The camera obscura (Lat. dark chamber) was an optical device used in drawing, and one of the ancestral threads leading to the invention of photography. In English, today's photographic devices are still known as "cameras".
The principle of the camera obscura can be demonstrated with a rudimentary type, just a box (which may be room-size) with a hole in one side, (see pinhole camera for construction details). Light from only one part of a scene will pass through the hole and strike a specific part of the back wall. The projection is made on paper on which an artist can then copy the image. The advantage of this technique is that the perspective is right, thus greatly increasing the realism of the image (correct perspective in drawing can also be achieved by looking through a wire mesh and copying the view onto a canvas with a corresponding grid on it).
With this simple do-it-yourself apparatus, the image is always upside-down. By using mirrors, as in the 18th century overhead version illustrated in the Discovery and Origins section, it is also possible to project an up-side-up image. Another more portable type, is a box with an angled mirror projecting onto tracing paper placed on the glass top, the image upright as viewed from the back.
As a pinhole is made smaller, the image gets sharper, but the light-sensitivity decreases. With too small a pinhole the sharpness again becomes worse due to diffraction. Practical camerae obscurae use a lens rather than a pinhole because it allows a larger aperture, giving a usable brightness while maintaining focus.
Monday, October 15, 2007
Composition
n the visual arts, in particular painting, graphic design, and photography and sculpture composition is the plan, placement or arrangement of elements or ingredients in an art work. The selection and placement of elements within the work contributes to a response from the viewer, the work of art is said to be aesthetically pleasing to the eye if the elements within the work are arranged in a balanced compositional way (Dunstan, 1979). However there are artists who sole aim is to disrupt traditional composition and challenge the viewer to rethink balance and design elements within art works, for instance artists like Salvador Dali.
Basically the term composition means 'putting together', any work of art from music to writing is arranged or put together using conscious thought. The various elements in the overall design usually relate to each other and to the whole art work (Dunstan, p. 7, 1979). There are fundamentally two types of composition: informal, and the less frequently found formal or symmetrical. Composition is also related to artistic canon, for example, the draughting of a pleasing face. In graphic design and desktop publishing, composition is commonly referred to as page layout.
Basically the term composition means 'putting together', any work of art from music to writing is arranged or put together using conscious thought. The various elements in the overall design usually relate to each other and to the whole art work (Dunstan, p. 7, 1979). There are fundamentally two types of composition: informal, and the less frequently found formal or symmetrical. Composition is also related to artistic canon, for example, the draughting of a pleasing face. In graphic design and desktop publishing, composition is commonly referred to as page layout.
Gelatin-silver process
The gelatin-silver process is the photographic process used with currently available black-and-white films and printing papers. A suspension of silver salts in gelatin is coated onto acetate film or fiber-based or resin coated paper and allowed to dry (hence the term dry plate). These materials remain stable for months and years unlike the 'wet plate' materials that preceded them.
The Gelatin-Silver process was introduced by R. L. Maddox in 1871 with subsequent considerable improvements in sensitivity obtained by Charles Harper Bennet in 1878. Intense research in the last 125 years has led to current materials that exhibit low grain and high sensitivity to light.
When small crystals (called grains) of silver salts such as silver bromide and silver chloride are exposed to light, a few atoms of free metallic silver are liberated. These free silver atoms form the latent image. This latent image is relatively stable and will persist for some months without degradation provided the film is kept dark and cool. Films are developed using solutions that reduce the free silver atoms. An 'amplification' of the latent image occurs as the silver salts near the free silver atom are also reduced to metallic silver. The strength, temperature and time for which the developer is allowed to act allow the photographer to control the contrast of the final image. The development is then stopped by neutralizing the developer in a second bath.
Once development is complete, the undeveloped silver salts must be removed by fixing in sodium thiosulphate or ammonium thiosulphate, and then the film or paper must be washed in clean water. The final image consists of metallic silver embedded in the gelatin coating.
See photographic processes for older methods that have seen something of a come-back recently amongst art photographers.
