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 Home > By Career > Professional Courses > Photography
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Photography is the art, science and practice of creating durable images by recording
light or other electromagnetic radiation, either electronically by means of an image
sensor or chemically by means of a light-sensitive material such as photographic
film.[1] Typically, a lens is used to focus the light reflected or emitted from
objects into a real image on the light-sensitive surface inside a camera during
a timed exposure. The result in an electronic image sensor is an electrical charge
at each pixel, which is electronically processed and stored in a digital image file
for subsequent display or processing. The result in a photographic emulsion is an
invisible latent image, which is later chemically developed into a visible image,
either negative or positive depending on the purpose of the photographic material
and the method of processing. A negative image on film is traditionally used to
photographically create a positive image on a paper base, known as a print, either
by using an enlarger or by contact printing.
Photography has many uses for business, science, manufacturing (e.g. Photolithography),
art, and recreational purposes.
As far as can be ascertained, it was Sir John Herschel in a lecture before the Royal
Society of London, on March 14, 1839 who made the word "photography" known to the
world. But in an article published on February 25 of the same year in a German newspaper
called the Vossische Zeitung, Johann von Maedler, a Berlin astronomer, had used
the word photography already.[2] The word photography is based on the Greek φῶς
(photos) "light" and γραφή (graphé) "representation by means of lines" or "drawing",
together meaning "drawing with light".
Function
The camera is the image-forming device, and photographic film or a silicon electronic
image sensor is the sensing medium. The respective recording medium can be the film
itself, or a digital electronic or magnetic memory.
Photographers control the camera and lens to "expose" the light recording material
(such as film) to the required amount of light to form a "latent image" (on 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 paper or film.
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. 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. A general principle
known from the birth of photography is that the smaller the camera, the brighter
the image. This meant that as soon as photographic materials became sensitive enough
(fast enough) to take candid or what were called genre pictures, small detective
cameras were used, some of them disguised as a tie pin that was really a lens, as
a piece of luggage or even a pocket watch (the Ticka camera).
The discovery of the 'camera obscura' that provides an image of a scene is very
old, dating back to ancient China. Leonardo da Vinci mentions natural camera obscuras
that are formed by dark caves on the edge of a sunlit valley. A hole in the cave
wall will act as a pinhole camera and project a laterally reversed, upside down
image on a piece of paper. So the invention of photography was really concerned
with finding a means to fix and retain the image in the camera obscura. This in
fact occurred first using the reproduction of images without a camera when Josiah
Wedgewood, from the famous family of potters, obtained copies of paintings on leather
using silver salts. As he had no way of fixing them, that is to say to stabilize
the image by washing out the non exposed silver salts, they turned completely black
in the light and had to be kept in a dark room for viewing.
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The Contax S of 1949 — the first pentaprism SLR.
Lens and mounting of a large-format camera.
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Renaissance painters used the camera obscura which, in fact, gives the optical rendering
in color that dominates Western Art. The Camera Obscura literally means "dark chamber"
in Latin. It is a box with a hole in it which allows light to go through and create
an image onto the piece of paper.
The movie camera is a type of photographic camera which takes a rapid sequence of
photographs on strips of film. 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 together to create the illusion of motion.
Exposure and rendering
Camera controls are inter-related. The total amount of light reaching the film plane
(the 'exposure') changes with the duration of exposure, aperture of the lens, and
on the effective focal length of the lens (which in variable focal length lenses,
can force a change in aperture as the lens is zoomed). Changing any of these controls
can alter the exposure. Many cameras may be set to adjust most or all of these controls
automatically. This automatic functionality is useful for occasional photographers
in many situations.
The duration of an exposure is referred to as shutter speed, often even in cameras
that do not have a physical shutter, and is typically measured in fractions of a
second. It is quite possible to have exposures one of several seconds, usually for
still-life subects, and for night scenes exposure times can be several hours.
The effective aperture is expressed by an f-number or f-stop (derived from focal
ratio), which is proportional to the ratio of the focal length to the diameter of
the aperture. Longer lenses will pass less light even though the diameter of the
aperture is the same due to the greater distance the light has to travel: shorter
lenses (a shorter focal length) will be brighter with the same size of aperture.
The smaller the f/number, the larger the effective aperture. The present system
of f/numbers to give the effective aperture of a lens was standardized by an international
convention. There were earlier, different series of numbers in older cameras.
