تويت
التصوير الفوتوغرافي الحديث
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تجارب أخرى .. داجوير
FURTHER EXPERIMENTS
In the meantime , Thomas Wedgwood and Sir Humphrey Davy were experi menting along the same lines as Professor Charles . They coated paper and white leather with a solution of silver nitrate and , after placing an opaque object on the top of this prepared paper , exposed it to sunlight . The unprotected portion darkened , while the protected part remained white .
These two experimenters then tried using this coated paper under paintings on glass . The rays of light passing through the transparent and semi - transparent portions of the painting , darkened the paper and gave them a negative picture . They also found that the blue rays of light were much more effective than red and yellow rays .
These two men made some progress but they , too , like Professor Charles , were stopped by the fact that they could not make their pictures permanent .
Thomas Wedgwood and Sir Humphrey Davy experimented with the camera obscura by allowing the image to fall on a sheet of sensitized paper , but the coating was too insensitive for the light to make much of an impression on it .
About 1814 , Joseph Nicephore Niepce , a French chemist , began his photographic experiments . During the years from 1823 to 1825 he worked to produce asphaltum photographs on glass and metal . He coated large sheets with a thin layer of bitumen ( natural asphalt ) dissolved in oil of lavender . He exposed this to light under a drawing on paper that had been varnished to make it more transparent . After an exposure of about an hour to strong sunlight , the bitumen on the metal that had been protected from the light by the opaque parts of the drawing was washed away with oil of lavender , leaving a negative image of the drawing . After washing off the soluble bitumen that was not affected by the exposure to light , he applied an acid to eat away the metal . This process is still used in a modified form for making some types of printing plates .
DAGUERRE
Perhaps the best known of these early experimenters is Louis Jacques Mande Daguerre , the inventor of the Daguerreotype process . Daguerre was born near Paris in 1787 and about 1824 he began experimenting to find a way of fixing the image produced in the camera . He was a scenic painter and used the camera as a help in reproducing natural scenes .
Daguerre was quite unsuccessful in these experiments , but he did not give up . He neglected his scenic painting business and devoted himself to these unsuccessful experiments so assiduously that his wife became alarmed as to his sanity . In 1829 Daguerre and Niepce entered into partnership under which each agreed to share with the other any discoveries either might make .
In 1837 , Daguerre quite accidentally discovered what is now known as the Daguerreotype process . He was using metal plates coated with a combination of silver and iodine and after two or three hours exposure in the camera he would get a faint image on the metal plate . One day , as Daguerre was making an exposure , the sun went behind some clouds so that there was not enough light to give him a good picture . He , therefore , discontinued the exposure and put away the lightly exposed plate in his chemical cabinet , intending to use it again when the sun was shining . The next morning , to his pleasure and surprise , upon picking up this plate , he found it to have a distinct and perfect picture . He coated another
plate , underexposed it , and placed it in the " magic - cabinet " overnight . The next morning he found another beautiful picture .
Daguerre did not know what caused this strange development of the picture . Using the process of elimination , he exposed plate after plate and with each exposure certain chemicals were removed from the cabinet . Finally he found that the vapor from a bowl of mercury was the developing agent .
Daguerre kept the process he had discovered a secret until June 1839 when he published the details at the request of the French government . He was awarded an annual life pension of six thousand francs .
These Daguerreotypes were beautiful and have never been surpassed for delicacy of tone . Actually they are very thin negatives backed with silver or other metal . Being negatives , they are reversed as to right and left .
In Daguerre's time the plates used , coated with iodine , required an exposure of from five to thirty minutes . The process was modified later so that the exposure was reduced to about thirty seconds . In those days having a portrait taken was quite an ordeal .
A few months before the publication of Daguerre's process , Henry Fox Talbot , who had been experimenting with coated paper and leather , showed the results of these experiments at the Royal Society . These he called " photogenic drawings . " Talbot produced an image on paper , whereas Daguerre's was an image on a polished silver surface .
The calotype or talbotype process was patented by Talbot in 1841. This was the third British patent for photography , the two previous ones having been granted to Daguerre . This patent was granted for a process for obtaining a negative on paper . It was very popular for several years but was later superseded by the collodion process .
In 1843 , Talbot patented the use of sodium thiosulfate ( hypo ) for making pictures permanent . This process had been suggested in 1819 by Sir John Herschel . In 1854 , Talbot coated paper with albumen to produce a glossy surface .
Other experimenters , Le Gray , Hunt and Pollock , worked on this idea in 1851 , 1852 and 1853 , and for many years albumen paper was one of the most popular of printing processes . It was supreme until the introduction of gelatino - chloride paper commonly called P.O.P. - printing - out paper , as distinguished from developing paper .
