A digital camera (or digicam for short) is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor.
Front and back of a Canon PowerShot A95.

Many compact digital still cameras can record sound and moving video as well as still photographs. In the Western market, digital cameras outsell their 35 mm film counterparts.

Digital cameras can do things film cameras cannot: displaying images on a screen immediately after they are recorded, storing thousands of images on a single small memory device, recording video with sound, and deleting images to free storage space. Some can crop pictures and perform other elementary image editing. Fundamentally they operate in the same manner as film cameras, typically using a lens with a variable diaphragm to focus light onto an image pickup device. The combination of the diaphragm and a shutter mechanism is used to admit the correct amount of light to the imager, just as with film; the only difference is that the image pickup device is electronic rather than chemical.

Digital cameras are incorporated into many devices ranging from PDAs and mobile phones (called camera phones) to vehicles. The Hubble Space Telescope and other astronomical devices are essentially specialised digital cameras.

Wednesday, October 28, 2009

Bridge cameras



Bridge or SLR-like cameras are higher-end digital cameras that physically and ergonomically resemble DSLRs and share with them some advanced features, but share with compacts the use of a fixed lens and a small sensor. Like compacts, most use live preview to frame the image. Autofocus is achieved using the same contrast-detect mechanism, but many bridge cameras feature a manual focus mode for greater control.
Fujifilm FinePix S9000.

Due to the combination of large physical size but a small sensor, many of these cameras have very highly specified lenses with large zoom ranges and fast apertures, partially compensating for the inability to change lenses. A typical example is the lens on the Panasonic FZ50, a 35-420mm equivalent lens with an aperture of 1:2.8-3.7. To reduce aberrations in a lens with such ambitious specifications, these have quite complex constructions, using multiple aspheric elements and often anomalous-dispersion glass. To compensate for the reduced sensitivity of their small sensors, these cameras almost always include an image stabilization system of some kind to enable longer handheld exposures.

These cameras are sometimes marketed as and confused with digital SLR cameras since the appearance is similar. Bridge cameras lack the reflex viewing system of DSLRs, have so far been fitted with fixed (non-interchangeable) lenses (although in some cases accessory wide-angle or telephoto converters can be attached to the lens), can usually take movies with sound, and the scene is composed by viewing either the liquid crystal display or the electronic viewfinder (EVF). They are usually slower to operate than a true digital SLR, but they are capable of very good image quality (with sufficient light) while being more compact and lighter than DSLRs. The high-end models of this type have comparable resolutions to low and mid-range DSLRs. Many of these cameras can store images in a raw image format, or processed and JPEG compressed, or both. The majority have a built-in flash similar to those found in DSLRs.
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