Photography science

Summary

Photography is the process of forming images on surfaces sensitive to electromagnetic radiation. These surfaces are usually silver halide-based film or an electronic photosensor, and the radiation recorded is usually visible light, infrared radiation, ultraviolet radiation, or X-rays. Photography is an important technological tool for examining and documenting the natural and human-built world. For more than 150 years, photography has added vital knowledge to the physical, environmental, biological, medical, forensic, materials, and engineering sciences.

Definition and Basic Principles

Photography is the process of forming images on surfaces sensitive to electromagnetic radiation. Usually, the surfaces are either a silver halide-based film or an electronic (digital) photosensor designed to be sensitive to visible light. Depending on the application, the film or electronic sensor may be designed to form images in response to infrared radiation, ultraviolet radiation, or X-rays.

Background and History

The word photography derives from the Greek words photos and graphos, which together mean “light drawing.” Experiments in the precursor technologies of photography date back to ancient times, including the pinhole camera and later the camera obscura, a device used by artists to assist in drawing. Thomas Wedgwood allegedly made photographs as far back as the 1790s but had no way to stabilize the image to make them permanent. The first permanent photographic images were made by the French inventor Nicéphore Niépce using photosensitive bitumen of Judea, including the first image of a natural scene, taken in 1826. In 1833, Hercules Florence, working independently in Brazil, produced prints of drawings during experiments with light-sensitive silver salts (his pioneering work would remain largely unknown until the 1970s). Meanwhile, Niépce and Louis Daguerre in France and William Henry Fox Talbot in England continued to improve their methods of capturing and preserving images. Talbot's work led preeminent scientist John Herschel to coin the word photography in 1839 to describe Talbot's process for fixing an image. Because of Herschel's broad connections to the scientific community, he is traditionally credited with introducing the words photography and photograph.

The invention of photography was announced to the world on January 7, 1839, at a meeting of the French Academy of Sciences in Paris, France. François Arago, a physicist and secretary of the academy, announced that Daguerre had employed the action of light to permanently fix an image with the aid of a camera obscura. Daguerre's image was made on a highly polished, light-sensitized silver plate, which produced a one-of-a-kind image called a daguerreotype.

Several months after Arago announced the daguerreotype, Talbot announced his process for fixing an image by the action of light. In contrast to Daguerre's process, which relied on a light-sensitized silver plate, Talbot's process relied on light-sensitized paper. Talbot's process, which he called photogenic drawing, produced a stable paper negative from which multiple prints could be made. Talbot went on to improve his process of producing images called calotypes, after the Greek word kalos, which means beautiful. Although the daguerreotype was sharper and more detailed than the calotypes, the paper-based calotype is more similar to the modern photograph.

How It Works

The camera is a device that consists of three componentsa light-tight box containing a light-sensitive surface (such as film or a digital sensor), a lens for focusing the light onto the surface, and a means for controlling the exposure, such as a mechanical or electronic shutter. With a film-based camera, image processing takes place outside the camera, often in a darkroom or image-processing laboratory. With digital photography, image capture, processing, and storage occur within the camera.

Film-based cameras are designed in various formats, although the three main formats are 35 millimeter (mm), medium format, and large format view. The type of camera format plays an important role in image quality. Typically, larger format cameras produce higher-quality images. Because each format differs sharply in portability, the choice of format depends largely on the application. Traditional photographic techniques are based on chemistry. In most film-based cameras, the film is coated with silver halide, a light-sensitive compound suspended in gelatin. The film characteristics, such as grain, light sensitivity, and overall image quality, depend on the size, shape, and distribution of the silver-halide crystals. The film's sensitivity to light is denoted by its International Organization for Standardization (ISO) number. Film characterized as slow has a low ISO number, such as ISO 50, whereas film characterized as fast has a high ISO number, such as ISO 400. The film grain becomes increasingly apparent as the ISO number increases. Correspondingly, the image quality tends to decrease as the ISO number increases.

Digital cameras are designed with a light-sensitive electronic sensor that records image information. The sensor comprises an array of photosensors that convert light to electric signals. The signals are proportional to the intensity of the light and are assigned numbers, which the image processor uses to create individual picture elements called pixels. The pixels contain information on brightness (luminance) and color (chrominance). The camera's computer chips then process the digital information to produce the image stored in the camera's memory.

Digital cameras generally use two types of digital sensorsthe charge-coupled device (CCD) and the complementary metal-oxide semiconductor (CMOS). The CCD and CMOS sensors differ primarily in how they convert charge to voltage. In the CMOS sensor, the conversion occurs at each photosensor, whereas in the CCD sensor, the conversion occurs at a common output amplifier. The advantages of the CCD sensor over the CMOS are its higher dynamic range and very low noise levels. The benefits of the CMOS sensor over the CCD are that it is less costly to produce and requires less power.

