Photography | Research & Encyclopedia Articles

The digital imaging technologies commonly used today evolved from technologies created by the National Aeronautics and Space Administration (NASA) and the Jet Propulsion Laboratory in the early 1960s. Government scientists were looking for a way to transmit imaging data more accurately from outer space to Earth. The analog (wave) technologies used at the time were prone to degradation during transmission. The scientists devised a way to digitize the images taken by satellites and rocket mounted cameras. By turning the analog transmission into a digital code, the scientists solved the problems of image degradation. The imaging data could be sent long distances without a loss of quality, thus rendering a more accurate view of distant galactic sights.

The newly invented digital technologies were too expensive for the general public, but they were commonly used by governments, scientists, and corporations for topographic, atmospheric, military, medical, and astronomic purposes. The invention of the microchip, a small yet powerful processor, in the early 1980s enabled the creation of smaller, more affordable digital imaging equipment and the personal computer for the home and small business. The first commercial digital camera appeared in 1981 with the release of the Sony Mavica.

Most digital cameras look similar to and share many common functions of 35mm cameras. Digital cameras have lenses, bodies, and flashes alongwith controls for focus and zoom like traditional cameras. Several manufacturers created a digital back that integrated existing analog cameras with the new digital technologies. Digital backs are mounted onto the back of analog cameras. The sensory mechanism of the digital back takes the place of the film and fits into position on the same plane as the film.

Unlike their film-based predecessors, digital cameras use disks instead of film for storage, and they often have controls for image playback, in-camera special effects, and image editing. These special digital controls enable the photographer to access the picture instantly and decide upon the quality of the image. The image can then either be saved or deleted. These editing functions are enabled by the digital camera's memory (RAM).

The most fundamental difference between digital and analog photography is the way an image is captured. Film-based photographic systems use light sensitive materials, usually a silver halide, to record physically the impression of light bouncing off a subject. A digital camera converts the light bouncing off the subject into a mathematical model that can be read and reconstructed to approximate the original scene.

An image is transformed from analog to digital in the camera using an electronic grid of chips that sense, map, and quantify light. The information from the grid is then sent and converted to digital code by processors. The digital camera's lens projects an analog image onto the grid, and each small square of the grid records the intensity, color, and location of the light. The unit of measure for digital pieces of information is a pixel. The color information is established using three filters: red, green, and blue. The camera does not sense color; it measures the gradations of intensity between the three filters. The processor then converts the information into a code. The light striking each pixel is given a numeric value: 0 for true black through 255 for true white. The numeric value then becomes part of the binary number system (bit code), a code of 0s and 1s eight bits long. This code is what a computer reads, processes, and reconstructs as a photographic image.

The large file size of digital images often makes them hard to process and transmit. To reduce the file size, digital camera images are often converted and stored as JPEG files. JPEGs are a standardized, compressed file type. Through compression and standardization, file sizes are reduced and made more convenient to store and transmit. They are also formatted in a uniform way that makes digital imaging with personal computers more feasible.

Digital cameras for personal use often have relatively poor image quality and small file sizes. A common resolution for a digital photograph is 72 dpi (dots per inch) with pixel dimensions of 640 480. To determine the measurements of a digital image, divide the dimensions (the number of pixels) by the resolution (the number of pixels in an inch). The standard resolution for computer screen based images, like the ones on web pages, is 72 dpi. Digital cameras with higher resolution are available, but because of their expense, they are used mainly for professional or scientific purposes.

The proliferation of digital photography is tied to advances in personal computers and business applications. Many people have taken up digital photography because of the expansion of affordable personal computers into thehome. A computer set up for digital imaging often includes a color monitor, a color printer, a disk drive (compatible with the camera's), a program for image editing, a negative scanner, and a flatbed scanner.

Flatbed scanners have a flat glass bed where an image can be placed, scanned, digitized, and opened in a computer program. The scanner contains a laser-equipped carriage; the laser goes over the length of the bed, scanning the image line by line. The laser beam then reflects information back to the sensors, which convert the information much like a digital camera. A negative scanner works similarly but comes with a guide for the insertion of negatives and transparencies. A drum scanner is used for high quality, professional scanning. With drum scanners the image is placed inside a cylinder that rotates at high speeds while the laser tracks across the image.

Scanners come with software for limited editing in the scanning phase. The image scanned can commonly be adjusted for scale, media, contrast, and color balance. The scanned image is then usually opened in a more sophisticatedprogram. The measure of scanner quality is the bit depth. Digital imaging software uses interpolation to scale images. Interpolation is a method for resampling images to adjust scale. The intensity and value of a group of pixels is established, then that group of pixels is transformed into one pixel with an average value. Extreme shifts in the scale of digital images can result in the loss of image quality; over-interpolation can create blurry, jagged, or pixilated images.

Once loaded on the computer's storage drive, and opened in an image editing program, digital photographs become easily manageable. Images can be edited, montaged, distorted, or completely fabricated while retaining the believability of traditional photographs. Many image-editing programs allow the user to adjust the scale, color balance, contrast, and levels of an image. More complicated programs allow the user to manipulate the image further by adding special effects, filters, and text, copying and pasting other images, painting and drawing, and converting file types. The most common editing program is Adobe PhotoShop, which has become the standard in publishing, design, and academia. Once digital images are edited with the computer, they can be printed, sent via e-mail attachment, opened in other programs, or used to create web pages.

Jim Fike

Art; Desktop Publishing; Fashion Design; Journalism; World Wide Web.

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