ABOUT DIGITAL CAMERA TECHNIQUE

A digital camera is an electronic device used to capture and store photographs electronically in a digital format, instead of using photographic film like conventional cameras, or recording images in an analog format to magnetic tape like many video cameras. Modern compact digital cameras are typically multifunctional, with some devices capable of recording sound and/or video as well as photographs. In the Western market, digital still cameras now outsell their 35 mm film counterparts.

Some definition and explanations

Pixel or picture element- A pixel is a point in a picture. The more points a picture has, the clearer is the picture, and the more information about shapes can be stored in the picture. Each picture in a digital camera or a computer is expressed by a combination of digital bits, for example 16 bits. The bits code for color and lightness or darkness.

Usually the pixel has a code for the intenisty of each color in  a blending of three or four colors such as  red, green, and blue, or cyan, magenta, yellow, and black. In this way most real color nuances can be reproduced with a great accuracy.

Megapixel - This is one million pixels.

Color depth - This is the maximum number of distinct colors that can be coded in a pixel. It is dependent upon the number of bits representing the pixel.
 - 8 bpp, 28 = 256 colors
 - 16 bpp, 216 = 65536 colors - known as Highcolor or Thousands
 - 24 bpp, 224 = 16,777,216 colors - known as Truecolor or Millions
-  48 bpp; for all practical purposes a continuous colorspace, used in many flatbed scanners and for professional work

Resolution - This the number of pixels in a picture, of sensor elements in the image sensor of a camera, or the number of pixels that is possible to show on a medium, for example a screen. It is either expressed as the plain number or as the number of pixels when counting in two directions form an streight agle.

Standard display resolutions include:

VGA 0.3 Megapixels = 640×480
SVGA 0.5 Megapixels = 800×600
XGA 0.8 Megapixels = 1024×768 (sometimes called XVGA)
SXGA 1.3 Megapixels = 1280×1024
SXGA+ 1.4 Megapixels = 1400×1050
UXGA 1.9 Megapixels = 1600×1200
WUXGA 2.3 Megapixels = 1920×1200
QXGA 3.1 Megapixels = 2048×1536
WQXGA 4.1 Megapixels = 2560×1600
QSXGA 5.2 Megapixels = 2560×2048
WQSXGA 6.6 Megapixels = 3200×2048
QUXGA 7.7 Megapixels = 3200×2400
WQUXGA 9.2 Megapixels = 3840×2400

Raster graphics - By raster graphics elements in a picture is stored as pixels and manipulated as pixel collections. Raster graphics are normally used for photography and moovie production.

Vector graphics - By vector graphics elementary figures of a picture are stored as mathematical equations telling where the pixels shall be on the image, and the equations are manipulated. Before display the equations are calculated to render the dispalyable raster based picture. Vector grafics is suitable for animation.

Live-preview digital cameras

The term digital still camera (DSC) most commonly refers to the class of live-preview digital cameras, cameras that use an electronic screen as the principal means of framing and previewing before taking the photograph. All use either a charge-coupled device (CCD) or a CMOS image sensor to sense the light intensities across the focal plane.

Many modern live-preview cameras have a movie mode, and a growing number of camcorders can take still photographs. However, even a low-end live-preview camera can take better still pictures than a mid-range video camera, and mid-range live-preview cameras have much lower video quality than low-end video cameras; that is, products are not generally optimized for both still and video photography, due to their different requirements.

Among live-preview cameras, most have a rear liquid crystal display for both preview and reviewing photographs. Transfers to a computer are commonly carried out using the USB mass storage device class (so that the camera appears as a drive) or using the Picture Transfer Protocol (PTP) and its derivatives; in addition, Firewire is sometimes supported.

The live-preview cameras are typically divided into compact (and subcompact) and bridge (or prosumer) cameras.

