New Nikon Releases Today!!!
giovedì 19 agosto 2010
giovedì 3 dicembre 2009
History of photography
The word photography derives from the Greek words 'photos' - meaning light and 'graphein' - to write. The word was popularised by Sir John Herschel in 1839. Modern photography began in the 1820s with the first permanent photographs.
A camera obscura box used for drawing images
Photography is the result of combining several technical discoveries. Long before the first photographs were made, Chinese philosopher Mo Ti and Greek philosophers such as Aristotle and Euclid described a pinhole camera in the 5th and 4th centuries B.C.E,[2][3] Ibn al-Haytham (Alhazen) (965–1040) studied the camera obscura and pinhole camera,[3][4] Albertus Magnus (1193/1206-1280) discovered silver nitrate, and Georges Fabricius (1516-1571) discovered silver chloride. Daniel Barbaro described a diaphragm in 1568. Wilhelm Homberg described how light darkened some chemicals (photochemical effect) in 1694. The novel Giphantie (by the French Tiphaigne de la Roche, 1729-1774) described what can be interpreted as photography.
For years images have been projected onto surfaces. According to the Hockney–Falco thesis as argued by artist David Hockney,[5] some artists used the camera obscura and camera lucida to trace scenes as early as the 16th century. However, this theory is heavily disputed by today's contemporary realist artists who are able to create high levels of realism without optical aids.[6] These early cameras did not record an image, but only projected images from an opening in the wall of a darkened room onto a surface, turning the room into a large pinhole camera. The phrase camera obscura literally means dark chamber. While this early prototype of today's modern camera may have had modest usage in its time, it was an important step in the evolution of the invention.
Nicéphore Niépce's earliest surviving photograph of a scene from nature, circa 1826, "View from the Window at Le Gras," Saint-Loup-de-Varennes (France).
"Boulevard du Temple", taken by Louis Daguerre in late 1838 or early 1839, was the first-ever photograph of a person. It is an image of a busy street, but because exposure time was over ten minutes, the city traffic was moving too much to appear. The exception is a man in the bottom left corner, who stood still getting his boots polished long enough to show up in the picture.
Robert Cornelius, self-portrait, Oct. or Nov. 1839, approximate quarter plate daguerreotype. The back reads, "The first light picture ever taken." This self-portrait is the first photographic portrait image of a human ever produced.
The first permanent photograph was an image produced in 1825 by the French inventor Joseph Nicéphore Niépce. His photographs were produced on a polished pewter plate covered with a petroleum derivative called bitumen of Judea. Bitumen hardens with exposure to light. The unhardened material may then be washed away and the metal plate polished, rendering a negative image which then may be coated with ink and impressed upon paper, producing a print. Niépce then began experimenting with silver compounds based on a Johann Heinrich Schultz discovery in 1724 that a silver and chalk mixture darkens when exposed to light.
In partnership, Niépce (in Chalon-sur-Saône) and Louis Daguerre (in Paris) refined the existing silver process.[7] In 1833 Niépce died of a stroke, leaving his notes to Daguerre. While he had no scientific background, Daguerre made two pivotal contributions to the process. He discovered that exposing the silver first to iodine vapour before exposure to light, and then to mercury fumes after the photograph was taken, could form a latent image. Bathing the plate in a salt bath then fixes the image. On January 7, 1839 Daguerre announced that he had invented a process using silver on a copper plate called the daguerreotype.[8] The French government bought the patent and immediately made it public domain.
In 1832, French-Brazilian painter and inventor Hercules Florence had already created a very similar process, naming it Photographie.
After reading about Daguerre's invention, Fox Talbot worked on perfecting his own process; in 1839 he got a key improvement, an effective fixer, from John Herschel, the astronomer, who had previously showed that hyposulfite of soda (also known as hypo, or now sodium thiosulfate) would dissolve silver salts. Later that year, Herschel made the first glass negative.
By 1840, Talbot had invented the calotype process. He coated paper sheets with silver chloride to create an intermediate negative image. Unlike a daguerreotype, a calotype negative could be used to reproduce positive prints, like most chemical films do today. Talbot patented[9] this process, which greatly limited its adoption. He spent the rest of his life in lawsuits defending the patent until he gave up on photography. Later George Eastman refined Talbot's process, which is the basic technology used by chemical film cameras today. Hippolyte Bayard had also developed a method of photography but delayed announcing it, and so was not recognized as its inventor.
In 1851 Frederick Scott Archer invented the collodion process.[citation needed] Photographer and children's author Lewis Carroll used this process.[citation needed]
Roger Fenton's assistant seated on Fenton's photographic van, Crimea, 1855.
Slovene Janez Puhar invented the technical procedure for making photographs on glass in 1841.[citation needed] The invention was recognized on July 17, 1852 in Paris by the Académie Nationale Agricole, Manufacturière et Commerciale.
Herbert Bowyer Berkeley experimented with his own version of collodian emulsions after Samman introduced the idea of adding dithionite to the pyrogallol developer.[citation needed] Berkeley discovered that with his own addition of sulfite, to absorb the sulfur dioxide given off by the chemical dithionite in the developer, that dithionite was not required in the developing process. In 1881 he published his discovery. Berkeley's formula contained pyrogallol, sulfite and citric acid. Ammonia was added just before use to make the formula alkaline. The new formula was sold by the Platinotype Company in London as Sulpho-Pyrogallol Developer.[10]
Nineteenth-century experimentation with photographic processes frequently became proprietary. The German-born, New Orleans photographer Theodore Lilienthal successfully sought legal redress in an 1881 infringement case involving his "Lambert Process" in the Eastern District of Louisiana.
