• Hurter and Driffield began pioneering work on the light sensitivity of photographic emulsions in 1876. Their work enabled the first quantitative measure of film speed to be devised.
• The first flexible photographic roll film was marketed by George Eastman, founder of Kodak in 1885, but this original "film" was actually a coating on a paper base. As part of the processing, the image-bearing layer was stripped from the paper and transferred to a hardened gelatin support. The first transparent plastic roll film followed in 1889. It was made from highly flammable nitrocellulose known as nitrate film.
• Although cellulose acetate or "safety film" had been introduced by Kodak in 1908, at first it found only a few special applications as an alternative to the hazardous nitrate film, which had the advantages of being considerably tougher, slightly more transparent, and cheaper. The changeover was not completed for X-ray films until 1933, and although safety film was always used for 16 mm and 8 mm home movies, nitrate film remained standard for theatrical 35 mm motion pictures until it was finally discontinued in 1951.
• Films remained the dominant form of photography until the early 21st century when advances in digital photography drew consumers to digital formats. Although modern photography is dominated by digital users, film continues to be used by enthusiasts and professional photographers. The distinctive "look" of film-based photographs compared to digital images is likely due to a combination of factors, including (1) differences in spectral and tonal sensitivity (S-shaped density-to-exposure (H&D curve) with film vs. linear response curve for digital CCD sensors), (2) resolution, and (3) continuity of tone.
• Originally, all photography was monochrome, or black-and-white. Even after colour film was readily available, black-and-white photography continued to dominate for decades, due to its lower cost, chemical stability, and its "classic" photographic look. The tones and contrast between light and dark areas define black-and-white photography. Monochromatic pictures are not necessarily composed of pure blacks, whites, and intermediate shades of Gray but can involve shades of one particular hue depending on the process. The cyanotype process, for example, produces an image composed of blue tones. The albumen print process, publicly revealed in 1847, produces brownish tones.
• Many photographers continue to produce some monochrome images, sometimes because of the established archival permanence of well-processed silver-halide-based materials. Some full-colour digital images are processed using a variety of techniques to create black-and-white results, and some manufacturers produce digital cameras that exclusively shoot monochrome. Monochrome printing or electronic display can be used to salvage certain photographs taken in colour which are unsatisfactory in their original form; sometimes when presented as black-and-white or single-colour-toned images they are found to be more effective. Although colour photography has long predominated, monochrome images are still produced, mostly for artistic reasons. Almost all digital cameras have an option to shoot in monochrome, and almost all image editing software can combine or selectively discard RGB colour channels to produce a monochrome image from one shot in colour.
• The first colour photograph made by the three-colour method suggested by James Clerk Maxwell in 1855, taken in 1861 by Thomas Sutton. The subject is a coloured, tartan patterned ribbon.
• Colour photography was explored beginning in the 1840s. Early experiments in colour required extremely long exposures (hours or days for camera images) and could not "fix" the photograph to prevent the colour from quickly fading when exposed to white light.
• The first permanent colour photograph was taken in 1861 using the three-colour-separation principle first published by Scottish physicist James Clerk Maxwell in 1855. The foundation of virtually all practical colour processes, Maxwell's idea was to take three separate black-and-white photographs through red, green and blue filters. This provides the photographer with the three basic channels required to recreate a colour image. Transparent prints of the images could be projected through similar colour filters and superimposed on the projection screen, an additive method of colour reproduction. A colour print on paper could be produced by superimposing carbon prints of the three images made in their complementary colours, a subtractive method of colour reproduction pioneered by Louis Ducos du Hauron in the late 1860s.
• Colour photography was possible long before Kodachrome, as this 1903 portrait by Sarah Angelina Acland demonstrates, but in its earliest years, the need for special equipment, long exposures, and complicated printing processes made it extremely rare.
• Russian photographer Sergei Mikhailovich Prokudin-Gorskii made extensive use of this colour separation technique, employing a special camera which successively exposed the three colour-filtered images on different parts of an oblong plate. Because his exposures were not simultaneous, unsteady subjects exhibited colour "fringes" or, if rapidly moving through the scene, appeared as brightly coloured ghosts in the resulting projected or printed images.
