In a nutshell, a digital camera uses a lens or series of lenses to focuses light onto a sensor. This sensor then records the image electronically and transfers it to the electronic workings of the camera where it is organized, converted into binary digital data, and then stored on fixed or removable memory to be later read by a computer. Of course this is a highly simplified explanation of how a digital camera works.
Most digital cameras' sensors are charge-coupled devices, or CCDs, although some cameras instead have a complementary metal oxide semiconductor, or CMOS. Either way, light is converted into electrical charges, which are transferred to the brain, and finally onto the storage media.
As we all learned in grade school, there are three primary colors. Digital cameras use filters to divide the light into those three colors during the conversion process. Good quality cameras have three separate sensors for filtering, with each sensor matching one strand of light.
The amount of light reaching the sensor is also controlled carefully. Cameras do this in two ways: aperture size, and shutter speed. Most of today's cameras have automated aperture settings, although some models allow manual control, which enthusiasts and professionals prefer. Shutter speed is generally set electronically.
There are four kinds of lenses used by digital cameras: optical-zoom lenses with automatic focus; fixed-focus, fixed-zoom lenses; digital-zoom lenses; and replaceable lens systems. Optical zoom lenses have both telephoto and wide options, while the fixed focus and fixed zoom lenses are used in the ordinary, inexpensive cameras that infrequent users own. The digital zoom lens creates the illusion of a zoom effect by culling pixels from the central part of the image and enlarging them to fill the frame. This, however, often results in a grainy or fuzzy image at the extreme limits of the camera's capabilities.
Most digital cameras come with an LCD screen to preview images or to look at them after capture. Most LCD screens are rather small, because the size of the cameras overall is small, too. For better viewing, you must transfer the image to a computer. For quality of image, the biggest factor is the resolution, which is measured in megapixels. The higher the resolution, generally the better the image quality.
Resolution also plays a role in the quality and size of the printed photographs. A cell phone camera or other low quality camera with a one megapixel resolution will produce images that are really only good for emailing or web pages, not printing. With a 2-megapixel camera, the images are good for printing at 4x6 inch sizes or so, while a 4-megapixel camera can be detailed enough to produce good prints at 16x20 inch size. With prices falling continually, if you love photos and hope to make some enlargements, you are best to only consider cameras above 6-megapixels.
Several years ago, digital cameras stored images onto fixed memory locations inside the camera. Users needed a cable to hook up to a computer in order to transfer images. Today's cameras all use removable, reusable memory media, and are therefore much more flexible and convenient. Larger amounts of storage are easy to purchase, so one can also take higher resolution pictures without fear of running out of memory. Various systems for storage include SmartMedia cards, memory sticks, and CompactFlash cards. Other cameras use microdrives, like little hard drives, or DVDs. Whichever method your camera uses, the convenience and freedom that digital photography allows will turn you into a shutterbug in short order!
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