Photography And Imagery

The word photograph means literally "something written by light,'' in other words an image created from light. For the first century of its existence, photography referred exclusively to images made using the light-sensitive reaction of silver halide crystals, which undergo a chemical change when exposed to near-ultraviolet, visible, or near-infrared radiation. This photochemical change can be "developed" into a visible picture. All types of film are based on this phenomenon.

Beginning in the mid-20th century, however, new electronic means of creating aerial images came into existence. For example, Landsat I was the first satellite to provide images of the Earth using a remarkable device called the multispectral scanner (MSS). At that time, scanners were viewed with great skepticism by most engineers and scientists for two reasons (Hall, 1992). First, the scanner employed a moving part, an oscillating mirror, which

FIGURE 1-12 Airport at the National Soaring Museum at Harris Hill, near Elmira, New York, United States. Several gliders are visible on and next to the runway. Photo taken with a compact digital camera through the open window of the copilot's seat in an unpowered, two-person glider several 100 m above the ground, an example of an unconventional platform utilized for SFAP. Photo by JSA, July 2005.

FIGURE 1-12 Airport at the National Soaring Museum at Harris Hill, near Elmira, New York, United States. Several gliders are visible on and next to the runway. Photo taken with a compact digital camera through the open window of the copilot's seat in an unpowered, two-person glider several 100 m above the ground, an example of an unconventional platform utilized for SFAP. Photo by JSA, July 2005.

was considered unreliable. Second, the scanner was not a full-frame imaging device; it created images from strips. Cartographers were suspicious of the scanner's geometric integrity. But, the scanner did have one important advantage, its multispectral capability for visible and infrared wavelengths.

Within hours of Landsat's launch in 1972, the first MSS images created a sensation with their amazing clarity and synoptic views of the landscape (Williams and Carter, 1976; Lauer et al., 1997). Landsat imagery revolutionized all types of cartographic, environmental, and resource studies of the Earth (Fig. 1-13). Rapid development of electronic scanners followed for both airborne and space-based platforms, and the remote sensing community embraced many types of sensors and imaging systems during the 1980s and 1990s.

As electronic imagery became more common, many restricted use of the term photograph to those pictures exposed originally in film and developed via photochemical processing. Thus, aerial imagery was classed as photographic or non-photographic; the latter included all other types of pictures made through electronic means. Traditional film-based photographs are referred to as analog images, because each silver halide crystal in the film emulsion records a light level within a continuous range from pure white to pure black. The spatial resolution of a photograph is determined by the size of minute silver halide crystals. In contrast, electronic imagery is typically recorded as digital values, for example 0-255 (28) from minimum to maximum levels, for each picture element (cell or pixel) in the scene. Spatial resolution is given by pixel size (linear dimension).

In the late 20th century, a basic distinction grew up between analog photographs exposed in film and digital images recorded electronically. Analog photographs generally had superior spatial resolution but limited spectral range—panchromatic, color visible, color infrared, etc. Digital imagery lacked the fine spatial resolution of photographs, but had a much broader spectral range and enhanced multispectral capability. Photographic purists maintained the superiority of analog film and viewed electronic imagery as lesser in quality.

The dichotomy between analog and digital imagery faded quickly in the first decade of the 21st century for several reasons. The advantages of digital image storage, processing, enhancement, analysis, and reproduction are major factors spurring adoption by users at all levels—amateur to professional specialist. Analog airphotos are routinely scanned and converted into digital images nowadays. Digital cameras have achieved equality with film cameras in terms of spatial resolution and geometric fidelity (Malin and Light, 2007). Film photography is rapidly becoming obsolete, in fact, except for certain artistic and technical uses and where the lower cost of film remains attractive. For most people today, nonetheless, the word photograph is applied equally to images produced from film

FIGURE 1-13 Early Landsat MSS composite image of the Rocky Mountains and High Plains in south-central Colorado, United States. This false-color composite resembles color-infrared photography; active vegetation appears in red colors. SP = Spanish Peaks, GSD = Great Sand Dunes. NASA ERTS E-2 977-16311-457, September 25, 1977, image adapted from the U.S. Geological Survey, EROS Data Center.

FIGURE 1-13 Early Landsat MSS composite image of the Rocky Mountains and High Plains in south-central Colorado, United States. This false-color composite resembles color-infrared photography; active vegetation appears in red colors. SP = Spanish Peaks, GSD = Great Sand Dunes. NASA ERTS E-2 977-16311-457, September 25, 1977, image adapted from the U.S. Geological Survey, EROS Data Center.

or electronic sensors. We follow this liberal use of the term photograph in this book, in which we place primary emphasis on digital photography regardless of how the original image was recorded.

100 Photography Tips

100 Photography Tips

To begin with your career in photography at the right path, you need to gather more information about it first. Gathering information would provide you guidance on the right steps that you need to take. Researching can be done through the internet, talking to professional photographers, as well as reading some books about the subject. Get all the tips from the pros within this photography ebook.

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