels farther apart to make the image fill up the picture frame. True optical zoom provides far greater image quality. Digital zoom can actually degrade image quality.
	Macro. This is a function that allows a lens to get very close to the subject, usually to take pictures of small items. In the macro mode, the lens can capture an object 12 inches away or closer, with some cameras able to get as close as half an inch. Most (but not all) digital cameras have a macro mode that extends the normal focal range of the camera so it can shoot items close up.
	Auxiliary lens. This is an optional wide-angle or telephoto lens that screws in or otherwise attaches directly in front of the primary lens (on most cameras that accept such lenses). Once attached, the lens either magnifies the subject or increases the viewable area. The downside to using an auxiliary lens is that it adds weight and bulk to a camera, can be used only with the camera's LCD viewfinder (not the eye-level viewfinder), and reduces light reaching the image sensor by from one to two f-stops.

Flash:

	Built-in. Most digital cameras come equipped with a built-in electronic flash, also called a strobe (or strobe light). Because they are small and low-powered, most digital-camera flashes have a limited range, usually only 10 to 14 feet. Firing the flash drains the camera's battery more quickly, so you won't get as many shots as you will with flash turned off.
	Auto-flash. A feature that fires the flash only when additional light is needed. This is determined by the camera's light sensor, which reads a scene or subject. When an environment is bright enough, the flash doesn't fire. Auto-flash, however, doesn't read backlit situations very well, which is why most digital cameras have a Fill Flash mode.
	Auxiliary flash. All prosumer and professional digital cameras, as well as high-end consumer models, come equipped with a port (also called a hot shoe) that lets you attach an external strobe. An external strobe is better than your camera's built-in flash in certain situations because it can illuminate much farther, control the flash's direction (so you can minimize harsh shadows), recycle faster for quicker performance, and help save your camera's battery.
	Flash intensity. Some digital cameras have a feature that lets you vary the amount of light that the flash emits to give you more precise control over the lighting of the subject.
	Fill flash. A flash mode that turns the flash on for every shot, fill flash is used primarily to illuminate backlit situations in which the subject is slightly darker than the background. For instance, when a person is standing in shade, but the background is in sunlight, then the fill flash will add enough light to balance the exposure of both the person and the background. For better photos, you should always keep it activated when shooting people—even outdoors and in bright light.
	Red-eye reduction. A quick preflash that activates before the actual flash and just before you take a picture. This multiple series of flashes supposedly reduces the devilish red eyes that you see in people or animals looking directly at the camera. A more effective way to eliminate red eye is to use an auxiliary flash. When all else fails, you can erase red eye using image-editing software.
	Rear-curtain sync. Also known as slow sync, this feature triggers the camera's built-in flash when the photo is being taken. This features sets the flash to add illumination to the subject in a low-lit or nighttime scene while leaving the shutter open long enough to record background details. When used effectively, rear-curtain sync brightens a background and illuminates a subject perfectly. Without it, a background would appear black.

Playback:

	Thumbnail. A very small representation of your image displayed on the camera's LCD viewfinder. On most digital cameras, a series of four or nine thumbnails are displayed simultaneously, allowing you to scroll through them quickly by pressing the camera's four-way arrows.
	Zoom and Pan options. Options that let you magnify a saved picture on your LCD viewfinder, so you can see it in greater detail. You can also pan around the magnified image by pressing the camera's four-way arrows.
	Slide show. A playback option that lets you automatically view and display images on the LCD viewfinder. Most digital cameras with slide-show capability also have a video-out port, which allows you to display your images on a TV. Some cameras let you program how long each image is displayed, and a few even offer special effects for transitioning between images.
	Sizing and copying. Some digital cameras allow you to shoot full-resolution pictures and then resize them for posting on the Web or making smaller prints. With this option, you don't have to shoot photos at a low resolution only to discover later that you really wanted to use a better quality setting. Copying allows you to save images to another memory card, a safety feature that ensures you don't accidentally erase or overwrite precious images.