[edit] Popularization
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).
A photographer appears to be photographing himself in a 19th-century photographic studio. (c.?1893)
The daguerreotype proved popular in responding to the demand for portraiture emerging from the middle classes during the Industrial Revolution.[citation needed] This demand, that could not be met in volume and in cost by oil painting, added to the push for the development of photography. By 1851 a broadside by daguerreotypist Augustus Washington was advertising prices ranging from 50 cents to $10.[11] However, daguerreotypes were fragile and difficult to copy. Photographers encouraged chemists to refine the process of making many copies cheaply, which eventually led them back to Talbot's process.
Ultimately, the modern photographic process came about from a series of refinements and improvements in the first 20 years. In 1884 George Eastman, of Rochester, New York, developed dry gel on paper, or film, to replace the photographic plate so that a photographer no longer needed to carry boxes of plates and toxic chemicals around. In July 1888 Eastman's Kodak camera went on the market with the slogan "You press the button, we do the rest". Now anyone could take a photograph and leave the complex parts of the process to others, and photography became available for the mass-market in 1901 with the introduction of the Kodak Brownie.
In the twentieth century, photography developed rapidly as a commercial service. End-user supplies of photographic equipment accounted for only about 20 percent of industry revenue. For the modern enthusiast photographer processing black and white film, little has changed since the introduction of the 35mm film Leica camera in 1925.[citation needed]
[edit] Color process
First color image, photograph by James Maxwell, 1861.
Although color photography was explored throughout the 19th century, initial experiments in color resulted in projected temporary images, rather than permanent color images. Moreover until the 1870s the emulsions available were not sensitive to red or green light.
The first color photo, an additive projected image of a tartan ribbon, was taken in 1861 by the Scottish physicist James Clerk Maxwell.[12] Several patentable methods for producing images (by either additive or subtractive methods, see below) were devised from 1862 on by two French inventors (working independently), Louis Ducos du Hauron and Charles Cros.[13] Practical methods to sensitize silver halide film to green and then orange light were discovered in 1873 and 1884 by Hermann W. Vogel (full sensitivity to red light was not achieved until the early years of the 20th century).
The first fully practical color plate, Autochrome, did not reach the market until 1907. It was based on a screen-plate method, the screen (of filters) being made using dyed dots of potato starch. The screen lets filtered red, green or blue light through each grain to a photographic emulsion in contact with it. The plate is then developed to a negative, and reversed to a positive, which when viewed through the screen restores colors approximating the original.
Other systems of color photography included that used by Sergei Mikhailovich Prokudin-Gorskii, which involved three separate monochrome exposures ('separation negatives') of a still scene through red, green, and blue filters. These required a special machine to display, but the results are impressive even by modern standards. His collection of glass plates was purchased from his heirs by the Library of Congress in 1948, and is now available in digital images.
A camera obscura box used for drawing images
Photography is the result of combining several technical discoveries. Long before the first photographs were made, Chinese philosopher Mo Ti and Greek philosophers such as Aristotle and Euclid described a pinhole camera in the 5th and 4th centuries B.C.E,[2][3] Ibn al-Haytham (Alhazen) (965–1040) studied the camera obscura and pinhole camera,[3][4] Albertus Magnus (1193/1206-1280) discovered silver nitrate, and Georges Fabricius (1516-1571) discovered silver chloride. Daniel Barbaro described a diaphragm in 1568. Wilhelm Homberg described how light darkened some chemicals (photochemical effect) in 1694. The novel Giphantie (by the French Tiphaigne de la Roche, 1729-1774) described what can be interpreted as photography.
For years images have been projected onto surfaces. According to the Hockney–Falco thesis as argued by artist David Hockney,[5] some artists used the camera obscura and camera lucida to trace scenes as early as the 16th century. However, this theory is heavily disputed by today's contemporary realist artists who are able to create high levels of realism without optical aids.[6] These early cameras did not record an image, but only projected images from an opening in the wall of a darkened room onto a surface, turning the room into a large pinhole camera. The phrase camera obscura literally means dark chamber. While this early prototype of today's modern camera may have had modest usage in its time, it was an important step in the evolution of the invention.
Nicéphore Niépce's earliest surviving photograph of a scene from nature, circa 1826, "View from the Window at Le Gras," Saint-Loup-de-Varennes (France).
"Boulevard du Temple", taken by Louis Daguerre in late 1838 or early 1839, was the first-ever photograph of a person. It is an image of a busy street, but because exposure time was over ten minutes, the city traffic was moving too much to appear. The exception is a man in the bottom left corner, who stood still getting his boots polished long enough to show up in the picture.
Robert Cornelius, self-portrait, Oct. or Nov. 1839, approximate quarter plate daguerreotype. The back reads, "The first light picture ever taken." This self-portrait is the first photographic portrait image of a human ever produced.
The first permanent photograph was an image produced in 1825 by the French inventor Joseph Nicéphore Niépce. His photographs were produced on a polished pewter plate covered with a petroleum derivative called bitumen of Judea. Bitumen hardens with exposure to light. The unhardened material may then be washed away and the metal plate polished, rendering a negative image which then may be coated with ink and impressed upon paper, producing a print. Niépce then began experimenting with silver compounds based on a Johann Heinrich Schultz discovery in 1724 that a silver and chalk mixture darkens when exposed to light.
