Classification

Digital cameras can be classified into several categories

Video cameras
Video cameras are classified as devices to record moving images.
Video cameras are classified as devices to record moving images.
* Professional video cameras such as those used in television and movie production. These typically have multiple image sensors (one per color) to enhance resolution and color gamut. Professional video cameras usually do not have a built-in VCR or microphone.
* Camcorders used by amateurs. They generally include a microphone to record sound, and feature a small liquid crystal display to watch the video during taping and playback.
* Webcams are digital cameras attached to computers, used for video conferencing or other purposes. Webcams can capture full-motion video as well, and some models include microphones or zoom ability.

In addition, many live-preview digital cameras have a "movie" mode in which images are continuously acquired at a frame rate sufficient for video.


Live-preview digital cameras
The term digital still camera (DSC) usually implies a live-preview digital camera, which uses an electronic screen, usually a rear-mounted liquid crystal display, as the principal means of framing and previewing before taking the photograph, and for viewing stored photographs. All use either a charge-coupled device (CCD) or a CMOS image sensor to sense the light intensities across the focal plane.

Many live-preview cameras have a movie mode, and many camcorders can take still photographs. However, still cameras take better still photographs than camcorders, and vice versa; there is still a need for distinct still and motion picture cameras.

Images may be transferred to a computer, printer or other device in a number of ways: the USB mass storage device class makes the camera appear to the computer as if it were a disk drive; the Picture Transfer Protocol (PTP) and its derivatives may be used; Firewire is sometimes supported; and the storage device may simply be removed from the camera and inserted into another device.

Live-preview cameras may be compact or subcompact, or the larger and more sophisticated bridge cameras.


Compact digital cameras
Compact cameras are designed to be small and portable; the smallest are described as subcompacts. Compact cameras are usually designed to be easy to use, sacrificing advanced features and picture quality for compactness and simplicity; images can only be stored using lossy JPEG compression. Most have a built-in flash usually of low power, sufficient for nearby subjects. They may have limited motion picture capability. Compacts often have macro capability, but if they have zoom capability the range is usually less than for bridge and DSLR cameras. They have a greater depth of field, allowing objects within a large range of distances from the camera to be in sharp focus. They are particularly suitable for casual and "snapshot" use.


Bridge cameras or SLR like
Bridge or SLR-like cameras are higher-end live-preview cameras that physically resemble DSLRs and share with them some advanced features, but share with compacts the live-preview design and small sensor sizes.

Bridge cameras often have superzoom lenses which provide a very wide zoom range, typically 12:1, which is attained at the cost of some distortions, including barrel and pincushion distortion, to a degree which varies with lens quality. These cameras are sometimes marketed as and confused with digital SLR cameras since the appearance is similar. Bridge cameras lack the mirror and reflex 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 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 lossless RAW format as an option to lossy JPEG compression. The majority have a built-in flash, often a unit which flips up over the lens. The guide number tends to be between 11 and 15.


Digital single lens reflex cameras

Digital single-lens reflex cameras (DSLRs) are digital cameras based on film single-lens reflex cameras (SLRs), both types are characterized by the existence of a mirror and reflex system. See the main article on DSLRs for a detailed treatment of this category.


Digital rangefinders

A rangefinder is a user-operated optical mechanism to measure subject distance once widely used on film cameras. Most digital cameras measure subject distance automatically using acoustic or electronic techniques, but it is not customary to say that they have a rangefinder. The term rangefinder alone is sometimes used to mean a rangefinder camera, that is, a film camera equipped with a rangefinder, as distinct from an SLR or a simple camera with no way to measure distance.


Professional modular digital camera systems

This category includes very high end professional equipment that can be assembled from modular components (winders, grips, lenses, etc.) to suit particular purposes. Common makes include Hasselblad and Mamiya. They were developed for medium or large format film sizes, as these captured greater detail and could be enlarged more than 35 mm.

Typically these cameras are used in studios for commercial production; being bulky and awkward to carry they are rarely used in action or nature photography. They can often be converted into either film or digital use by changing out the back part of the unit, hence the use of terms such as a "digital back" or "film back". These cameras are very expensive (up to $40,000) and are typically not used by consumers.


Line-scan camera systems
A line-scan camera is a camera device containing a line-scan image sensor chip, and a focusing mechanism. These cameras are almost solely used in industrial settings to capture an image of a constant stream of moving material. Unlike video cameras, line-scan cameras use a single array of pixel sensors, instead of a matrix of them. Data coming from the line-scan camera has a frequency, where the camera scans a line, waits, and repeats. The data coming from the line-scan camera is commonly processed by a computer, to collect the one-dimensional line data and to create a two-dimensional image. The collected two-dimensional image data is then processed by image-processing methods for industrial purposes.

Line-scan technology is capable of capturing data extremely fast, and at very high image resolutions. Usually under these conditions, resulting collected image data can quickly exceed 100MB in a fraction of a second. Line-scan-camera–based integrated systems, therefore are usually designed to streamline the camera's output in order to meet the system's objective, using computer technology which is also affordable.

Line-scan cameras intended for the parcel handling industry can integrate adaptive focusing mechanisms to scan six sides of any rectangular parcel in focus, regardless of angle, and size. The resulting 2-D captured images could contain, but are not limited to 1D and 2D barcodes, address information, and any pattern that can be processed via image processing methods. Since the images are 2-D, they are also human-readable and can be viewable on a computer screen. Advanced integrated systems include video coding and optical character recognition (OCR).

credit : From Wikipedia