Connectivity:

	Direct connection. This is the most common method for connecting your camera to your computer to download images. Almost all digital cameras attach to a computer via a USB cable, though older models may still use a serial connection. Professional digital cameras (and digital-video camcorders) may use FireWire, which is a faster connection. Many digital cameras use the USB Mass Storage classification, which means that the camera is automatically recognized as a disk drive when it is attached to your PC. This feature lets you drag and drop image files from your camera to your hard drive under Windows without any special software or drivers.
	Card reader. A small, self-powered external drive that reads your camera's memory card and can be attached to your computer via a USB port. To transfer your images from your digital camera to your computer, just slip the memory card into the reader (some readers and cards require an additional adapter), and the computer will recognize it as a hard drive. Make sure to buy the right card reader or adapter for your camera's memory card type and purchase a cable that is long enough to position the reader conveniently.
	Dock. A model-specific cradle that connects your digital camera to your computer. To operate, you simply place the camera in the dock, press a single button (some docks will work automatically), and it will interface with your computer to upload images and launch software for editing, e-mailing, and printing. This is the easiest method for connecting and transferring your pictures to your computer. An added bonus is that most docks double as battery rechargers for cameras equipped with rechargeable batteries.
	Wireless. A few of the newest generation of digital cameras have wireless connectivity built in or via add-on cards. This feature allows you to transmit images wirelessly from the camera to a nearby cell phone, laptop, or desktop. Of course, you must have a wireless receiver at the other end for it to work.

Power source:

Batteries. Although the useful life of batteries has vastly improved over the past year, digital cameras often can suck the power out of batteries in a matter of minutes. To avoid the expense and inconvenience of frequently replacing batteries, either select a model that comes with a set of rechargeable batteries or buy rechargeable batteries and a recharger. And for extra insurance, invest in a second set of rechargeable batteries.

AC adapter. Because they are not bundled with most digital cameras, you should consider buying an AC adapter for your digital camera. This valuable accessory allows you to shoot from a tripod or remain tethered to a computer for as long as you wish. An AC adapter draws power from an electrical outlet, thus saving batteries and ensuring continued shooting. Incidentally, many digital cameras with rechargeable batteries ship with a recharger but no AC adapter.

Exposure controls:

	Auto-exposure. The default option on most digital cameras. Auto-exposure gives the camera total exposure control, without requiring you to set anything. A sensor on the camera measures the light reflected from a scene or subject and automatically sets the optimum combination of f-stop (aperture) number and shutter speed.
	Exposure value compensation. Also known as EV, exposure compensation lets you adjust overall brightness or darkness in precise increments. If all the pictures you take seem dark, you can bump up the exposure compensation toward the plus side of the scale, and vice versa. High-end digital cameras have two to three f-stop EV settings in both directions, in one-third f-stop increments. Less-expensive cameras have one to two f-stop EV in both directions, in only one-half f-stop increments.
	Shutter priority. A feature that lets you set the shutter speed and automatically maintain perfect exposure. When you increase the shutter speed to capture action shots, the camera automatically reduces the f-stop setting. If you decrease shutter speed, the aperture increases, thus maintaining the same exposure values.
	Aperture priority. A feature that lets you set the f-stop number and automatically maintain perfect exposure. A higher f-stop number, which sets the aperture to a smaller lens opening, will increase your depth of field. A lower f-stop number will cause your background and foreground to have a soft focus. As you change the aperture, the camera automatically changes the shutter speed to allow the right amount of light to hit the image sensor needed to take the photograph.
	Manual exposure controls. Features designed for advanced photographers that enable the shutter speed and f-stop to be adjusted independently of each other.
	Burst mode. Many digital cameras have the ability to take a series of pictures in a very short amount of time. This is especially useful when you're shooting sporting events, kids, animals, or other subjects that often require a motor drive–like sequence so you don't miss a frame. Keep in mind that you won't be able to use the camera's flash in burst mode, and it will take a few seconds longer than usual to save all the images, increasing the wait time before the camera's ready to shoot again.
	Auto-bracketing. A command that sets the camera to capture a series of photos of the same scene or subject, with each shot set at a slightly different exposure setting. Most cameras auto-bracket for three frames, though some allow five-frame bracketing. And while most cameras auto-bracket by varying f-stops, some high-end models let you choose auto-bracketing by f-stop or shutter speed. A handful of digital cameras allow you to auto-bracket white balance as well as exposure.
	Best-shot selector. This feature captures four or nine shots almost instantaneously. Each frame has a slightly different exposure or white balance setting. This feature is similar to auto-bracketing, except you get to choose which images you want to save; the others are discarded automatically. Some best-shot selectors allow the camera's intelligence to select the best exposed and sharpest images automatically.