In partnership, Niépce (in Chalon-sur-Saône) and Louis Daguerre (in Paris) refined the existing silver process.[7] In 1833 Niépce died of a stroke, leaving his notes to Daguerre. While he had no scientific background, Daguerre made two pivotal contributions to the process. He discovered that exposing the silver first to iodine vapour before exposure to light, and then to mercury fumes after the photograph was taken, could form a latent image. Bathing the plate in a salt bath then fixes the image. On January 7, 1839 Daguerre announced that he had invented a process using silver on a copper plate called the daguerreotype.[8] The French government bought the patent and immediately made it public domain.
In 1832, French-Brazilian painter and inventor Hercules Florence had already created a very similar process, naming it Photographie.
After reading about Daguerre's invention, Fox Talbot worked on perfecting his own process; in 1839 he got a key improvement, an effective fixer, from John Herschel, the astronomer, who had previously showed that hyposulfite of soda (also known as hypo, or now sodium thiosulfate) would dissolve silver salts. Later that year, Herschel made the first glass negative.
By 1840, Talbot had invented the calotype process. He coated paper sheets with silver chloride to create an intermediate negative image. Unlike a daguerreotype, a calotype negative could be used to reproduce positive prints, like most chemical films do today. Talbot patented[9] this process, which greatly limited its adoption. He spent the rest of his life in lawsuits defending the patent until he gave up on photography. Later George Eastman refined Talbot's process, which is the basic technology used by chemical film cameras today. Hippolyte Bayard had also developed a method of photography but delayed announcing it, and so was not recognized as its inventor.
In 1851 Frederick Scott Archer invented the collodion process.[citation needed] Photographer and children's author Lewis Carroll used this process.[citation needed]
Roger Fenton's assistant seated on Fenton's photographic van, Crimea, 1855.
Slovene Janez Puhar invented the technical procedure for making photographs on glass in 1841.[citation needed] The invention was recognized on July 17, 1852 in Paris by the Académie Nationale Agricole, Manufacturière et Commerciale.
Herbert Bowyer Berkeley experimented with his own version of collodian emulsions after Samman introduced the idea of adding dithionite to the pyrogallol developer.[citation needed] Berkeley discovered that with his own addition of sulfite, to absorb the sulfur dioxide given off by the chemical dithionite in the developer, that dithionite was not required in the developing process. In 1881 he published his discovery. Berkeley's formula contained pyrogallol, sulfite and citric acid. Ammonia was added just before use to make the formula alkaline. The new formula was sold by the Platinotype Company in London as Sulpho-Pyrogallol Developer.[10]
Nineteenth-century experimentation with photographic processes frequently became proprietary. The German-born, New Orleans photographer Theodore Lilienthal successfully sought legal redress in an 1881 infringement case involving his "Lambert Process" in the Eastern District of Louisiana.
[edit] Popularization
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).
A photographer appears to be photographing himself in a 19th-century photographic studio. (c.?1893)
The daguerreotype proved popular in responding to the demand for portraiture emerging from the middle classes during the Industrial Revolution.[citation needed] This demand, that could not be met in volume and in cost by oil painting, added to the push for the development of photography. By 1851 a broadside by daguerreotypist Augustus Washington was advertising prices ranging from 50 cents to $10.[11] However, daguerreotypes were fragile and difficult to copy. Photographers encouraged chemists to refine the process of making many copies cheaply, which eventually led them back to Talbot's process.
Ultimately, the modern photographic process came about from a series of refinements and improvements in the first 20 years. In 1884 George Eastman, of Rochester, New York, developed dry gel on paper, or film, to replace the photographic plate so that a photographer no longer needed to carry boxes of plates and toxic chemicals around. In July 1888 Eastman's Kodak camera went on the market with the slogan "You press the button, we do the rest". Now anyone could take a photograph and leave the complex parts of the process to others, and photography became available for the mass-market in 1901 with the introduction of the Kodak Brownie.
In the twentieth century, photography developed rapidly as a commercial service. End-user supplies of photographic equipment accounted for only about 20 percent of industry revenue. For the modern enthusiast photographer processing black and white film, little has changed since the introduction of the 35mm film Leica camera in 1925.[citation needed]
[edit] Color process
First color image, photograph by James Maxwell, 1861.
Although color photography was explored throughout the 19th century, initial experiments in color resulted in projected temporary images, rather than permanent color images. Moreover until the 1870s the emulsions available were not sensitive to red or green light.
The first color photo, an additive projected image of a tartan ribbon, was taken in 1861 by the Scottish physicist James Clerk Maxwell.[12] Several patentable methods for producing images (by either additive or subtractive methods, see below) were devised from 1862 on by two French inventors (working independently), Louis Ducos du Hauron and Charles Cros.[13] Practical methods to sensitize silver halide film to green and then orange light were discovered in 1873 and 1884 by Hermann W. Vogel (full sensitivity to red light was not achieved until the early years of the 20th century).
The first fully practical color plate, Autochrome, did not reach the market until 1907. It was based on a screen-plate method, the screen (of filters) being made using dyed dots of potato starch. The screen lets filtered red, green or blue light through each grain to a photographic emulsion in contact with it. The plate is then developed to a negative, and reversed to a positive, which when viewed through the screen restores colors approximating the original.