If the f-number is decreased by a factor of , the aperture diameter is increased
by the same factor, and its area is increased by a factor of 2. The f-stops that
might be found on a typical lens include 2.8, 4, 5.6, 8, 11, 16, 22, 32, where going
up "one stop" (using lower f-stop numbers) doubles the amount of light reaching
the film, and stopping down one stop halves the amount of light.
Image capture can be achieved through various combinations of shutter speed, aperture,
and film or sensor speed. Different (but related) settings of aperture and shutter
speed enable photographs to be taken under various conditions of film or sensor
speed, lighting and motion of subjects and/or camera, and desired depth of field.
A slower speed film will exhibit less "grain", and a slower speed setting on an
electronic sensor will exhibit less "noise", while higher film and sensor speeds
allow for a faster shutter speed, which reduces motion blur or allows the use of
a smaller aperture to increase the depth of field. For example, a wider aperture
is used for lower light and a lower aperture for more light. If a subject is in
motion, then a high shutter speed may be needed. A tripod can also be helpful in
that it enables a slower shutter speed to be used.
For example, f/8 at 8 ms (1/125th of a second) and f/5.6 at 4 ms (1/250th of a second)
yield the same amount of light. The chosen combination has an impact on the final
result. The aperture and focal length of the lens determine the depth of field,
which refers to the range of distances from the lens that will be in focus. A longer
lens or a wider aperture will result in "shallow" depth of field (i.e. only a small
plane of the image will be in sharp focus). This is often useful for isolating subjects
from backgrounds as in individual portraits or macro photography. Conversely, a
shorter lens, or a smaller aperture, will result in more of the image being in focus.
This is generally more desirable when photographing landscapes or groups of people.
With very small apertures, such as pinholes, a wide range of distance can be brought
into focus, but sharpness is severely degraded by diffraction with such small apertures.
Generally, the highest degree of "sharpness" is achieved at an aperture near the
middle of a lens's range (for example, f/8 for a lens with available apertures of
f/2.8 to f/16). However, as lens technology improves, lenses are becoming capable
of making increasingly sharp images at wider apertures.
Image capture is only part of the image forming process. Regardless of material,
some process must be employed to render the latent image captured by the camera
into a viewable image. With slide film, the developed film is just mounted for projection.
Print film requires the developed film negative to be printed onto photographic
paper or transparency. Digital images may be uploaded to an image server (e.g.,
a photo-sharing web site), viewed on a television, or transferred to a computer
or digital photo frame.
Prior to the rendering of a viewable image, modifications can be made using several
controls. Many of these controls are similar to controls during image capture, while
some are exclusive to the rendering process. Most printing controls have equivalent
digital concepts, but some create different effects. For example, dodging and burning
controls are different between digital and film processes. Other printing modifications
include:
• Chemicals and process used during film development
• Duration of print exposure – equivalent to shutter speed
• Printing aperture – equivalent to aperture, but has no effect on depth of field
• Contrast – changing the visual properties of objects in an image to make them
distinguishable from other objects and the background
• Dodging – reduces exposure of certain print areas, resulting in lighter areas
• Burning in – increases exposure of certain areas, resulting in darker areas
• Paper texture – glossy, matte, etc.
• Paper type – resin-coated (RC) or fiber-based (FB)
• Paper size
• Toners – used to add warm or cold tones to black-and-white prints
Uses
Photography gained the interest of many scientists and artists from its inception.
Scientists have used photography to record and study movements, such as Eadweard
Muybridge's study of human and animal locomotion in 1887. Artists are equally interested
by these aspects but also try to explore avenues other than the photo-mechanical
representation of reality, such as the pictorialist movement. Military, police,
and security forces use photography for surveillance, recognition and data storage.
Photography is used by amateurs to preserve memories of favorite times, to capture
special moments, to tell stories, to send messages, and as a source of entertainment.
History
Photography is the result of combining several technical discoveries. Long before
the first photographs were made, Chinese philosopher Mo Di and Greek mathematicians
Aristotle and Euclid described a pinhole camera in the 5th and 4th centuries BC.