• Implementation of colour photography was hindered by the limited sensitivity of early photographic materials, which were mostly sensitive to blue, only slightly sensitive to green, and virtually insensitive to red. The discovery of dye sensitization by photo chemist Hermann Vogel in 1873 suddenly made it possible to add sensitivity to green, yellow and even red. Improved colour sensitizers and ongoing improvements in the overall sensitivity of emulsions steadily reduced the once-prohibitive long exposure times required for colour, bringing it ever closer to commercial viability.
• Autochrome, the first commercially successful colour process, was introduced by the Lumière brothers in 1907. Autochrome plates incorporated a mosaic colour filter layer made of dyed grains of potato starch, which allowed the three colour components to be recorded as adjacent microscopic image fragments. After an Autochrome plate was reversal processed to produce a positive transparency, the starch grains served to illuminate each fragment with the correct colour and the tiny coloured points blended together in the eye, synthesizing the colour of the subject by the additive method. Autochrome plates were one of several varieties of additive colour screen plates and films marketed between the 1890s and the 1950s.
• Kodachrome, the first modern "integral tripack" (or "monopack") colour film, was introduced by Kodak in 1935. It captured the three colour components in a multi- layer emulsion. One layer was sensitized to record the red-dominated part of the spectrum, another layer recorded only the green part and a third recorded only the blue. Without special film processing, the result would simply be three superimposed black-and-white images, but complementary cyan, magenta, and yellow dye images were created in those layers by adding colour couplers during a complex processing procedure.
• Agfa's similarly structured Agfa colour Neu was introduced in 1936. Unlike Kodachrome, the colour couplers in Agfa colour Neu were incorporated into the emulsion layers during manufacture, which greatly simplified the processing. Currently, available colour films still employ a multi-layer emulsion and the same principles, most closely resembling Agfa's product.
• Instant colour film, used in a special camera which yielded a unique finished colour print only a minute or two after the exposure, was introduced by Polaroid in 1963.
• Colour photography may form images as positive transparencies, which can be used in a slide projector, or as colour negatives intended for use in creating positive colour enlargements on specially coated paper. The latter is now the most common form of film (non-digital) colour photography owing to the introduction of automated photo printing equipment. After a transition period centred around 1995–2005, colour film was relegated to a niche market by inexpensive multi-megapixel digital cameras. Film continues to be the preference of some photographers because of its distinctive "look".
• In 1981, Sony unveiled the first consumer camera to use a charge-coupled device for imaging, eliminating the need for film: the Sony Mavica. While the Mavica saved images to disk, the images were displayed on television, and the camera was not fully digital.
• The first digital camera to both record and save images in a digital format was the Fujix DS-1P created by Fujfilm in 1988.
• In 1991, Kodak unveiled the DCS 100, the first commercially available digital single-lens reflex camera. Although its high cost precluded uses other than photojournalism and professional photography, commercial digital photography was born.
• Digital imaging uses an electronic image sensor to record the image as a set of electronic data rather than as chemical changes on film. An important difference between digital and chemical photography is that chemical photography resists photo manipulation because it involves film and photographic paper, while digital imaging is a highly manipulative medium. This difference allows for a degree of image post-processing that is comparatively difficult in film-based photography and permits different communicative potentials and applications.
• Digital photography dominates the 21st century. More than 99% of photographs taken around the world are through digital cameras, increasingly through smartphones.
• Angles such as vertical, horizontal, or as pictured here diagonal are considered important photographic techniques.
• A large variety of photographic techniques and media are used in the process of capturing images for photography. These include the camera; dual photography; full-spectrum, ultraviolet and infrared media; light field photography; and other imaging techniques.
• The camera is the image-forming device, and a photographic plate, photographic film or a silicon electronic image sensor is the capture medium. The respective recording medium can be the plate or film itself, or a digital magnetic or electronic memory.
• Photographers control the camera and lens to "expose" the light recording material to the required amount of light to form a "latent image" (on plate or film) or RAW file (in digital cameras) which, after appropriate processing, is converted to a usable image. Digital cameras use an electronic image sensor based on light-sensitive electronics such as charge-coupled device (CCD) or complementary metal–oxide–semiconductor (CMOS) technology. The resulting digital image is stored electronically, but can be reproduced on a paper.