Other systems of color photography included that used by Sergei Mikhailovich Prokudin-Gorskii, which involved three separate monochrome exposures ('separation negatives') of a still scene through red, green, and blue filters. These required a special machine to display, but the results are impressive even by modern standards. His collection of glass plates was purchased from his heirs by the Library of Congress in 1948, and is now available in digital images.
mercoledì 2 dicembre 2009
High speed photography
High speed photography is the science of taking pictures of very fast phenomena. In 1948, the Society of Motion Picture and Television Engineers (SMPTE) defined high-speed photography as any set of photographs captured by a camera capable of 128 frames per second or greater, and of at least three consecutive frames. High speed photography can be considered to be the opposite of time-lapse photography.
In common usage, high speed photography may refer to either or both of the following meanings. The first is that the photograph itself may be taken in a way as to appear to freeze the motion, especially to reduce motion blur. The second is that a series of photographs may be taken at a high sampling frequency or frame rate. The first requires a sensor with good sensitivity and either a very good shuttering system or a very fast strobe light. The second requires some means of capturing successive frames, either with a mechanical device or by moving data off electronic sensors very quickly.
Other considerations for high-speed photographers are record length, reciprocity breakdown, and spatial resolution
High speed motion pictures started in 1916 by German weapons scientists [7] .
Methods developed using stationary medium with frames in turn activated by a rotating mirror to rotating prism cameras using fast moving film [8] .
As film and mechanical transports improved, the high-speed film camera became available for scientific research. Kodak eventually shifted its film from acetate base to Estar (Kodak's name for a Mylar-equivalent plastic), which enhanced the strength and allowed it to be pulled faster. The Estar was also more stable than acetate allowing more accurate measurement, and it was not as prone to fire.
Each film type is available in many load sizes. These may be cut down and placed in magazines for easier loading. A 1,200-foot (370 m) magazine is typically the longest available for the 35 mm and 70 mm cameras. A 400-foot (120 m) magazine is typical for 16 mm cameras, though 1,000-foot (300 m) magazines are available. Typically rotary prism cameras use 100ft (30m) film loads. The images on 35 mm high-speed film are typically rectangular with the long side between the sprocket holes instead of parallel to the edges as in standard photography. 16 mm and 70 mm images are typically square rather than rectangular. A list of ANSI formats and sizes is available[9][10].
Most cameras use pulsed timing marks along the edge of the film (either inside or outside of the film perforations) produced by sparks or later by LEDs. These allow accurate measurement of the film speed and in the case of streak or smear images, velocity measurement of the subject. These pulses are usually cycled at 10, 100, 1000 Hz depending on the speed setting of the camera.
For the development of explosives the image of a line of sample was projected onto an arc of film via a rotating mirror. The advance of flame appeared as an oblique image on the film, from which the velocity of detonation was measured [12] .
By removing the prism from the rotary prism cameras and using a very narrow slit in place of the shutter, it is possible to take images whose exposure is proportional to the film speed across the slit. The image that results has several useful properties. The film advance direction is essentially a measure of time. If the subject's motion is perpendicular to the slit, it may show growth or motion perpendicular to the slit.
Motion compensation photography (also known as Ballistic Syncro Photography or Smear Photography when used to image high speed projectiles) is a form of streak photography. When the motion of the film is opposite to that of the subject with an inverting (positive) lens, and synchronized appropriately, the images show events as a function of time. Objects remaining motionless show up as streaks. This is the technique used for finish line photographs. At no time is it possible to take a still photograph that duplicates the results of a finish line photograph taken with this method. A still is a photograph in time, a streak/smear photograph is a photograph of time. When used to image high speed projectiles the use of a slit (as in Streak Photography) produce very short exposure times ensuring higher image resolution. The use for high speed projectiles means that one still image is normally produced on one roll of cine film. From this image information such as yaw or pitch can be determined. Because of its measurement of time variations in velocity will also be shown by lateral distortions of the image.
By combining this technique with a diffracted wavefront of light, as by a knife-edge, it is possible to take photographs of phase perturbations within a homogeneous medium. For example, it is possible to capture shockwaves of bullets and other high-speed objects. See, for example, Shadowgraph and Schlieren photography.
[edit] Video
In common usage, high speed photography may refer to either or both of the following meanings. The first is that the photograph itself may be taken in a way as to appear to freeze the motion, especially to reduce motion blur. The second is that a series of photographs may be taken at a high sampling frequency or frame rate. The first requires a sensor with good sensitivity and either a very good shuttering system or a very fast strobe light. The second requires some means of capturing successive frames, either with a mechanical device or by moving data off electronic sensors very quickly.
Other considerations for high-speed photographers are record length, reciprocity breakdown, and spatial resolution
High speed motion pictures started in 1916 by German weapons scientists [7] .
Methods developed using stationary medium with frames in turn activated by a rotating mirror to rotating prism cameras using fast moving film [8] .
As film and mechanical transports improved, the high-speed film camera became available for scientific research. Kodak eventually shifted its film from acetate base to Estar (Kodak's name for a Mylar-equivalent plastic), which enhanced the strength and allowed it to be pulled faster. The Estar was also more stable than acetate allowing more accurate measurement, and it was not as prone to fire.
