Text from Joel Snyder, On the Art of Fixing a Shadow
The commotion created in late 1837 by the rumors of Daguerre's invention struck the Englishman William Henry Fox Talbot with special force. During 1834 and 1835, Talbot had devised a process based on the light sensitivity of silver salts that allowed him to make photographs with a camera. Tales about Daguerre's process, while exceedingly vague. suggested to Talbot that the Frenchman had invented a procedure using the same principles he had discovered three years before. He quickly arranged to present a paper to the Roval Society to which he belonged, in late January of the coming year in order to establish his priority as the discoverer of certain basic photochemical principles and their application to the production of pictures.
Talbot need not have been so concerned. His discoveries were quite different from Daguerre's and his pictures, which he called "photogenic drawing," were crude and incomplete by comparison with well-made daguerreotypes. Nonetheless, his method contained the seed of modern photography, for unlike Daguerre's, Talbot's was a primitive photographic printing process.
Talbot's interest in photography grew out of his inability to draw. While on his honeymoon in Italy, he tried to sketch the scenery around Lake Como with the aid of a camera lucida - an optical drawing aid. This brought to mind a previous failure at drawing in which he used a camera obscura:
And this led me to reflect on the inimitable beauty of the pictures of nature's paintings which the glass lens of the Camera throws upon the paper in its focus - fairy-pictures, creations of a moment, and destined as rapidly to fade away.Talbot's experiments began early in 1834, and he turned to silver nitrate as had Wedgwood and Niépce before him. His initial tests evolved into a procedure in which paper was coated with a solution of table salt, allowed to dry, and then re-coated with silver nitrate. Talbot discovered that the resulting silver chloride was more sensitive and more predictable than silver nitrate used alone. He used this "salted paper" successfully to make solar photomicrographs, photograms of botanical specimens and items like lace, and contact prints of engravings. He found that the prints could be stabilized successfully by bathing them in a strong solution of table salt or potassium iodide. Talbot's prints were tonally reversed, but in certain cases (with white lace), this worked to his advantage, while in most other cases (the botanical specimens) the reversal was unremarkable. In some cases, though, the problem is severe; a contact print from an engraving will produce a negative picture.
In February 1835, Talbot worked out a solution to this problem; to re-reverse the tonality of a print, the negative picture had only to be printed in contact with a fresh piece of sensitized paper. As it turned out, this procedure was correct in principle, but his photographic materials were most usually incapable of producing negatives with sufficient density to allow the successful printing of positives.
Talbot next devised a method of making specially "sensitive paper" by brushing and rebrushing it with repeated, alternate baths of salt water and silver nitrate, and then turned to experiments with the camera. His first camera negatives, which were quite small, took "an hour or two" to expose in bright sunlight. Talbot notes in his Royal Society lecture:
I obtained [with the camera] very perfect, but extremely small [negative] pictures; such as without great stretch of the imagination might be supposed to be the work of some Lilliputian artist. They require indeed examination with a lens to discover all their minutiae.In late January 1839, Talbot displayed at the Royal Institution a set of his prints made in 1834-1835 and delivered a paper to the Royal Society announcing his invention. Although no exact list of the exhibited prints remains, contemporary accounts indicate that there were photograms of botanical specimens, negatives made from engravings, camera negatives of buildings and sculpture, and some negative photomicrographs. He also showed two or three positive prints from negatives of engravings, but he showed none made from camera negatives, because they were too faint to be used in printing.
Thus, by the autumn of 1839, two photographic processes had been made public; the daguerreotype, which gave astonishingly detailed, highly finished camera-originated pictures, and Talbot's photogenic drawing process, which allowed the production of photograms, camera-originated negatives, and positive prints from negatives of engravings. In terms of its practical possibilities, the future of photography seemed entirely with the daguerreotype.
The crux of Talbot's problem lay with the character of his camera negatives; even after he substituted silver bromide for silver chloride to produce more "vigorous" negatives, they were insufficiently dense to produce anything but dull gray positive prints. Moreover, camera exposures of photogenic drawing paper were prolonged and accordingly placed a strict limitation on what might serve as a possible object of photographic depiction - anything that could remain static for an hour or more.
By mid-1840, Talbot had devised an entirely new procedure for making negatives. He brushed paper with potassium iodide and silver nitrate to produce a bright yellow coating of silver iodide (the active compound in the daguerreotype), which was, however, quite insensitive to light. These sheets, called "iodized paper," could be made many months before they were needed. Just prior to making a camera negative, the iodized paper was brushed with "gallo-nitrate of silver" (a solution of silver nitrate, acetic, and gallic acids) and placed, while still moist, into the camera.
Depending upon the strength of the sunlight, exposures ran from a few seconds to a minute or two. The exposed sheet was brushed with more gallo-nitrate of silver in a darkroom until a vigorous negative was completely developed. Talbot now used this negative as a master from whlch positives were made on his photogenic drawing paper. The new process, named "calotype" (from the Greek words kalos and typos, or "beautiful print"), was patented by Talbot in February 1841.
During printing, the fibrous structure of the paper negative diffuses the light passing through it to the printing paper and obscures the details in the negative. Talbot found he could increase somewhat the resolution of detail in his prints by waxing the negative after processing, making it more translucent. Although prints from his calotype negatives lacked the hard-edged precision of daguerreotypes, their overall effect was substantially closer to the naturalistic, suggestive mode of depiction favored by many illustrators and artists of the time.
The invention of the first photographic processes was virtually complete by 1841. Some details of the calotype process remained to be ironed out and Talbot completed them within two years; at the same time, daguerreotypists discovered that using bromine in conjunction with iodine "quickened" daguerreotype plates and thus permitted exposures to be counted in seconds rather than minutes. But the future of photography remained unclear, the course of its practical use uncharted.
Buying posters through this link
supports Masters of Photography