The Gelatin-Silver process was introduced by R. L. Maddox in 1871 with subsequent considerable improvements in sensitivity obtained by Charles Harper Bennet in 1878. Intense research in the last 125 years has led to current materials that exhibit low grain and high sensitivity to light.
When small crystals (called grains) of silver salts such as silver bromide and silver chloride are exposed to light, a few atoms of free metallic silver are liberated. These free silver atoms form the latent image. This latent image is relatively stable and will persist for some months without degradation provided the film is kept dark and cool. Films are developed using solutions that reduce the free silver atoms. An 'amplification' of the latent image occurs as the silver salts near the free silver atom are also reduced to metallic silver. The strength, temperature and time for which the developer is allowed to act allow the photographer to control the contrast of the final image. The development is then stopped by neutralizing the developer in a second bath.
Once development is complete, the undeveloped silver salts must be removed by fixing in sodium thiosulphate or ammonium thiosulphate, and then the film or paper must be washed in clean water. The final image consists of metallic silver embedded in the gelatin coating.
See photographic processes for older methods that have seen something of a come-back recently amongst art photographers.
Gum printing
Gum printing is a way of making photographic reproductions without the use of silver halides. The process used salts of dichromate in common with a number of other related procceses such as sun printing.
When mixtures of mucilaginous, protein-containing materials together with soluble salts of dichromate are exposed to ultraviolet light, the protein content becomes tanned and resistant to solution in water. The untanned material can be washed away in warm water leaving a hardened, tanned protein negative.
Gum printing using a solution of gum arabic mixed with either potassium or ammonium dichromate. The higher the proportion of dichromate, the more sensitive the mixture. However, increasing the concentration of dichromate also reduces the contrast which is very low at best. The right concentration of dichromate is always a compromise between speed and contrast.
Using ammonium dichromate allows concentrations up to 15% of the active ingredient whereas potassium dichromate is limited to about 10%. Exceeding these concentrations results in deposits of chromic acid in the dried film which ruins any attempts at printing. The greatest sensitivity expressed as an ASA rating is estimated to be about ASA 0.003.
In gum printing, the gum-dichromate mixture is supplemented by high quality powered pigment. The resulting mucilaginous mixture is spread on a suitable base and allowed to dry in the dark. A contact negative the same size of the finished print is then placed on top of the dried coating and exposed to an ultraviolet light source, typically bright sunshine.
Often more than one negative is used to provide detail in all tonal ranges. Using multiple exposures requires very careful registration.
In exposing the paper, the thinnest parts of the negatives will allow the most exposure and cause the areas to be darker. The densest parts of the negative, which require more exposure, will have less colour.
The exposed print is then developed gradually in a succession of trays of still water (approximately ten minute intervals) at room temperature until the bath water is clear. The gum is soft and easily removed at this stage. Gentle agitation with a soft bristled brush can be used to remove pigment in highlights, give a painterly brushed appearance, and to release extra pigment from over-exposed areas.
When mixtures of mucilaginous, protein-containing materials together with soluble salts of dichromate are exposed to ultraviolet light, the protein content becomes tanned and resistant to solution in water. The untanned material can be washed away in warm water leaving a hardened, tanned protein negative.
Gum printing using a solution of gum arabic mixed with either potassium or ammonium dichromate. The higher the proportion of dichromate, the more sensitive the mixture. However, increasing the concentration of dichromate also reduces the contrast which is very low at best. The right concentration of dichromate is always a compromise between speed and contrast.
Using ammonium dichromate allows concentrations up to 15% of the active ingredient whereas potassium dichromate is limited to about 10%. Exceeding these concentrations results in deposits of chromic acid in the dried film which ruins any attempts at printing. The greatest sensitivity expressed as an ASA rating is estimated to be about ASA 0.003.
In gum printing, the gum-dichromate mixture is supplemented by high quality powered pigment. The resulting mucilaginous mixture is spread on a suitable base and allowed to dry in the dark. A contact negative the same size of the finished print is then placed on top of the dried coating and exposed to an ultraviolet light source, typically bright sunshine.