Each film type is available in many load sizes. These may be cut down and placed in magazines for easier loading. A 1,200-foot (370 m) magazine is typically the longest available for the 35 mm and 70 mm cameras. A 400-foot (120 m) magazine is typical for 16 mm cameras, though 1,000-foot (300 m) magazines are available. Typically rotary prism cameras use 100ft (30m) film loads. The images on 35 mm high-speed film are typically rectangular with the long side between the sprocket holes instead of parallel to the edges as in standard photography. 16 mm and 70 mm images are typically square rather than rectangular. A list of ANSI formats and sizes is available[9][10].
Most cameras use pulsed timing marks along the edge of the film (either inside or outside of the film perforations) produced by sparks or later by LEDs. These allow accurate measurement of the film speed and in the case of streak or smear images, velocity measurement of the subject. These pulses are usually cycled at 10, 100, 1000 Hz depending on the speed setting of the camera.
For the development of explosives the image of a line of sample was projected onto an arc of film via a rotating mirror. The advance of flame appeared as an oblique image on the film, from which the velocity of detonation was measured [12] .
By removing the prism from the rotary prism cameras and using a very narrow slit in place of the shutter, it is possible to take images whose exposure is proportional to the film speed across the slit. The image that results has several useful properties. The film advance direction is essentially a measure of time. If the subject's motion is perpendicular to the slit, it may show growth or motion perpendicular to the slit.
Motion compensation photography (also known as Ballistic Syncro Photography or Smear Photography when used to image high speed projectiles) is a form of streak photography. When the motion of the film is opposite to that of the subject with an inverting (positive) lens, and synchronized appropriately, the images show events as a function of time. Objects remaining motionless show up as streaks. This is the technique used for finish line photographs. At no time is it possible to take a still photograph that duplicates the results of a finish line photograph taken with this method. A still is a photograph in time, a streak/smear photograph is a photograph of time. When used to image high speed projectiles the use of a slit (as in Streak Photography) produce very short exposure times ensuring higher image resolution. The use for high speed projectiles means that one still image is normally produced on one roll of cine film. From this image information such as yaw or pitch can be determined. Because of its measurement of time variations in velocity will also be shown by lateral distortions of the image.
By combining this technique with a diffracted wavefront of light, as by a knife-edge, it is possible to take photographs of phase perturbations within a homogeneous medium. For example, it is possible to capture shockwaves of bullets and other high-speed objects. See, for example, Shadowgraph and Schlieren photography.
[edit] Video
Gray card
A gray card is a middle gray reference, typically used together with a reflective light meter, as a way to produce consistent image exposure and/or color in film and photography.
A gray card is a flat object of a neutral gray color that derives from a flat reflectance spectrum. A typical examples is the Kodak R-27 set, which contains two 8x10" cards and one 4x5" card which have 18% reflectance across the visible spectrum, and a white reverse side which has 90% reflectance. Note that flat spectral reflectance is a stronger condition than simply appearing neutral; this flatness ensures that the card appears neutral under any illuminant (see metamerism).
A major use of gray cards is to provide a standard reference object for exposure determination in photography. A gray card is an (approximate) realisation of a Lambertian scatterer; its apparent brightness (and exposure determination) therefore does not depend on its orientation relative to the light source. By placing a gray card in the scene to be photographed, oriented at a defined angle relative to the direction of the incident light, and taking a reading from it with a reflected light meter, the photographer can be assured of consistent exposures across their photographs. This technique is similar to using an incident meter, as it depends on the illuminance but not the reflectivity of the subject.
In addition to providing a means for measuring exposure, a gray card provides a convenient reference for white balance, or color balance, allowing the camera to compensate for the illuminant color in a scene.
Gray cards can be used for in-camera white balance or post-processing white balance. Many digital cameras have a custom white balance feature. A photo of the gray card is taken and used to set white balace for a sequence of photos. For post-processing white balance, a photo of the gray card in the scene is taken, and the image processing software uses the data from the pixels in the gray card area of the photo to set the white balance point for the whole image.
Most digital cameras do a reasonable job of controlling color. For the casual user, a gray card is unnecessary. Many serious photographers or hobbyists consider gray cards an essential part of the digital photography process.
Gray cards are made of a variety of materials including plastic, paper, and foam. Some photographers hold[citation needed] that any neutral white or grey surface, such as a white piece of paper, a concrete or stone wall, or a white shirt are suitable substitutes for a gray card; however, since bright white papers and clothing washed in typical detergents contain fluorescent whitening agents, they tend to not be very spectrally neutral.[1] Gray cards specially made to be spectrally flat are therefore more suitable to the purpose than surfaces that happen to be available.
A gray card is a flat object of a neutral gray color that derives from a flat reflectance spectrum. A typical examples is the Kodak R-27 set, which contains two 8x10" cards and one 4x5" card which have 18% reflectance across the visible spectrum, and a white reverse side which has 90% reflectance. Note that flat spectral reflectance is a stronger condition than simply appearing neutral; this flatness ensures that the card appears neutral under any illuminant (see metamerism).
A major use of gray cards is to provide a standard reference object for exposure determination in photography. A gray card is an (approximate) realisation of a Lambertian scatterer; its apparent brightness (and exposure determination) therefore does not depend on its orientation relative to the light source. By placing a gray card in the scene to be photographed, oriented at a defined angle relative to the direction of the incident light, and taking a reading from it with a reflected light meter, the photographer can be assured of consistent exposures across their photographs. This technique is similar to using an incident meter, as it depends on the illuminance but not the reflectivity of the subject.