Other image controls:

	White balance. Both film and digital cameras need help in determining how things will look under various lighting conditions. If whites look correct, the rest of the colors in your photo should appear closer to what you see in your real-world scene or subject. This is known as white balance. All digital cameras can automatically adjust the color of your picture so that white always looks white, regardless of the light source. For more accurate color, better cameras give you the option to set white balance manually or choose a preset light source.
	Program mode. Presets designed to prepare your camera to take special types of photographs automatically. Program modes can include settings for night scenes, sports and action subjects, portraits, sepia/black-and-white images, and other shooting environments or conditions.
	Image enhancements. Settings that let you either intensify or tone down certain aspects of your pictures. High-end digital cameras offer settings that let you boost or reduce contrast, brightness, color saturation, and sharpness. Some family-oriented cameras have a type of image enhancement called special effects that lets you add fireworks or borders, for example.
	Panorama. A feature that allows you to shoot a sequence of images, each from a slightly different position and stitch them together into a single photograph. Some digital cameras assist you by displaying overlapping guides for each consecutive image in your LCD viewfinder before you shoot, which results in better panoramas. Other camera makers simply provide software to perform this function. And there are some cameras that offer a panorama mode, which is simply one ultra-wide but shallow shot.

Image management:

	Folders. Folders organize groupings of image files saved and stored on your digital camera's memory card. Digital cameras that offer this feature usually let you name or number each folder and designate which folder you want each picture to be saved in. Folders can be useful for multiuser businesses or families, as well as for photographers who want to organize their pictures according to projects or clients.
	Numbering options. Most digital cameras automatically reset the sequence of your pictures back to 1 every time you swap memory cards. A few models number your pictures sequentially and consecutively, regardless of how many different memory cards you use. Some digital cameras offer a choice of either option. Like folders, this feature is best suited for business users or prolific photographers.
	Metadata. The technical information your digital camera automatically saves with every picture can be displayed on playback or when editing the image on your computer. At the most basic level, metadata lists the date and time when you shot the picture. Some digital cameras record much more extensive metadata, which may include exposure settings, shooting modes, the name of the camera, and even user-definable information.

Special Features:

	Movie mode. Many digital cameras have the ability to capture motion as well as still images; some cameras even can record sound and video. Because of technical limitations, most shoot video at low resolutions suitable for the Web and record at speeds slower than true video's 24 frames per second, giving videos a jerky look. Most cameras allow you to record from 30 seconds to 2 minutes of video, and a few models have the ability to record an hour or more. The ability to shoot photos and record video is a convenient alternative to buying both a digital camera and a video camcorder.
	Audio recording and annotation. Many digital cameras have the ability to record brief 5- to 15-second audio annotations of just-shot photos for identification or captioning. Some models can be used as digital tape recorders, capable of capturing hours of music or conversation.
	Infrared shooting. There's at least one digital camera currently on the market with a long zoom lens that can take pictures in total darkness, which is great for nighttime surveillance or photographing wild animals. It works by illuminating the subject with an invisible infrared light on the camera. A bonus feature is the ability to use this digital camera's electronic viewfinder to observe what's happening in the dark in real time.
	Time/date stamp. This feature is different from the time and date listed in the metadata because it actually appears as part of the image. The time and date are stamped directly and permanently on the image.
	Time lapse. This feature lets you take a series of pictures of a subject over a period of minutes or hours. You put your digital camera on a tripod, select the interval desired (usually from 1 second to 1 hour), press the shutter, and the camera will continue to take shots until you turn it off or the memory card fills up. Time lapse photography is great fun for recording blossoming flowers, cloud movements, shadows throughout the day, and so on.
	Watermarking. A common objection to digital photography is that it's too easy to alter a digital photo, so you never know whether it's reality or simply creative image editing. At least one model offers watermarking, the ability to put a stamp of authentication proving that the image appears exactly as it was shot. You'll know instantly if a single pixel is changed. While watermarking doesn't mean much to the average user, it's invaluable to law enforcement, insurance adjusters, and scientific/medical photographers.