Digital cameras are designed with image sensors of varying sizes. The size of the sensor and the number of pixels contained on the sensor play an important role in image quality. Rapid technological advances in sensor design have resulted in dramatic improvements in the dynamic range recorded by the sensors and the reduction of digital noise in long exposure and low-light conditions.

Digital photography has several advantages over film photography. For example, image composition and exposure can be reviewed immediately. If necessary, images can be deleted to free up file space on the camera's memory card, and many more photographs can be stored compared to a roll of film. There is no need for film or chemical processing in a darkroom. Color temperature can be changed with different lighting situations to ensure color fidelity on the image. Images can be transferred almost instantly and wirelessly to remote locations or uploaded onto the Internet. Digital images are easily edited using image processing software. The flexibility of digital images, along with the increasing image quality and decreasing price of equipment in the first decades of the twenty-first century, led to the increasing popularity of digital photography in virtually all fields of photography. However, film photography remains in use in some applications, especially as an aesthetic choice in artistic photography, though mostly as a niche market.

Applications and Products

Aerial Photography. First accomplished with balloons in the nineteenth century and with aircraft and satellites in the twentieth century, aerial photography has enabled scientists to acquire information from platforms above the Earth's surface. That information is used to characterize and track changes in land use, soil erosion, agricultural development, water resources, vegetation distribution, animal and human populations, and ecosystems. It is also used to detect water pollution, monitor oil spills, assess habitats, and provide the basis for geologic mapping. Because aerial photographs can record wavelengths of electromagnetic radiation that are invisible to the human eye, such as thermal infrared radiation, plant canopy temperatures can be measured and displayed on an aerial photograph that characterizes the plant's stress due to environmental conditions. Aerial photography is a form of remote sensing.

By applying photogrammetric methods, whereby spatial relationships on an aerial photograph are related to spatial relationships on Earth's surface, analysts can relate distances on the photograph to distances on the ground. Object heights and terrain elevations can also be obtained by comparing photographs made from two different vantage points, each with a different line of sight.

Additional information can be gleaned from aerial photographs by examining tonal changes and shadow distributions within the photograph. Tonal changes are related to surface texture, which can be used to distinguish between vegetation type, soil type, and other surface features. Because the shapes of shadows change with time of day and are unique to particular objects, such as bridges, trees, and buildings, the shadows can be used to aid in the identification of the objects.

Environmental Photography. As the environment changes because of human activities and natural forces such as floods and earthquakes, documenting those changes has become increasingly important. Photography has played, and will continue to play, an important role in that documentation process. For example, scenes photographed in the nineteenth century by such preeminent photographers as William Henry Jackson, Timothy O'Sullivan, and Carleton Watkins as part of government-sponsored surveys of the American West were used to acquire scientific data about the geology and geomorphology of the land. In the twenty-first century, those same scenes are being photographed from the same vantage points and under similar lighting conditions to document the environmental changes that have occurred since the mid-nineteenth century. Environmental photographs from land-based and elevated platforms, such as airplanes and satellites, provide valuable visual information for monitoring present-day and future environmental changes involving ecological systems, snowpacks, forests, deserts, soils, water sources, and the human-built landscape. Such information aids in habitat restoration, land-use planning, and environmental policymaking.

Medical Photography. Photography has been an integral part of medical science since the mid-nineteenth century. In 1840, one year after the invention of photography was announced to the world, Alfred Donné, a Paris-based physician, used a microscope-daguerreotype to photograph bone and dental tissue. In 1865, in a presentation to the Royal Society, British physician Hugh Welch Diamond advocated using photography to document mental patients for later analysis. In the late nineteenth century, Frederick Glendening, a London-based pioneer in medical photography, used clinical photographs of the human body to assist in the diagnosis of disease. At around the same time, Thomas R. French and George Brainerd collaborated to produce the first photographs of the larynx, while W. T. Jackman and J. D. Webster are believed to have made the first photographs of the human retina. The first X-ray photographs were made by Wilhelm Conrad Röntgen in 1895. Since then, X-ray photographs have become a routine tool for medical diagnostics.

Medical photography, also known as biomedical photography, has become a highly specialized field that requires precision and accuracy to be an effective diagnostic tool. Because medical photography is deeply rooted in digital technology, involving, for example, X-rays, magnetic resonance imaging (MRI), and positron emission tomography (PET), practitioners must be well versed in digital imaging techniques. Additional training in the biological sciences, medical sciences, photogrammetry, and photomicrography may be required depending on the area of specialization.