In addition to providing a means for measuring exposure, a gray card provides a convenient reference for white balance, or color balance, allowing the camera to compensate for the illuminant color in a scene.
Gray cards can be used for in-camera white balance or post-processing white balance. Many digital cameras have a custom white balance feature. A photo of the gray card is taken and used to set white balace for a sequence of photos. For post-processing white balance, a photo of the gray card in the scene is taken, and the image processing software uses the data from the pixels in the gray card area of the photo to set the white balance point for the whole image.
Most digital cameras do a reasonable job of controlling color. For the casual user, a gray card is unnecessary. Many serious photographers or hobbyists consider gray cards an essential part of the digital photography process.
Gray cards are made of a variety of materials including plastic, paper, and foam. Some photographers hold[citation needed] that any neutral white or grey surface, such as a white piece of paper, a concrete or stone wall, or a white shirt are suitable substitutes for a gray card; however, since bright white papers and clothing washed in typical detergents contain fluorescent whitening agents, they tend to not be very spectrally neutral.[1] Gray cards specially made to be spectrally flat are therefore more suitable to the purpose than surfaces that happen to be available.
Portrait photography
Portrait photography or portraiture is the capture by means of photography of the likeness of a person or a small group of people (a group portrait), in which the face and expression is predominant. The objective is to display the likeness, personality, and even the mood of the subject. Like other types of portraiture, the focus of the photograph is the person's face, although the entire body and the background may be included. A portrait is generally not a snapshot, but a composed image of a person in a still position. A portrait often shows a person looking directly at the camera.
Unlike many other photography styles, the subjects of portrait photography are often non-professional models. Family portraits commemorating special occasions, such as graduations or weddings, may be professionally produced or may be vernacular and are most often intended for private viewing rather than for public exhibition.
However, many portraits are created for public display ranging from fine art portraiture, to commercial portraiture such as might be used to illustrate a company's annual report, to promotional portraiture such a might be found on a book jacket showing the author of the book.
Portrait photography has been around since the invention and popularization of the camera. It is a cheaper and often more accessible method than portrait painting, which has been used by distinguished figures before the popularity of the camera.
The relatively low cost of the daguerreotype in the middle of the 19th century lead to its popularity for portraiture. Studios sprang up in cities around the world, some producing more than 500 plates a day. The style of these early works reflected the technical challenges associated with 30-second exposure times and the painterly aesthetic of the time. Subjects were generally seated against plain backgrounds and lit with the soft light of an overhead window and whatever else could be reflected with mirrors. As the equipment became more advanced, the ability to capture images with short exposure times gave photographer more creative freedom and thus created new styles of portrait photography.
As photographic techniques developed, photographers took their talents out of the studio and onto battlefields, across oceans and into remote wilderness. William Shew's Daguerreotype Saloon, Roger Fenton's Photographic Van and Mathew Brady's What-is-it? wagon set the standards for making portraits and other photographs in the field.
[edit] Lighting for portraiture
When portrait photographs are composed and captured in a studio, the professional photographer has control over the lighting of the composition of the subject and can adjust direction and intensity. There are many ways to light a subject's face, but there are several common lighting plans which are easy enough to describe. Of course making them work in a studio or on location is a matter of experimentation and practice.
[edit] Three-Point Lighting
One of the most basic lighting plans is called three-point lighting. This plan uses three (and sometimes four) lights to fully model (bring out details and the three-dimensionality of) the subject's features. The three main lights used in this light plan are as follows:
[edit] The Key light
Also called a main light, the key light is usually placed to one side of the subject's face, between 30 and 60 degrees off centre and a bit higher than eye level. The key light is the brightest light in the lighting plan.
[edit] The Fill light
Placed opposite the key light, the fill light fills in or softens the shadows on the opposite side of the face. The brightness of the fill light is usually between 1/3 and 1/4 that of the key light. This is expressed as a ratio as in 3:1 or 4:1. When the ratio is 3:1 this is sometimes called Kodak lighting since this was the ratio suggested by Kodak in the instructional booklets accompanying the company's early cameras.
The purpose of these two lights is to mimic the natural light created by placing a subject in a room near a window. The daylight falling on the subject through the window is the Key light and the Fill light is reflected light coming from the walls of the room. This type of lighting can be found in the works of hundreds of classical painters and early photographers and is often called Rembrandt lighting.
Modern portraitists have chosen to add one or two lights to this lighting plan.
[edit] The Rim light
Also called a backlight or hair light, the rim light (the third main light in the three-point lighting plan) is placed behind the subject, out of the picture frame, and often rather higher than the Key light or Fill. The point of the rim light is to provide separation from the background by highlighting the subject's shoulders and hair. The rim light should be just bright enough to provide separation from the background, but not as bright as the key light.
[edit] Butterfly lighting
Butterfly lighting is another common lighting plan and has been very popular over the past decade or so. In this case, only two lights are common. The Key light is placed directly in front of the subject, often above the camera or slightly to one side, and a bit higher than is common for a three-point lighting plan. The second light is a rim light. Often a reflector is placed below the subject's face to provide fill light and soften shadows.
