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From consumer reports:


Important features Digital cameras

Digital cameras are distinguished by their resolution--how many pixels, or picture elements, the image sensor contains. One megapixel equals 1 million picture elements. A 5-megapixel camera can make excellent 8x10s and pleasing 11x14s. There are also 6- to 10-megapixel models, including point-and-shoot ones. These are well-suited for making larger prints or for maintaining sharpness if you want to use only a portion of the original image. Professional digital cameras use as many as 16 megapixels. Price: $100 to $400 for 4 megapixels; $150 to $500 for 5 and 6 megapixels; $300 to $1,000 for 7- to 10-megapixel point-and-shoot models, and up to $1,700 for 10-megapixel SLRs.

Most digital cameras are highly automated, with features such as automatic exposure control (which manages the shutter speed, aperture, or both according to available light) and autofocus.

Instead of film, digital cameras record their shots on flash-memory cards. Compact Flash (CF) and SecureDigital (SD) are the most widely used. Once quite expensive, these cards have tumbled in price--a 512-megabyte card can now cost less than $30. Other types of memory cards used by cameras include Memory Stick Duo and xD.

To save images, you transfer them to a computer, typically by connecting the camera to the computer’s USB or FireWire port, or inserting the memory card into a special reader. Some printers can take memory cards and make prints without putting the images on a computer first. Image-handling software, such as Adobe Photoshop Elements, Jasc Paint Shop, Microsoft Picture It, and ACDSee, lets you resize, touch up, and crop digital images using your computer. Most digital cameras work with both Windows and Macintosh machines.

The file format commonly used for photos is JPEG, which is a compressed format. Some cameras can save photos in the uncompressed TIFF format, but this setting yields huge, storage-hogging files. Other high-end cameras have a RAW file format, which yields the image data with no processing from the camera and might also be uncompressed.

The optical viewfinder is becoming increasingly rare, replaced by larger color LCD monitors. (Some are now as large as 3 inches.) Monitors are very accurate in framing the actual image you get--better than most optical viewfinders--but they might be hard to view in bright sunlight. You can also view shots you’ve already taken on the LCD monitor. Most digital cameras provide a video output, so you can view your pictures on a TV screen.

Many new models let you capture video and sound. Some let you record video in high-quality MPEG4 format, up to 30 frames per second, up to the memory card’s capacity.

A zoom lens provides flexibility in framing shots and closes the distance between you and your subject--ideal if you want to quickly switch to a close shot. The typical 3x zoom on mainstream cameras goes from a moderately wide-angle view (35 mm) to moderate telephoto (105 mm). You can find cameras with extended zoom ranges between 8x and 15x, giving added versatility for outdoor photography. Other new cameras go down to 24 or 28 mm at the wide-angle end, making it easier to take in an entire scene in close quarters, such as a crowded party.

Optical zooms are superior to digital zooms, which merely magnify the center of the frame without actually increasing picture detail, resulting in a somewhat coarser view.

Sensors in digital cameras are typically about as light sensitive as ISO 100 film, though many let you increase that setting. (At ISO 100, you’ll probably need to use a flash indoors and in low outdoor light.) A camera’s flash range tells you how far from the camera the flash will provide proper exposure. If the subject is out of range, you’ll know to close the distance. But digital cameras can tolerate some underexposure before the image suffers noticeably.

Red-eye reduction shines a light toward your subject just before the main flash. (A camera whose flash unit is farther from the lens reduces the risk of red eye. Computer editing of the image may also correct red eye.) With automatic flash mode, the camera fires the flash whenever the light entering the camera registers as insufficient. A few new cameras have built-in red-eye correction.

Some cameras with large LCDs, and some with powerful telephoto lenses, now come with some form of image stabilizer. (Optical-image stabilizers are the best type; some cameras use simulated stabilization to try to achieve the same effect.) Stabilizers compensate for handheld camera shake, letting you use a slower shutter speed than you otherwise could for following movement. But an image stabilizer won’t compensate for the motion of subjects.

Most new 6- to 10-megapixel cameras come with full manual controls, including independent controls for shutter and aperture. That gives serious shutterbugs control over depth of field, shooting action, or shooting scenes with tricky lighting.