Scientific Photography. In addition to aerial photography, environmental photography, and medical photography, there are many other specialties that fall under scientific photography. Kirilian photography involves using electrophotography to form a contact print, for example, by applying high-voltage but low current to an object on a photosensitive surface. Some uses are primarily for record-keeping or documentation, including archaeological photography (images of past human remains and artifacts taken on-site at excavations or in laboratories), forensic photography (documentary images that can be used in the legal process or admitted as evidence in court), and time-lapse photography (images taken at specified time intervals to show movement or change over time. Botanical photography involves taking images of plants, paying particular attention to their botanical and morphological adaptations, to aid in the identification and study of environmental stresses, diseases, and their interactions with other plants and animals. In biological photography, which sometimes uses optical and electron microscopy, images are taken of plant and animal specimens from micro to macro scales and in land and aquatic environments. In underwater photography, waterproof cameras or traditional cameras in unmanned or manned submersibles are used to photograph underwater scenes. Astrophotography uses both Earth-based and satellite platforms to reproduce images of celestial objects.

Careers and Course Work

Photography is a broad field with many specialty areas and applications. The best preparation for a career in photography is to earn a bachelor of fine arts degree or a bachelor of science degree with elective courses in fields related to specific photographic specializations. Beyond a core of liberal arts courses, general coursework should include classes in the materials and processes of photography, general art classes, the history of art and architecture, studio photography, studio drawing, two-dimensional design, and computer science. Although a master's degree is not required for most careers in photography, the additional graduate-level training may be beneficial for some areas of specialization, such as fine arts photography, architectural photography, and biomedical photography.

For photographic specialties in the physical, medical, or engineering sciences, additional coursework is recommended in chemistry, physics, mathematics, applied computer science, data analysis, imaging systems, and technical writing.

For a photography career specializing in the environmental sciences, additional coursework in meteorology, climate science, soil sciences, ecology, and hydrology is recommended. For a photography career in the biological sciences, perhaps photographing wildlife, plants, or insects, additional courses in wildlife management, biology, entomology, and related fields would be beneficial. A career in forensic photography, which focuses on the documentation of accident and crime scenes for law enforcement and disaster scenes for the insurance industry, may require additional training in underwater photography, the principles of photogrammetry, and criminal justice.

Because academia, industry, and government will continue to have an increasing demand for accurate visual information and visual communication skills, career opportunities in photography should continue to grow for those individuals who are best prepared academically.

Social Context and Future Prospects

Since Daguerre “imprisoned” light in the mid-nineteenth century, photography has profoundly influenced art and science. In the hands of the artist, the camera has heightened awareness of the aesthetic qualities of space and light while revealing hidden truths about culture and society. From centuries-old experiments in optics and chemistry to the digital revolution, the camera has relied on science for its development while also serving as an essential scientific tool for probing and documenting the natural and human-built world.

In its relatively short life, photography has evolved rapidly and profoundly. During the nineteenth century, the newer wet plate collodion process greatly improved the slow exposure times associated with the daguerreotype and calotype processes. Film was eventually introduced, shortening the exposure times even more. The shorter exposure times combined with improved lens optics enabled scientists of the nineteenth century to study phenomena that were too quick for the unaided eye to see. Photographs of galloping horses, humans in motion, birds in flight, lightning, and distant galaxies were among the phenomena studied through photography.

At the beginning of the twenty-first century, digital photography largely supplanted film photography. Digital photography's rapid growth and development enabled the near-immediate sharing of visual information, which aided in monitoring the environment, diagnosing diseases and health problems, documenting crime scenes by law enforcement, and disseminating images by the news media. Digital cameras continued to diminish in size and price and improve in resolution and noise reduction. The ease of digital image-making, especially as digital cameras become smaller and less conspicuous, also raised issues concerning personal privacy and image-making in public venues.

After decades of study, in 2024, researchers at Simon Fraser University (SFU) developed an artificial intelligence (AI) model that understood the perception of light. Photographs have two layers—the lighting effects and the true colors of items in the scene. This concept long presented challenges for scientists who describe separating a photograph's composition as unbaking a cake. Because of SFU's invention, light and colors in a photo can be edited separately using an AI-driven intrinsic decomposition technique. Visuals that were only achievable using computer-generated imagery (CGI) are possible with this technique. For example, adding another person to a photograph is more realistic using this technology. It separates the lighting and true colors of the two images, analyzes them, and creates a unified image true to color and lighting. This technology also has applications in filmmaking. Other technological advancements likely to change photography's future include drone photography, AI-guided photography, and 360-degree photography.

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