This lighting can be recognised by the strong light falling on the forehead, the bridge of the nose and the upper cheeks, and by the distinct shadow below the nose which often looks rather like a butterfly and thus provides the name for this lighting plan. Butterfly lighting was a favourite of famed Hollywood portraitist George Hurrell which is why this style of lighting is often called Paramount lighting, after the movie studio of the same name.
[edit] Accessory lights
These lights can be added to basic lighting plans to provide additional highlights or add background definition.
[edit] The Kicker
A kicker is a small light, often made directional through the use of a snoot, umbrella, or softbox. The kicker is designed to add highlights to the off side of the subject's face, usually just enough to establish the jaw line or edge of an ear. The kicker should thus be a bit brighter than the fill light, but not so bright it over fills the off side of the face. Many portraitists choose not to use a kicker and settle for the three main lights of the standard plans.
[edit] Background lights
Not so much a part of the portrait lighting plan, but rather designed to provide illumination for the background behind the subject, background lights can pick out details in the background, provide a halo effect by illuminating a portion of a backdrop behind the subject's head, or turn the background pure white by filling it with light.
[edit] Other lighting equipment
Most lights used in modern photography are a flash of some sort. The lighting for portraiture is typically diffused by bouncing it from the inside of an umbrella, or by using a soft box. A soft box is a fabric box, encasing a photo strobe head, one side of which is made of translucent fabric. This provides a softer lighting for portrait work and is often considered more appealing than the harsh light often cast by open strobes. Hair and background lights are usually not diffused. It is more important to control light spillage to other areas of the subject. Snoots, barn doors and flags or gobos help focus the lights exactly where the photographer wants them. Background lights are sometimes used with color gels placed in front of the light to create coloured backgrounds.
[edit] Styles of portraiture
There are many different techniques for portrait photography. Often it is desirable to capture the subject's eyes and face in sharp focus while allowing other less important elements to be rendered in a soft focus. At other times, portraits of individual features might be the focus of a composition such as the hands, eyes or part of the subject's torso.
Unlike many other photography styles, the subjects of portrait photography are often non-professional models. Family portraits commemorating special occasions, such as graduations or weddings, may be professionally produced or may be vernacular and are most often intended for private viewing rather than for public exhibition.
However, many portraits are created for public display ranging from fine art portraiture, to commercial portraiture such as might be used to illustrate a company's annual report, to promotional portraiture such a might be found on a book jacket showing the author of the book.
Portrait photography has been around since the invention and popularization of the camera. It is a cheaper and often more accessible method than portrait painting, which has been used by distinguished figures before the popularity of the camera.
The relatively low cost of the daguerreotype in the middle of the 19th century lead to its popularity for portraiture. Studios sprang up in cities around the world, some producing more than 500 plates a day. The style of these early works reflected the technical challenges associated with 30-second exposure times and the painterly aesthetic of the time. Subjects were generally seated against plain backgrounds and lit with the soft light of an overhead window and whatever else could be reflected with mirrors. As the equipment became more advanced, the ability to capture images with short exposure times gave photographer more creative freedom and thus created new styles of portrait photography.
As photographic techniques developed, photographers took their talents out of the studio and onto battlefields, across oceans and into remote wilderness. William Shew's Daguerreotype Saloon, Roger Fenton's Photographic Van and Mathew Brady's What-is-it? wagon set the standards for making portraits and other photographs in the field.
[edit] Lighting for portraiture
When portrait photographs are composed and captured in a studio, the professional photographer has control over the lighting of the composition of the subject and can adjust direction and intensity. There are many ways to light a subject's face, but there are several common lighting plans which are easy enough to describe. Of course making them work in a studio or on location is a matter of experimentation and practice.
[edit] Three-Point Lighting
One of the most basic lighting plans is called three-point lighting. This plan uses three (and sometimes four) lights to fully model (bring out details and the three-dimensionality of) the subject's features. The three main lights used in this light plan are as follows:
[edit] The Key light
Also called a main light, the key light is usually placed to one side of the subject's face, between 30 and 60 degrees off centre and a bit higher than eye level. The key light is the brightest light in the lighting plan.
[edit] The Fill light
Placed opposite the key light, the fill light fills in or softens the shadows on the opposite side of the face. The brightness of the fill light is usually between 1/3 and 1/4 that of the key light. This is expressed as a ratio as in 3:1 or 4:1. When the ratio is 3:1 this is sometimes called Kodak lighting since this was the ratio suggested by Kodak in the instructional booklets accompanying the company's early cameras.
The purpose of these two lights is to mimic the natural light created by placing a subject in a room near a window. The daylight falling on the subject through the window is the Key light and the Fill light is reflected light coming from the walls of the room. This type of lighting can be found in the works of hundreds of classical painters and early photographers and is often called Rembrandt lighting.
Modern portraitists have chosen to add one or two lights to this lighting plan.
[edit] The Rim light
Also called a backlight or hair light, the rim light (the third main light in the three-point lighting plan) is placed behind the subject, out of the picture frame, and often rather higher than the Key light or Fill. The point of the rim light is to provide separation from the background by highlighting the subject's shoulders and hair. The rim light should be just bright enough to provide separation from the background, but not as bright as the key light.
[edit] Butterfly lighting
Butterfly lighting is another common lighting plan and has been very popular over the past decade or so. In this case, only two lights are common. The Key light is placed directly in front of the subject, often above the camera or slightly to one side, and a bit higher than is common for a three-point lighting plan. The second light is a rim light. Often a reflector is placed below the subject's face to provide fill light and soften shadows.