In the 6th century AD, Byzantine mathematician Anthemius of Tralles used a type
of camera obscura in his experiments, Ibn al-Haytham (Alhazen) (965–1040) studied
the camera obscura and pinhole camera, Albertus Magnus (1193–1280) discovered silver
nitrate, and Georges Fabricius (1516–71) discovered silver chloride.[12] Daniele
Barbaro described a diaphragm in 1568.[13] Wilhelm Homberg described how light darkened
some chemicals (photochemical effect) in 1694.[14] The fiction book Giphantie, published
in 1760, by French author Tiphaigne de la Roche, described what can be interpreted
as photography.
Invented in the first decades of the 19th century, photography (by way of the camera)
seemed able to capture more detail and information than traditional mediums, such
as painting and sculpting.Photography as a usable process goes back to the 1820s
with the development of chemical photography. The first permanent photoetching was
an image produced in 1822 by the French inventor Nicéphore Niépce, but it was destroyed
by a later attempt to duplicate it.[6] Niépce was successful again in 1825. He made
the first permanent photograph from nature with a camera obscura in 1826.[16] However,
because his photographs took so long to expose (8 hours), he sought to find a new
process. Working in conjunction with Louis Daguerre, they experimented with silver
compounds based on a Johann Heinrich Schultz discovery in 1816 that a silver and
chalk mixture darkens when exposed to light. Niépce died in 1833, but Daguerre continued
the work, eventually culminating with the development of the daguerreotype in 1837.
Daguerre took the first ever photo of a person in 1838 when, while taking a daguerreotype
of a Paris street, a pedestrian stopped for a shoe shine, long enough to be captured
by the long exposure (several minutes). Eventually, France agreed to pay Daguerre
a pension for his formula, in exchange for his promise to announce his discovery
to the world as the gift of France, which he did in 1839.
Meanwhile, Hercules Florence had already created a very similar process in 1832,
naming it Photographie, and English inventor William Fox Talbot had earlier discovered
another means to fix a silver process image but had kept it secret. After reading
about Daguerre's invention, Talbot refined his process so that portraits were made
readily available to the masses. By 1840, Talbot had invented the calotype process,
which creates negative images. Talbot's famous 1835 print of the Oriel window in
Lacock Abbey is the oldest known negative in existence.[18][19] John Herschel made
many contributions to the new methods. He invented the cyanotype process, now familiar
as the "blueprint". He was the first to use the terms "photography", "negative"
and "positive". He discovered sodium thiosulphate solution to be a solvent of silver
halides in 1819, and informed Talbot and Daguerre of his discovery in 1839 that
it could be used to "fix" pictures and make them permanent. He made the first glass
negative in late 1839.
Mid 19th century "Brady stand" photo model's armrest table, meant to keep portrait
models more still during long exposure times (studio equipment nicknamed after the
famed US photographer, Mathew Brady).
In March 1851, Frederick Scott Archer published his findings in "The Chemist" on
the wet plate collodion process. This became the most widely used process between
1852 and the late 1860s when the dry plate was introduced. There are three subsets
to the Collodion process; the Ambrotype (positive image on glass), the Ferrotype
or Tintype (positive image on metal) and the negative which was printed on Albumen
or Salt paper.
Many advances in photographic glass plates and printing were made in through the
19th century. In 1884, George Eastman developed the technology of film to replace
photographic plates, leading to the technology used by film cameras today.
In 1908 Gabriel Lippmann won the Nobel Laureate in Physics for his method of reproducing
colors photographically based on the phenomenon of interference, also known as the
Lippmann plate.
Processes
Black-and-white
All photography was originally monochrome, or black-and-white. Even after color
film was readily available, black-and-white photography continued to dominate for
decades, due to its lower cost and its "classic" photographic look. It is important
to note that some monochromatic pictures are not always pure blacks and whites,
but also contain other hues depending on the process. The cyanotype process produces
an image of blue and white for example. The albumen process, first used more than
150 years ago, produces brown tones.
Many photographers continue to produce some monochrome images, often because of
the established archival permanence of well processed silver halide based materials.
Some full color digital images are processed using a variety of techniques to create
black and whites, and some manufacturers produce digital cameras that exclusively
shoot monochrome.
Color
Color photography was explored beginning in the mid-19th century. Early experiments
in color required extremely long exposures (hours or days for camera images) and
could not "fix" the photograph to prevent the color from quickly fading when exposed
to white light.
