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HOTOGRAPHY. The fact that light visibly affected matter-darkening some that was light and lightening some that was dark, and changing and discharging colors, must have been noticed before history began to be recorded, although it was not till perhaps the fourth quarter of the 18th century that it began to receive anything like systematic attention; not until Scheele, a Swedish chemist, noticing that silver chloride darkened under the rays of the sun, sought for experimental evidence of the cause and consequence. He found that the action was practically confined to the lower end of the spectrum, the blue-violet and the ultra-violet; and that the result was a liberation of chlorine. Scheele was followed by many others, some of whom added more or less to the desired information; but not till 1791 does any one seem to have thought of it as a means of picture-making; at which date there is ample evidence in a book, 'Tom Wedgewood, the First Photographer, published in 1803 by Duckworth and Company of London that Wedgewood made photographic copies of pictures, probably using the salts of silver and by "contact printing." A more or less full account of his methods, written by Davy, appears in the Journal of the Royal Institute for 1802, but although it is known that he worked with Davy in the laboratory of the institution it does not appear that the latter had any share in the photographic experiments.

To Nicephore Niepce, however, belongs the honor of getting the first camera image, which he did in 1827, although he had been experimenting since 1814; but as, according to Daguerre, it required an exposure of from seven to eight hours, it left much to be desired; and it is safe to say that practical photography was not reached till 1839. Early in January of that year, Daguerre first reported the results of his process and published a description of the same on 19 Aug. 1839. On 31 Jan. 1839, Talbot, who had obtained permanent prints and camera images as early as 1835, reported his process to the Royal Society, and on 21 February following, published the details of the same. In the early part of 1839, Mungo Ponton, in a paper read at a meeting of the Royal Scottish Society of Arts, made known to the world his discovery that soluble organic matter, in the presence of an alkaline bichromate, was rendered insoluble by exposure to light-a discovery the value of which was not recognized for some years, but which is the basis of all that is included in

"process work," or half-tone engraving. See PHOTOENGRAVING.

Daguerre and Talbot had been working independently and without knowledge of each other for several years, the latter alone and on scientific methods, having been a student of science, especially chemistry, from his school days; the former empirically and, for some time before he reached the goal, in conjunction with Niepce. The latter had been working at the problem since 1814. He obtained camera images in 1827, and two years later, at the solicitation of Daguerre, entered into partnership with him. From the documentary evidence available, it is at least certain that the suggestion of the action of iodine on a silver platewhich led to ultimate success - came from Niepce. Be that as it may, it is worthy of notice that, working on different lines and with different material, Daguerre and Talbot found success in the same metallic haloid, the same silver iodide, although made in a very different Iway and giving very different results. Each was able to secure photographic impressions, one on sensitized paper, the other on a sensitized plate, but were unable to prevent the image from fading out until Sir John Herschel, in 1839, discovered that hypo-sulphite of soda dissolved out the silver unaffected by light, thereby fixing the image. Daguerre's process, to which he had given the name "daguerreotype," consisted in exposing the highly polished surface of a silver plate, or a copper plate coated with silver, to the vapor of iodine. The silver iodine thus formed passed through various colors, depending on the length of the exposure, and experience soon showed the color which had the highest degree of sensitiveness. This, on exposure in the camera, produced no visible image, but, on exposing the plate to the vapor of mercury (such small quantity as arose from a temperature of about 140°), an image was developed, the mercury vapor having adhered to such parts as had been acted on by light, and in proportion to the quantity or intensity of that light.

The image thus formed was of exquisite delicacy, the minuteness of its detail being limited only by the degree of perfection of the optical appliances; but the process was slow, requiring an exposure of minutes. Prof. John William Draper of the University of the City of New York, with improved lenses early in 1840 made the earliest sunlight picture of a human face by this process. The subject was

his sister, Miss Dorothy Catherine Draper. The picture is the property of Sir William Herschell of England. Nearly a year later, Goddard in England and another of the same name in America added bromine, which reduced the exposure to seconds. About the same time an improvement hardly less important was made by Fizeau, known as "gilding," the deposition of an extremely thin film of gold on the surface of the plate, which materially added to the beauty and permanence of the image. The difficult point about the daguerreotype was that it could not be duplicated nor multiplied except by making duplicate original pictures with a plurality of lenses, as is now done with the ferrotype or tin type. Each exposure yielded a picture complete in itself, but only one, a positive; whereas the altogether easier although apparently more complicated method of Talbot gave a negative that could be duplicated from or multiplied to any extent.

Talbot's process (calotype, he termed it, but better known by his own name) had for its support paper, and according to his first description was made as follows: A sheet of paper was brushed over with a solution of silver nitrate, dried and dipped into a solution of potassium iodide and again dried. This he called iodized paper; it was hardly if at all sensitive to light, and would keep indefinitely. To make it sensitive, it was brushed over with what he called gallo-nitrate of silver, a mixture of solutions of silver nitrate and gallic acid; and after exposure on the camera the image was developed by brushing over with the same solution and the application of a gentle heat. The image so produced was a "negative"; that is, the lights and shades were reversed, darks in the subject being represented by lights or white paper and vice versa. The advantage of this lay in the fact that a sheet of the same paper placed under this negative and exposed to light resulted in a positive, an image in which the lights and darks were in their right position; and that an unlimited number of such positives could be made from such negative. But as positives on calotype paper would require development, the same as the negative, Talbot recommended the employment of the silver chloride paper first brought before the Royal Society, which simply required exposure to light, or what is now known as "printing-out paper." To facilitate this printing, and to avoid as far as possible the grain of the paper in the paper negative, he subsequently saturated it with wax; and later on, paper iodized and waxed, or "waxed paper," became an article of

commerce.