This lighting can be recognised by the strong light falling on the forehead, the bridge of the nose and the upper cheeks, and by the distinct shadow below the nose which often looks rather like a butterfly and thus provides the name for this lighting plan. Butterfly lighting was a favourite of famed Hollywood portraitist George Hurrell which is why this style of lighting is often called Paramount lighting, after the movie studio of the same name.
[edit] Accessory lights
These lights can be added to basic lighting plans to provide additional highlights or add background definition.
[edit] The Kicker
A kicker is a small light, often made directional through the use of a snoot, umbrella, or softbox. The kicker is designed to add highlights to the off side of the subject's face, usually just enough to establish the jaw line or edge of an ear. The kicker should thus be a bit brighter than the fill light, but not so bright it over fills the off side of the face. Many portraitists choose not to use a kicker and settle for the three main lights of the standard plans.
[edit] Background lights
Not so much a part of the portrait lighting plan, but rather designed to provide illumination for the background behind the subject, background lights can pick out details in the background, provide a halo effect by illuminating a portion of a backdrop behind the subject's head, or turn the background pure white by filling it with light.
[edit] Other lighting equipment
Most lights used in modern photography are a flash of some sort. The lighting for portraiture is typically diffused by bouncing it from the inside of an umbrella, or by using a soft box. A soft box is a fabric box, encasing a photo strobe head, one side of which is made of translucent fabric. This provides a softer lighting for portrait work and is often considered more appealing than the harsh light often cast by open strobes. Hair and background lights are usually not diffused. It is more important to control light spillage to other areas of the subject. Snoots, barn doors and flags or gobos help focus the lights exactly where the photographer wants them. Background lights are sometimes used with color gels placed in front of the light to create coloured backgrounds.
[edit] Styles of portraiture
There are many different techniques for portrait photography. Often it is desirable to capture the subject's eyes and face in sharp focus while allowing other less important elements to be rendered in a soft focus. At other times, portraits of individual features might be the focus of a composition such as the hands, eyes or part of the subject's torso.
Night photography
Night photography refers to photographs taken outdoors between dusk and dawn. Night photographers generally have a choice between using artificial light or using a long exposure, exposing the scene for seconds or even minutes, in order to give the film enough time to capture a usable image, and to compensate for reciprocity failure. With the progress of high-speed films, higher-sensitivity digital image sensors, wide-aperture lenses, and the ever-greater power of urban lights, night photography is increasingly possible using available light.
In the early 1900s, a few notable photographers, Alfred Stieglitz and William Fraser, began working at night. The first photographers known to have produced large bodies of work at night were Brassai and Bill Brandt. In 1932, Brassai published Paris de Nuit, a book of black-and-white photographs of the streets of Paris at night. During World War II, British photographer Brandt took advantage of the black-out conditions to photograph the streets of London by moonlight.
By the 1990s, British-born photographer Michael Kenna had established himself as the most commercially successful night photographer. His black-and-white landscapes were most often set between dusk and dawn in locations that included San Francisco, Japan, France, and England. Some of his most memorable projects depict the Ford Motor Company's Rogue River plant, the Ratcliffe-on-Soar Power Station in northern England, and many of the Nazi concentration camps scattered across Germany, France, Belgium, Poland and Austria.
During the beginning of the 21st century, the popularity of digital cameras made it much easier for beginning photographers to understand the complexities of photographing at night. Today, there are hundreds of websites dedicated to night photography.
In the early 1900s, a few notable photographers, Alfred Stieglitz and William Fraser, began working at night. The first photographers known to have produced large bodies of work at night were Brassai and Bill Brandt. In 1932, Brassai published Paris de Nuit, a book of black-and-white photographs of the streets of Paris at night. During World War II, British photographer Brandt took advantage of the black-out conditions to photograph the streets of London by moonlight.
By the 1990s, British-born photographer Michael Kenna had established himself as the most commercially successful night photographer. His black-and-white landscapes were most often set between dusk and dawn in locations that included San Francisco, Japan, France, and England. Some of his most memorable projects depict the Ford Motor Company's Rogue River plant, the Ratcliffe-on-Soar Power Station in northern England, and many of the Nazi concentration camps scattered across Germany, France, Belgium, Poland and Austria.
During the beginning of the 21st century, the popularity of digital cameras made it much easier for beginning photographers to understand the complexities of photographing at night. Today, there are hundreds of websites dedicated to night photography.
Monochrome photography
Monochrome photography is the recording of single colour, or wavelength, of light. The term generally refers to all forms of black and white photography, recording light in tones of grey ranging from black to white.[1]
Black and white photography is considered more subtle and interpretive, and less realistic than colour photography.[1] Monochrome images are not direct renditions of their subjects, but are abstractions from reality, representing colors in shades of grey. In computer terms, this is often called greyscale.[citation needed]
Monochrome images may be produced using black and white film or paper or by manipulating colour images using computer software.
Black and white photography is considered more subtle and interpretive, and less realistic than colour photography.[1] Monochrome images are not direct renditions of their subjects, but are abstractions from reality, representing colors in shades of grey. In computer terms, this is often called greyscale.[citation needed]
Monochrome images may be produced using black and white film or paper or by manipulating colour images using computer software.
Iscriviti a:
Post (Atom)