The first permanent color photograph was taken in 1861 using the three-color-separation
principle first published by physicist James Clerk Maxwell in 1855. 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 color image. Transparent prints of the images could be projected through
similar color filters and superimposed on the projection screen, an additive method
of color reproduction. A color print on paper could be produced by superimposing
carbon prints of the three images made in their complementary colors, a subtractive
method of color reproduction pioneered by Louis Ducos du Hauron in the late 1860s.
Russian photographer Sergei Mikhailovich Prokudin-Gorskii made extensive use of
this color separation technique, employing a special camera which successively exposed
the three color-filtered images on different parts of an oblong plate. Because his
exposures were not simultaneous, unsteady subjects exhibited color "fringes" or,
if rapidly moving through the scene, appeared as brightly colored ghosts in the
resulting projected or printed images.
The development of color photography was held back 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 photochemist Hermann Vogel in 1873 suddenly made it possible to add sensitivity
to green, yellow and even red. Improved color sensitizers and ongoing improvements
in the overall sensitivity of emulsions steadily reduced the once-prohibitive long
exposure times required for color, bringing it ever closer to commercial viability.
Autochrome, the first commercially successful color process, was introduced by the
Lumière brothers in 1907. Autochrome plates incorporated a mosaic color filter layer
made of dyed grains of potato starch, which allowed the three color 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 color and the tiny colored points blended
together in the eye, synthesizing the color of the subject by the additive method.
Autochrome plates were one of several varieties of additive color screen plates
and films marketed between the 1890s and the 1950s.
Kodachrome, the first modern "integral tripack" (or "monopack") color film, was
introduced by Kodak in 1935. It captured the three color components in a multilayer
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 color couplers during a complex processing procedure. Agfa's similarly
structured Agfacolor Neu was introduced in 1936. Unlike Kodachrome, the color couplers
in Agfacolor Neu were incorporated into the emulsion layers during manufacture,
which greatly simplified the processing. Currently available color films still employ
a multilayer emulsion and the same principles, most closely resembling Agfa's product.
Instant color film, used in a special camera which yielded a unique finished color
print only a minute or two after the exposure, was introduced by Polaroid in 1963.
Color photography may form images as positive transparencies, which can be used
in a slide projector, or as color negatives intended for use in creating positive
color enlargements on specially coated paper. The latter is now the most common
form of film (non-digital) color photography owing to the introduction of automated
photoprinting equipment.
Full-spectrum, ultraviolet and infrared
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.[20] 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) colored 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
& law enforcement, and even some claimed use in ghost hunting.
Digital photography
Traditional photography burdened photographers working at remote locations without
easy access to processing facilities, and competition from television pressured
photographers to deliver images to newspapers with greater speed. Photo journalists
at remote locations often carried miniature photo labs and a means of transmitting
images through telephone lines. 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. 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. The primary 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 imaging has raised ethical concerns because of the ease of manipulating
digital photographs in post-processing. Many photojournalists have declared they
will not crop their pictures, or are forbidden from combining elements of multiple
photos to make "photomontages," passing them as "real" photographs. Today's technology
has made photo editing relatively simple for even the novice photographer. However,
recent changes of in-camera processing allows digital fingerprinting of photos to
detect tampering for purposes of forensic photography.
Digital point-and-shoot cameras have become widespread consumer products, outselling
film cameras, and including new features such as video and audio recording. Kodak
announced in January 2004 that it would no longer sell reloadable 35 mm cameras
in western Europe, Canada and the United States after the end of that year. Kodak
was at that time a minor player in the reloadable film cameras market. In January
2006, Nikon followed suit and announced that they will stop the production of all
but two models of their film cameras: the low-end Nikon FM10, and the high-end Nikon
F6. On May 25, 2006, Canon announced they will stop developing new film SLR cameras.[21]
Though most new camera designs are now digital, a new 6x6cm/6x7cm medium format
film camera was introduced in 2008 in a cooperation between Fuji and Voigtländer.
According to a survey made by Kodak in 2007 when the majority of photography was
already digital, 75 percent of professional photographers say they will continue
to use film, even though some embrace digital.
According to the U.S. survey results, more than two-thirds (68 percent) of professional
photographers prefer the results of film to those of digital for certain applications
including:
• film’s superiority in capturing more information on medium and large format films
(48 percent);
• creating a traditional photographic look (48 percent);
• capturing shadow and highlighting details (45 percent);
• the wide exposure latitude of film (42 percent); and
• archival storage (38 percent)
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