التعرف على تاريخ التصوير ..
تجارب أخرى .. داجوير
FURTHER EXPERIMENTS
In the meantime , Thomas Wedgwood and Sir Humphrey Davy were experi menting along the same lines as Professor Charles . They coated paper and white leather with a solution of silver nitrate and , after placing an opaque object on the top of this prepared paper , exposed it to sunlight . The unprotected portion darkened , while the protected part remained white .
These two experimenters then tried using this coated paper under paintings on glass . The rays of light passing through the transparent and semi - transparent portions of the painting , darkened the paper and gave them a negative picture . They also found that the blue rays of light were much more effective than red and yellow rays .
These two men made some progress but they , too , like Professor Charles , were stopped by the fact that they could not make their pictures permanent .
Thomas Wedgwood and Sir Humphrey Davy experimented with the camera obscura by allowing the image to fall on a sheet of sensitized paper , but the coating was too insensitive for the light to make much of an impression on it .
About 1814 , Joseph Nicephore Niepce , a French chemist , began his photographic experiments . During the years from 1823 to 1825 he worked to produce asphaltum photographs on glass and metal . He coated large sheets with a thin layer of bitumen ( natural asphalt ) dissolved in oil of lavender . He exposed this to light under a drawing on paper that had been varnished to make it more transparent . After an exposure of about an hour to strong sunlight , the bitumen on the metal that had been protected from the light by the opaque parts of the drawing was washed away with oil of lavender , leaving a negative image of the drawing . After washing off the soluble bitumen that was not affected by the exposure to light , he applied an acid to eat away the metal . This process is still used in a modified form for making some types of printing plates .
DAGUERRE
Perhaps the best known of these early experimenters is Louis Jacques Mande Daguerre , the inventor of the Daguerreotype process . Daguerre was born near Paris in 1787 and about 1824 he began experimenting to find a way of fixing the image produced in the camera . He was a scenic painter and used the camera as a help in reproducing natural scenes .
Daguerre was quite unsuccessful in these experiments , but he did not give up . He neglected his scenic painting business and devoted himself to these unsuccessful experiments so assiduously that his wife became alarmed as to his sanity . In 1829 Daguerre and Niepce entered into partnership under which each agreed to share with the other any discoveries either might make .
In 1837 , Daguerre quite accidentally discovered what is now known as the Daguerreotype process . He was using metal plates coated with a combination of silver and iodine and after two or three hours exposure in the camera he would get a faint image on the metal plate . One day , as Daguerre was making an exposure , the sun went behind some clouds so that there was not enough light to give him a good picture . He , therefore , discontinued the exposure and put away the lightly exposed plate in his chemical cabinet , intending to use it again when the sun was shining . The next morning , to his pleasure and surprise , upon picking up this plate , he found it to have a distinct and perfect picture . He coated another
plate , underexposed it , and placed it in the " magic - cabinet " overnight . The next morning he found another beautiful picture .
Daguerre did not know what caused this strange development of the picture . Using the process of elimination , he exposed plate after plate and with each exposure certain chemicals were removed from the cabinet . Finally he found that the vapor from a bowl of mercury was the developing agent .
Daguerre kept the process he had discovered a secret until June 1839 when he published the details at the request of the French government . He was awarded an annual life pension of six thousand francs .
These Daguerreotypes were beautiful and have never been surpassed for delicacy of tone . Actually they are very thin negatives backed with silver or other metal . Being negatives , they are reversed as to right and left .
In Daguerre's time the plates used , coated with iodine , required an exposure of from five to thirty minutes . The process was modified later so that the exposure was reduced to about thirty seconds . In those days having a portrait taken was quite an ordeal .
A few months before the publication of Daguerre's process , Henry Fox Talbot , who had been experimenting with coated paper and leather , showed the results of these experiments at the Royal Society . These he called " photogenic drawings . " Talbot produced an image on paper , whereas Daguerre's was an image on a polished silver surface .
The calotype or talbotype process was patented by Talbot in 1841. This was the third British patent for photography , the two previous ones having been granted to Daguerre . This patent was granted for a process for obtaining a negative on paper . It was very popular for several years but was later superseded by the collodion process .
In 1843 , Talbot patented the use of sodium thiosulfate ( hypo ) for making pictures permanent . This process had been suggested in 1819 by Sir John Herschel . In 1854 , Talbot coated paper with albumen to produce a glossy surface .
Other experimenters , Le Gray , Hunt and Pollock , worked on this idea in 1851 , 1852 and 1853 , and for many years albumen paper was one of the most popular of printing processes . It was supreme until the introduction of gelatino - chloride paper commonly called P.O.P. - printing - out paper , as distinguished from developing paper .
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