• The camera (or 'camera obscura') is a dark room or chamber from which, as far as possible, all light is excluded except the light that forms the image. It was discovered and used in the 16th century by painters. The subject being photographed, however, must be illuminated. Cameras can range from small to very large, a whole room that is kept dark while the object to be photographed is in another room where it is properly illuminated. This was common for reproduction photography of flat copy when large film negatives were used (see Process camera).
• As soon as photographic materials became "fast" (sensitive) enough for taking candid or surreptitious pictures, small "detective" cameras were made, some actually disguised as a book or handbag or pocket watch (the Ticka camera) or even worn hidden behind an Ascot necktie with a tie pin that was really the lens.
• The movie camera is a type of photographic camera that takes a rapid sequence of photographs on recording medium. In contrast to a still camera, which captures a single snapshot at a time, the movie camera takes a series of images, each called a "frame". This is accomplished through an intermittent mechanism. The frames are later played back in a movie projector at a specific speed, called the "frame rate" (number of frames per second). While viewing, a person's eyes and brain merge the separate pictures to create the illusion of motion.
• Photographs, both monochrome and colour, can be captured and displayed through two side-by-side images that emulate human stereoscopic vision. Stereoscopic photography was the first that captured figures in motion. While known colloquially as "3-D" photography, the more accurate term is stereoscopy. Such cameras have long been realized by using film and more recently in digital electronic methods (including cell phone cameras).
• Dual photography consists of photographing a scene from both sides of a photographic device at once (e.g. camera for back-to-back dual photography, or two networked cameras for portal-plane dual photography). The dual photo apparatus can be used to simultaneously capture both the subject and the photographer, or both sides of a geographical place at once, thus adding a supplementary narrative layer to that of a single image.
• Ultraviolet and infrared films have been available for many decades and employed in a variety of photographic avenues since the 1960s. New technological trends in digital photography have opened a new direction in full spectrum photography, where careful filtering choices across the ultraviolet, visible and infrared lead to new artistic visions.
• Modified digital cameras can detect some ultraviolet, all of the visible and much of the near infrared spectrum, as most digital imaging sensors are sensitive from about 350 nm to 1000 nm. An off-the-shelf digital camera contains an infrared hot mirror filter that blocks most of the infrared and a bit of the ultraviolet that would otherwise be detected by the sensor, narrowing the accepted range from about 400 nm to 700 nm.
• Replacing a hot mirror or infrared blocking filter with an infrared pass or a wide spectrally transmitting filter allows the camera to detect the wider spectrum light at greater sensitivity. Without the hot-mirror, the red, green and blue (or cyan, yellow and magenta) coloured micro-filters placed over the sensor elements pass varying amounts of ultraviolet (blue window) and infrared (primarily red and somewhat lesser the green and blue micro-filters).
• Uses of full spectrum photography are for fine art photography, geology, forensics and law enforcement.
• Layering is a photographic composition technique that manipulates the foreground, subject or middle-ground, and background layers in a way that they all work together to tell a story through the image. Layers may be incorporated by altering the focal length, distorting the perspective by positioning the camera in a certain spot. People, movement, light and a variety of objects can be used in layering.
• Digital methods of image capture and display processing have enabled the new technology of "light field photography" (also known as synthetic aperture photography). This process allows focusing at various depths of field to be selected after the photograph has been captured. As explained by Michael Faraday in 1846, the "light field" is understood as 5-dimensional, with each point in 3-D space having attributes of two more angles that define the direction of each ray passing through that point.
• These additional vector attributes can be captured optically through the use of microlenses at each pixel point within the 2-dimensional image sensor. Every pixel of the final image is actually a selection from each sub-array located under each microlens, as identified by a post-image capture focus algorithm.
• Devices other than cameras can be used to record images. Trichome of Arabidopsis thaliana seen via scanning electron microscope. Note that image has been edited by adding colours to clarify structure or to add an aesthetic effect. Heiti Paves from Tallinn University of Technology.