Often more than one negative is used to provide detail in all tonal ranges. Using multiple exposures requires very careful registration.
In exposing the paper, the thinnest parts of the negatives will allow the most exposure and cause the areas to be darker. The densest parts of the negative, which require more exposure, will have less colour.
The exposed print is then developed gradually in a succession of trays of still water (approximately ten minute intervals) at room temperature until the bath water is clear. The gum is soft and easily removed at this stage. Gentle agitation with a soft bristled brush can be used to remove pigment in highlights, give a painterly brushed appearance, and to release extra pigment from over-exposed areas.
Hand-colouring
Hand-colouring refers to any of a number of methods of manually adding colour to a black-and-white photograph or other image to heighten its realism. Typically, water-colours, oils and other paints or dyes are applied to the image surface using brushes, fingers, cotton swabs or airbrushes. Some photographic genres, particularly landscapes and portraits, have been more often hand-coloured than others, and hand-coloured photographs have been popular enough that some firms specialised in producing them.
Holography
Holography was invented in 1947 by Hungarian physicist Dennis Gabor (1900–1979), work for which he received the Nobel Prize in physics in 1971. The discovery was an unexpected result of research into improving electron microscopes at the British Thomson-Houston Company in Rugby, England. The British Thomson-Houston company filed a patent on 1947-12-17 (and received patent GB685286), but the field did not really advance until the development of the laser in 1960.
The first holograms that recorded 3D objects were made by Emmett Leith and Juris Upatnieks in University of Michigan, USA in 1963 and Yuri Denisyuk in the Soviet Union.
Several types of hologram can be made. Transmission holograms, such as those produced by Leith and Upatnieks, are viewed by shining laser light through them and looking at the reconstructed image from the side of the hologram opposite the source. A later refinement, the "rainbow transmission" hologram allows more convenient illumination by white light rather than by lasers or other monochromatic sources. Rainbow holograms are commonly seen today on credit cards as a security feature and on product packaging. These versions of the rainbow transmission hologram are commonly formed as surface relief patterns in a plastic film, and they incorporate a reflective aluminium coating which provides the light from "behind" to reconstruct their imagery.
Another kind of common hologram, the reflection or Denisyuk hologram, is capable of multicolour image reproduction using a white light illumination source on the same side of the hologram as the viewer.
One of the most promising recent advances in the short history of holography has been the mass production of low-cost solid-state lasers - typically used by the millions in DVD recorders and other applications, but which are sometimes also useful for holography. These cheap, compact, solid-state lasers can under some circumstances compete well with the large, expensive gas lasers previously required to make holograms, and are already helping to make holography much more accessible to low-budget researchers, artists, and dedicated hobbyists.
The first holograms that recorded 3D objects were made by Emmett Leith and Juris Upatnieks in University of Michigan, USA in 1963 and Yuri Denisyuk in the Soviet Union.
Several types of hologram can be made. Transmission holograms, such as those produced by Leith and Upatnieks, are viewed by shining laser light through them and looking at the reconstructed image from the side of the hologram opposite the source. A later refinement, the "rainbow transmission" hologram allows more convenient illumination by white light rather than by lasers or other monochromatic sources. Rainbow holograms are commonly seen today on credit cards as a security feature and on product packaging. These versions of the rainbow transmission hologram are commonly formed as surface relief patterns in a plastic film, and they incorporate a reflective aluminium coating which provides the light from "behind" to reconstruct their imagery.
Another kind of common hologram, the reflection or Denisyuk hologram, is capable of multicolour image reproduction using a white light illumination source on the same side of the hologram as the viewer.
One of the most promising recent advances in the short history of holography has been the mass production of low-cost solid-state lasers - typically used by the millions in DVD recorders and other applications, but which are sometimes also useful for holography. These cheap, compact, solid-state lasers can under some circumstances compete well with the large, expensive gas lasers previously required to make holograms, and are already helping to make holography much more accessible to low-budget researchers, artists, and dedicated hobbyists.