Compact digital cameras

Also called digicams, this encompasses most digital cameras. They are characterized by great ease in operation and easy focusing; this design allows for limited motion picture capability. They tend to have significantly smaller zooms than prosumer and DSLR cameras. They have an extended depth of field. This allows objects at a larger range of depths to be in focus, which accounts for much of their ease of use. It is also part of the reason professional photographers find their images flat or artificial-looking. They excel in landscape photography and casual use. They typically save pictures in only the JPEG file format.

Digital single lens reflex cameras

A digital single-lens reflex camera (digital SLR or DSLR) is a digital camera that operates on the same optical and mechanical principles as a modern electronic autofocus 35mm film single-lens reflex camera. The key difference is that the film is replaced with a CCD or CMOS image sensor plus accompanying electronics, thus creating images digitally in-camera, without the need to first chemically develop a latent image on film.

The ability to exchange lenses, to select the best lens for the current photographic need, and to allow the attachment of specialized lenses, is a key to the popularity of DSLR cameras. This feature is also shared by rangefinder cameras, both film and digital, such as the Epson R-D1 and the Leica M8. Some compact cameras offer optional converters that attach to the end of their fixed lenses in order to mimic the ability to use multiple lenses.

The diameters of the lenses for DSLRs are generally larger than for compact point-and-shoots, resulting in more light captured from the subject, allowing the option of using faster shutter speeds, especially in the case of low-light or moving subjects.

In the digital era, zoom lens design is sufficiently advanced to almost eliminate most of the market for non-SLR cameras with interchangeable lenses, so digital camera lens interchangeability is, in practice, mostly restricted to the digital SLR. Compact digital cameras (non-SLR) have a fixed lens which will zoom from medium wide-angle to medium telephoto, omitting only fish-eye and extreme telephoto.

Most lenses intended for film cameras can be used on DSLR cameras provided the lens mounts are the same, but the reverse is not always true. Newer lenses may use the same style of mount as film cameras, but have newer electronics for image stabilization and image control that a film camera would not recognize. Other lenses designed specifically for DSLR (e.g. Canon EF-S lenses) may not fit on the corresponding film or full-frame bodies; others will fit but their image circle may not cover the full film area and therefore yield an incomplete fram.

Bridge cameras

Bridge or "prosumer" digital cameras are high-end live-preview digital cameras (LPDs). They are comparable in size and weight to the smallest digital single-lens reflex cameras (DSLRs), but they lack the mirror and reflex system that characterize DSLRs. The terms "bridge" and "prosumer" characterize the way in which these cameras form a niche between the professional DSLRs and the consumer compacts. Although bridge cameras join consumer compacts in the LPD category, they are sometimes confused with DSLRs due to their similar bodies and larger lenses (as compared to the compacts).


Fujifilm FinePix S9000Bridge cameras tend to have superzoom lenses, which compromises – in varying degrees, depending on the quality of the zoom lens – a "do it all" ability with barrel distortion and pincushioning. Prosumer cameras are sometimes marketed as and confused with digital SLR cameras since the bodies resemble each other. The distinguishing characteristics are that prosumer cameras lack the mirror and reflex system of DSLRs, have so far been always produced with only one single sealed (non-interchangeable) lens (but accessory wide angle or telephoto converters can be attached to the front of the sealed lens), can usually take movies, record audio and the scene composition is done with either the liquid crystal display or the electronic viewfinder (EVF). The overall performance tends to be slower 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 the these cameras can save in JPEG or RAW format.

Digital rangefinders

A rangefinder is a focusing mechanism once widely used on film cameras, but much less common in digital cameras. The term rangefinder alone is often used to mean a rangefinder camera, that is, a camera equipped with a rangefinder.

For information on digital rangefinders specifically, check the digital rangefinder section in the main article linked above.

Professional modular digital camera systems

This category includes very high end professional equipment that 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 35mm.

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 seen in the hands of consumers.
 

(Most elements in this article are taken from wikipedia.org, and as such the article is free to reuse.)

Up to top