Digital SLRs combine electronic imaging with professional-grade optics.
The digital SLR is the latest take on a camera style that has served photographers well since the 1950s. A digital single lens reflex camera's sophisticated optics provide clear, accurate viewfinder images as well as high-quality photos. Digital imaging replaces the traditional 35 mm film roll with a CCD sensor and electronic data storage. Professionals and serious amateurs alike favor the DSLR format for its ruggedness, versatility, adherence to industry standards and results.
SLR Cameras
Optically, what distinguishes an SLR from other cameras is its viewfinder, the lens through which you frame an image before you press the button. Light passes through the main lens and reflects on a mirror and through a pentaprism, a specially shaped glass prism that corrects the up-down and left-right image reversals produced in the lens. Because you see the image through the lens, the viewfinder represents an image with accurate borders. Everything you see in the viewfinder ends up in the photo you take. Cameras without this feature are notorious for leaving out critical details at the edge of an image. When you press the button to take a photo, the viewfinder mirror in the camera flips up and away, exposing the image sensor to the incoming light. Although a digital SLR may have both an optical viewfinder and an LCD screen, the colors and shades in the viewfinder are more realistic than those produced in the LCD, which tells a good photographer if a subject has the right kind of lighting.
A point-and-shoot camera is too small to accommodate the optics found in an SLR. These lower-priced convenience cameras use LCD screens exclusively.
Digital Imaging Technology
Modern cameras have a sensor called a charge-coupled device that turns light from an image into electronic impulses. The CCD, which won its inventors, Willard S. Boyle and George E. Smith, the 2009 Nobel Prize for Physics, consists of a grid of microscopic, light-sensitive elements on a silicon chip. The smaller the elements on the chip, the more detailed the image. A set of miniature electronic circuits processes the CCD's output signal into a data file stored as a JPEG, MPEG or other industry-standard digital image format. Although point-and-shoot digital cameras also use CCDs, the ones used in DSLRs have a larger surface. The larger chips produce less noise and have improved resolution, producing better images.
Lenses
It takes precision lenses to produce a good-quality photo. The design for a low-cost camera saves money by using smaller, simpler and less precise lenses. A DSLR typically has professional-grade lenses you change to suit different needs. For example, a professional photographer may have lenses for extreme close-ups, portraits, wide-angle images and long-distance shots. The lenses have an industry-standard metal coupling that attaches to the camera body, allowing for quick changes.
Price and Features
Prices for digital SLRs fall in a wide range, from about $100 for a basic single-lens model to professional systems costing tens of thousands of dollars. Most run between $300 and $2,000 for the DSLR camera body and a standard lens; specialty lenses range from about $100 to thousands of dollars. A typical DSLR camera has automatic and manually adjustable shutter speeds as fast as 1/8000 of a second, depending on the model. Quick shutter speeds let you freeze the action of fast-action events, capture time-lapse images and produce other special effects. Modern DSLRs have built-in light and image processing features including settings to accommodate bright sunlight, overcast daylight, and incandescent and fluorescent indoor lights. Although a simple point-and-shoot camera excels in convenience and simplicity, a DSLR is the centerpiece of a serious photographer's toolkit, along with lenses, a tripod, external flash unit and other professional equipment.
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