Kirlian photography
Kirlian photography refers to a form of contact print photography, theoretically associated with high-voltage. It is named after Semyon Kirlian, who in 1939 accidentally discovered that if an object on a photographic plate is connected to a source of high voltage, small corona discharges (created by the strong electric field at the edges of the object) create an image on photographic plate.
Kirlian photography is completely different from "Aura photography," in which a colorful image is produced of a persons face and upper torso, using various methods of biofeedback. People commonly use the term "Kirlian photography" to erroneously refer to "Aura photography," and vice-versa. The terms have almost become interchangeable, even though the techniques are completely different. This leads to confusion among those who not familiar with the two different techniques. The Kirlian technique is contact photography, in which the subject is in direct contact with the film which is placed upon a metal plate that is charged with high voltage, high frequency electricity. In Aura Photography, no high voltage is involved as with the Kirlian technique, and no direct contact with the film is made. The images made with an Aura camera do not result from coronal discharge, the colors are projected with fiber optics.
Kirlian's work, from 1939 onward, involved an independent rediscovery of a phenomenon and technique variously called "electrography," "electrophotography," and "corona discharge photography." The underlying physics (which makes xerographic copying possible) was explored as early as 1777 by Georg Christoph Lichtenberg (see Lichtenberg figures). Later workers in the field included Nikola Tesla; various other individuals explored the effect in the later 19th and early 20th centuries. Yet Kirlian took the development of the effect further than any of his predecessors.
In controversial metaphysical contexts, Kirlian photography, Kirlian energy, and so on, are sometimes referred to as just "Kirlian." Kirlian made controversial claims that his method showed proof of supernatural auras, said to resemble a rough outline of the object like a colorful halo. One of the more striking aspects of Kirlian photography is its reputed ability to illuminate the acupuncture points of the human body. An experiment advanced as evidence of energy fields generated by living entities involves taking Kirlian contact photographs of a picked leaf at set periods, its gradual withering being said to correspond with a decline in the strength of the aura. Scientifically, it is considered more likely that as the leaf loses moisture it becomes less electrically conductive, causing a gradual weakening of the electrical field at the drier edges of the leaf.
Kirlian photography is completely different from "Aura photography," in which a colorful image is produced of a persons face and upper torso, using various methods of biofeedback. People commonly use the term "Kirlian photography" to erroneously refer to "Aura photography," and vice-versa. The terms have almost become interchangeable, even though the techniques are completely different. This leads to confusion among those who not familiar with the two different techniques. The Kirlian technique is contact photography, in which the subject is in direct contact with the film which is placed upon a metal plate that is charged with high voltage, high frequency electricity. In Aura Photography, no high voltage is involved as with the Kirlian technique, and no direct contact with the film is made. The images made with an Aura camera do not result from coronal discharge, the colors are projected with fiber optics.
Kirlian's work, from 1939 onward, involved an independent rediscovery of a phenomenon and technique variously called "electrography," "electrophotography," and "corona discharge photography." The underlying physics (which makes xerographic copying possible) was explored as early as 1777 by Georg Christoph Lichtenberg (see Lichtenberg figures). Later workers in the field included Nikola Tesla; various other individuals explored the effect in the later 19th and early 20th centuries. Yet Kirlian took the development of the effect further than any of his predecessors.
In controversial metaphysical contexts, Kirlian photography, Kirlian energy, and so on, are sometimes referred to as just "Kirlian." Kirlian made controversial claims that his method showed proof of supernatural auras, said to resemble a rough outline of the object like a colorful halo. One of the more striking aspects of Kirlian photography is its reputed ability to illuminate the acupuncture points of the human body. An experiment advanced as evidence of energy fields generated by living entities involves taking Kirlian contact photographs of a picked leaf at set periods, its gradual withering being said to correspond with a decline in the strength of the aura. Scientifically, it is considered more likely that as the leaf loses moisture it becomes less electrically conductive, causing a gradual weakening of the electrical field at the drier edges of the leaf.
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