Cameras, Digital. Digital Photography

Digital photography constitutes the most revolutionary development in photography since the early experiments of image making on chemically sensitized materials in the 1820s, just as digital computing technologies revolutionized the manner in which the written word was recorded in the latter half of the twentieth century.

The invention of flexible film in the late nineteenth century profoundly changed the course of photography, but the adoption of electronic media 100 years later as a substitute for film constitutes an even more fundamental upheaval, with broad implications for the future of visual communication.

At the end of the twentieth century electronic imaging seemed poised to render chemically processed photographs obsolete, and the future of film appeared to be in doubt as improvements in the quality and capacity of electronic imaging occurred at a dizzying rate.

Digital photography blends three distinct technologies: traditional photographic methodology, video, and digital computer systems. The advent of television and the cathode-ray tube provided both the technology and the conceptual framework for the production of images on an electronic screen instead of film or paper.

The digital computer offered the means for rendering not only text but pictures, broken into tiny picture elements called pixels, which could approximate continuous-tone pictorial representations if the number of constituent pixels was large enough and their size small enough to resist detection by the eye.

Video and computer technologies are electronic cousins, although the first uses analog means and the latter digital. A half century’s experience in viewing images on a television screen provided a conceptual basis for the easy reception and popularization of digitally produced images on a computer monitor, and the notion of transmitting televised imagery in the air has its parallel in the transmission of digital imagery via the Internet. Very quickly the concept of imprinting digital images on paper would threaten the traditional chemically based photographic print.

The computer scanner initially served as an intermediate tool between traditional photography and the digital camera. The rise of the Internet created a demand for transmitting photographic imagery, and scanners converted photographs into electronic files which could be viewed on a computer monitor and shared, either by recording them on a medium such as a floppy disk for exchange with other computer users, or by transmitting them via various file-sharing protocols, including the familiar e-mail systems in common use.

Computer printers could convert electronic image files into prints, which eventually rivaled the ordinary chemically based photographic print. The rise of electronic image editing and manipulation programs, such as Adobe Photoshop, served to aid in the preparation of scanned images. At first digital photography was largely confined to this conversion of film-based photographs into electronic copies, but soon a new generation of cameras emerged to produce direct electronic images without an intermediate chemically processed photograph at all.

This method, interacting directly with a computer, is especially attractive because it completely eliminates the time-consuming steps of chemical processing and the scanning.

There are two types of electronic still cameras, the still video camera and the digital. Both are similar to film cameras except that a built-in light- sensitive computer chip or ‘‘imaging array,’’ either a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS), takes the place of film to capture images. The electronic era in still photography essentially began in 1981 with the introduction of Sony’s Mavica video camera, but still video was an analog system. The Dycam digital camera initiated the fully digital era in 1990.

When light enters the digital camera through the lens and strikes the chip, it emits an electrical charge which is measured electronically and is then sent to the electronic memory (buffer) of the camera. It is then compressed into a format; for example, a JPEG, and transferred to the memory card or disk. Some cameras need to wait for the completion of this process before another picture can be taken, while others have a buffer large enough to hold several pictures, thus enabling rapid ‘‘burst’’ shooting for a group of consecutive pictures.

The CCD has millions of receptors to record the amount of light striking them. Each sensor represents a pixel or image element. The information on the chip is read one horizontal line at a time into the internal memory of the camera, combining the individual pixels into an image, before it is saved to the memory medium of the camera, from which it can be viewed or printed via a computer.

Color can be recorded with a digital camera in several ways. Some cameras use three separate sensors with a separate filter, and light is directed to the sensors by a beam splitter. Another method is to rotate a series of red, green, and blue filters in front of a sensor, but the continuous movement of the filter wheel requires stationary subjects.

Another sophisticated idea places a permanent filter over each sensor and utilizes an interpolation process to approximate color patterns. Most consumer cameras use a single sensor with alternating rows of green-red and green-blue filters in what is called a Bayer filter pattern.

The quality of a digital photograph depends upon a complex combination of factors. The higher the resolution, the more closely the image resembles a continuous-tone analog image. Resolution in film-based photography relates to both the ability of the camera lens and the recording medium to reproduce or ‘‘resolve’’ fineness of detail; in digital photography the number and size of the pixels that constitute the image, control resolution.

The larger the number and the smaller the size of the pixels, the greater the resolution. Since higher resolution results in greater file size, practical considerations usually mandate a compromise on resolution. Low resolution can be satisfactory for viewing images on a computer monitor, but images to be printed normally require a higher resolution. Most digital cameras permit the photographer to select a ‘‘capture’’ resolution, which can later be modified with the computer and the editing program, but the photographer must also consider the amount of camera system memory the image will consume.

If a preferred resolution setting will utilize too much memory, it may be necessary to select a higher image compression to reduce the file size. The need to manipulate and balance these factors to arrive at acceptable results demonstrates the inherent limitations of digital photography and is one reason that film photography still maintained a strong presence at the end of the twentieth century. Yet the rapid pace of technological advances in computers, software, and digital cameras has led many to assume that film-based photography’s days are numbered.

The convenience of digital media has led many professional and other serious photographers to abandon film-based photography altogether. As the tempo of modern life has accelerated, most newspaper photographers and other photojournalists have embraced digital photography exclusively. ‘‘Wet’’ darkrooms were dismantled because photographers in the field, using expensive, sophisticated digital cameras, can transmit images electronically and get them into print in a fraction of the time required with film cameras; also, chemical photography is considered environmentally unfriendly.

Photographic manufacturers such as Eastman Kodak, Fujifilm, Canon, Pentax, Olympus, Leitz, and Nikon devote an increasingly higher percentage of their product lines to digital cameras, joined by such familiar electronic firms as Sony, Samsung, and Panasonic.

With the major exception of the image recording system, film and many digital cameras have similar design principles, employing a range of shutter speeds and aperture sizes to control exposure. Some digital cameras employ an entirely different exposure system in which the chips in the imagesensor array turn on and off at varying intervals in order to capture more or less light. Other digital cameras vary exposure by varying the strength of the electrical charge that a chip emits in proportion to the amount of light received.

Despite the radical difference of this method, the camera’s sensitivity or ‘‘speed,’’ which may be manually variable, is typically rated according to standard film speed nomenclature. The resolution rating of a camera generally is expressed in megapixels, ranging from one to four and higher. The higher the megapixel rating of the camera, the more expensive it tends to be. The larger the pixel count, the larger an acceptable print that can be made, but the higher the camera price and the more file storage space an image requires.

Early digital cameras used internal or ‘‘onboard’’ memory for file storage, requiring the periodic transfer of images to a computer after the memory was filled before additional pictures could be taken. This limitation was solved by the advent of removable memory devices, such as cards or disks.

Most later digital cameras employed a liquid crystal display screen to preview pictures, which functioned as a viewfinder, as well as to review images stored in the camera, as with a computer monitor; this feature represents a substantial advantage over film cameras, permitting the user to redo an unsatisfactory image before leaving the scene. A variety of innovative specialpurpose and special-feature digital cameras were also marketed.