In October 1957, with the launch of Sputnik, the Russians, under the leadership of Sergei Korolev, won the first leg of the space race over the American program led by Werner Von Braun. And so the quest to develop digital photography was launched.
What did the space race have to do with photography? Wasn’t it about putting a man in orbit, space stations, landing on the moon, and intercontinental nuclear weapons delivery? In fact it was about all those things, but in 1957 the biggest interest and concern regarding satellites was their ability to carry cameras that could spy on your enemies. The goal then was to capture an image from space, but the technology of the day required film, which had to be returned to earth either by recovering the satellite itself or by recovering a film capsule ejected by the satellite. This process entailed the risk of imagery loss if the aerial or sea recovery procedure failed. Even when recovery was successful, the imagery was not immediately available in a time-sensitive situation. These limitations led to research on the means of capturing imagery data and transmitting that data electronically to ground stations. This research led to the development of imaging sensors and processors that have brought us the digital photography we take for granted today.
The immediate approach to the spy satellite problem was to build on videotape technology developed by Bing Crosby Enterprises (yes, that Bing Crosby) in 1951 for the budding television industry. Video cameras employed a cathode ray tube that swept an electron beam though a photoconducting layer onto a target plate. When light from a subject fell on the photoelectric layer, the layer’s electrical resistance changed in inverse proportion to the brightness of the light. As the cathode tube beam swept the target plate, the varying resistances would paint an image, with high voltages for bright areas and low voltages for darker areas. These streaming voltages thus comprised live image signals that could then be captured in videotape recorders on magnetic tape. Early spy satellites converted these linear analogue signals into digital signals via encoding protocols. The digital signals could then be transmitted to earth, where encoders could convert them back to video images. The resolution of the tube’s continuously sweeping raster scan dictated the fidelity of the resulting images. The limitations of this analogue approach led researchers to explore technologies that would permit capture of images directly into a digital signal.
The next development occurred in 1957, when Russell Kirsch developed the drum scanner, which detected and saved the varying light intensities of an image in a binary, or digital signal, employing the then novel concept of a mosaic of small square picture elements, or pixels. In October 1969, George Smith and Willard Boyle, of Bell Labs, invented the charge-coupled-device (CCD), a solid-state device that directly converts light into electric signals. With each CCD sensor acting as a pixel, measuring the intensity of the light falling on it, a CCD sensor array could be used to capture a mosaic image. This concept saw reality in 1973 when Fairchild Imaging produced the first commercial CCD imager, a 0.01 megapixel (100 x 100 pixels) chip.
These ideas finally bore fruit in 1975, when Eastman Kodak engineer Steven Sasson patented a prototype digital camera employing a Fairchild CCD and a lens from a Kodak movie camera. This camera, weighing nearly 9 pounds, and about the size of a toaster, captured 0.01 megapixel images, and needed 23 seconds to store each monochrome digital image on digital cassette tape, which could hold a total of 30 images.
The next year, another Eastman Kodak scientist, Bryce Bayer, invented a color filter array for use with a grid of photosensors. Much like the 100-year-old Autochrome process used dyed potato starch grains in a random filter matrix to capture a full color image, the Bayer array employs a checkerboard-like filter matrix of red, green, and blue pixels to capture a color image. While each discrete pixel is filtered to record only red, green, or blue, a demosaicing algorithm is employed to interpolate between adjacent pixels and generate a full color image. To address the physiology of the human eye, the Bayer filter mosaic uses twice as many green filter elements as red or blue ones.
While other worthy mosaic filter configurations have been tried, the Bayer filter has predominated to date. More recently, the Foveon X3 sensor has been developed, which acts more like traditional color film with its RGB dye layers. The Foveon chip uses three layers of photosensors, each layer being sensitive to blue, green, or red light. In this manner, the sensor captures the total color at each pixel location, without interpolation as in a Bayer chip. However, the stacked sensor layers attenuate the light falling on the chip, reducing the Foveon chip’s low-light capabilities versus mosaic matrix alternatives.
For the next thirty years, digital camera technology progressed in an evolutionary fashion, introducing over time increased resolution, i.e., more megapixels, better low-light capabilities, improved image processing algorithms, improved memory systems, Wi-Fi connectivity, and better ergonomic features. Notable milestones include:
• 1981: Sony sells the Mavica, a 570×490 pixel camera that captured video stills on 2-inch floppy disks
• 1988: The first Joint Photographic Experts Group (JPEG) and Moving Picture Experts Group (MPEG) imagery coding standards were established
• 1991: The Kodak DCS, based on a stock Nikon F3 35mm film camera modified to use a 1.3 megapixel Kodak sensor and a shoulder-carried processing and storage unit, is released with a retail price of $20000
• Also in 1991: The Dycam Model 1, or Logitech Fotoman, is released as the first consumer digital camera, offering 376×240 pixel monochrome images, volatile memory (stored pictures were lost with a dead or removed battery), and a price of $995
• 1994: SanDisk produced the first PC Card, a compact storage medium with non-volatile memory
• 1995: The $1000 Casio QV-10 debuted as the first camera featuring a color LCD panel that could be used as a viewfinder and to playback captured images.
• 1997: The first digital cameras featuring complementary metal-oxide-semiconductor (CMOS) sensors appeared, with their lower production costs and lower power consumption than comparable CCD sensors
• 1999: The Nikon D1, the first digital SLR, was released, offering the professional market a digital alternative to film with a 2.74MP sensor at a cost of $5500
• Also in 1999: Sharp and Kyocera introduce the first camera phones
• 2003: Canon launched the Digital Rebel, a 6MP DSLR aimed at the consumer market, priced just under $1000
• 2007: the Apple iPhone, while not the first camera phone, introduced a superior user interface, innovative sharing tools, and third-party add-on applications to bring camera phone imaging into the mainstream
• 2008: Panasonic eschewed the reflex mirror/pentaprism assembly and introduced the mirrorless interchangeable-lens compact (ILC) camera, a new class of digital camera
• 2011: Lytro releases the first camera based on light-field or plenoptic photography, which captures the available light from a scene from multiple directions, allowing post-capture manipulation of depth of field and focus.
The digital medium, both for professional and amateur users, has come to surpass film as the reigning photographic paradigm. The merging of still photography with action video, the explosion of innovative post-capture processing software options, and the ceaseless development of new optics and sensor capabilities point the art towards unknown and exciting possibilities. But then, that is the future, not the history of photography…
(Next Time: Early Portrait Photography)
This is the tenth installment of an ongoing series on the history and development of the art of photography. It is inspired by the History of Photography class previously taught by Professor Jeff Curto in the College of DuPage Photography Program. While not a slavish copy of his work, I freely admit to following Curto’s general course outline and sharing many of the perspectives he has developed. I would encourage anyone with a greater interest in this subject to follow his course online via video podcasts, at http://photohistory.jeffcurto.com.
A World History of Photography, 4th Ed, 2007 by Naomi Rosenblum
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