To some extent a digital camera works in the same way as a traditional camera. Both consist of a dark box with a lens that focuses light to create an image. However, a traditional camera focuses the light onto film, whereas a digital camera focuses it onto an electronic sensor that stores the image in flash memory, usually an SD Card.
Digital cameras have a small screen that allows you to view pictures without transferring them to a computer, so you can choose to keep or delete images before transferring them. The digital images can be transferred to a computer via a USB or Firewire cable or by inserting the SD Card into a card reader.
They can then be edited using software like Adobe Photoshop, or the Graphics Image Manipulation Program (GIMP), a free open-source alternative. You can lighten or darken the picture, remove “red eye”, scale the image or crop it and apply various effects.
Most digital cameras have a small screen that allows you to view pictures immediately, without transferring them to a computer, so you can decide whether you want to keep pictures or transfer them. The resolution of digital cameras varies from 8 to 32 megapixels. A pixel (picture element) is a single dot of colour. A megapixel is roughly a million pixels. Higher resolution improves the quality and sharpness of pictures.
Digital images can be printed using a digital photo printer. These use special paper and ink, so the price is likely to work out around the same as having your pictures printed by a photo lab. In addition you can email images to your friends, and upload them to social networking sites like Facebook, or photo-sharing sites, like Flickr. You can also insert them into documents or presentations.
Compact cameras, also known as “point-and-shoot” cameras are small and portable and are particularly suitable for casual use. Most of them have a retractable lens which allows a slim camera to have a fairly long focal length and use a larger image sensor than a camera phone.Images are normally stored in compressed form as JPEG files. Most compact cameras have a built-in low power flash and use a simple autofocus system.
Bridge cameras are higher-end models that physically resemble DSLRs and share some of their advanced features, but they generally use a fixed lens and a small sensor. Many models offer a manual focus mode. They are called bridge cameras because they bridged the gap between compact cameras and the original DSLRs, which were very expensive.
Digital single-lens reflex cameras (DSLRs) are based on film single-lens reflex cameras (SLRs). They have larger sensors than the simpler cameras and use a viewing system in which a mirror reflects light from the lens through a separate optical viewfinder. When taking a picture the the mirror flips out of the way, allowing light to fall on the image sensor.
DSLR cameras can use interchangeable lenses. Each manufacturer has a range of lenses specifically designed for their cameras and lenses are also available from third-party manufacturers. The user can select suitable lenses for different a applications, eg: wide-angle, telephoto, low-light, etc.
Mirrorless interchangeable-lens cameras (MILCs) are a relatively new development which combines the larger sensors and interchangeable lenses of DSLRs with the viewing system of compact cameras, either through an electronic viewfinder or on the rear LCD. They are smaller and simpler than DSLRs since they lack the mirror box. The best-known MILC system is Micro Four Thirds.
You can find lots of useful information about he different types of digital cameras and their features in CNET’s Digital Camera Buying Guide.