About 1840 "amateur" photographers came on the stage. Le Gray's wax-paper process, a modification of the talbotvpe, which consisted in waxing the paper before iodizing it, came into use; it was slow yet yielded fine results, so fine, indeed, that some of the negatives made then are quite equal to anything turned out at the present time, notwithstanding all the improvements. The albumen process, first proposed by Niepce de Saint Victor, a nephew of the original Niepce, was perfected by Le Gray about 1850. Iodized albumen was spread on a glass plate and sensitized by immersion in a solution of silver nitrate; and it gave results that for delicacy of detail have not been equaled

except by the daguerreotype; results so perfect that for certain purposes such as transparencies for the stereoscope and for enlarging it has no equal, and consequently is still in use.

In 1850 the introduction of a practical method of employing collodion as the sensitive film and glass as its support gave photography a new impetus. Collodion, a solution of a variety of gun-cotton, in a mixture of alcohol and ether, was suggested by Le Gray, in 1850; but it remained for Scott Archer of London in 1851 to give it a practical form. Compared with the daguerreotype, it was simplicity itself, while in delicacy of detail and beauty it was not far behind; and more important still, the image might be either positive, so as to be available at once, or negative, with all the advantages of unlimited multiplication. The image on a collodion plate is positive when examined by reflected, and negative by transmitted, light. With a comparatively short exposure and development, the plate needs only backing with some black substance to supply the shadows to convert it into a very beautiful picture. With longer exposure, and development continued until the highest lights are opaque, followed by intensification, it need be, the image is negative, and capable of giving prints of the very highest quality. The developer used is a solution of sulphate of iron and acetic acid, while the fixing agent to fix or dissolve out the film unacted upon by light, is a solution of cyanide of potassium. From this duality of the collodion film there arose two classes of professional photographers, the few, with higher ideals and catering to the better class of the people, adhered to negatives of considerable size, generally "whole plate," 81⁄2 x 61⁄2 -supplying only one print at a time. The other class, the many, contented themselves with small positive prints, and the "carte de visite" soon displaced the glass positive, or, as it was called in America, "ambrotype."

But collodion, or wet collodion, as in the light of after developments it was called, however convenient for the professional, heavily taxed the amateur who went afield. The plates had to be prepared and finished on the spot which entailed, even when only the smaller sizes were used, the transportation of an amount of apparatus and material that would greatly incommode a modern amateur. This led to a demand for a process that could be employed in the field as easily as wax paper, and, after many attempts, the result was what was then known as "dry collodion," 1856-57. A dry collodion plate differed from a wet in having the free silver nitrate washed away; but if then dried and exposed, only a weak, useless image could be obtained, as it required something to take the place of the silver as an absorber of the liberated iodine and bromine. This absorber, or sensitizer, as it was called, consisted first of certain preparations of gelatine, then tannin, and ultimately almost any kind of soluble organic matter, tea, coffee, malt, beer, albumen, etc. Such plates were slow, 5, 10 and 15 minutes being quite usual, even on well-lighted landscapes, and although it was a great relief to have nothing to take to the field but a dozen plates in half as many double slides or plate-holders, the amateur was not satisfied. The next step in advance was the introduc

tion by Sayce and Bolton of the "collodiobromide emulsion in 1864–65." This did away with the troublesome preparation of the plate in the silver bath, it being only necessary to pour the sensitized emulsion directly on the plate and set it up to dry. Exposures were now much shorter, but still far behind wet collodion, and so the search for greater rapidity continued. Henry J. Newton, in 1870, prepared a collodiobromide emulsion of considerable sensitiveness, which was successfully used prior to the introduction of the faster process. The emulsion idea was really the turning-point. In 1871 Dr. R. L. Maddox of England, while using photography as an aid in his microscopical work, discovered the possibilities of an emulsion composed of isinglass, gelatine and bromide of silver, and published a description of his process that year in the British Journal of Photography, submitting specimen negatives to the publishers. His process may be said to be the beginning of the now universally used gelatino-bromide process, commonly known as the "dry plate" process. In the preparation of the emulsion, only certain kinds of gelatine are suitable, and much time was spent in discovering which was the best. King, in 1873, improved the emulsion by washing out the free silver, thereby increasing its rapidity. In the same year Burgess began the manufacture and introduction of prepared plates. Bennett in 1874 sold dry sensitized emulsion or pellicle which could be prepared for coating plates by simply dissolving in hot water. In 1878 Bennett made a great step in advance by "cooking" or heating the emulsion at a given temperature. This wonderfully increased the sensitiveness of the emulsion to light to such an extent that glass plates coated with a film of it became from 30 to 50 times more sensitive to light than wet collodion, which was then considered standard. At a meeting of one of the London societies, Bennett showed full-timed negatives made with such brief exposures as to fairly astonish those present. Mockhoven in 1879 discovered that by the introduction of ammonia into the emulsion remarkable rapidity was obtained nearly equal to the "boiling or heating" method of Bennett. Very soon several dry plate manufacturers began to supply the prepared plates for the use of photographers. About 1880-81 plates began to be made in the United States by Cramer and Norden, photographers in Saint Louis, Mo., and John Carbutt in Philadelphia. It was a new industry, for theretofore photographers were required to prepare their own plates.

In 1884 A. L. Henderson, an English photographer, demonstrated before the Society of Amateur Photographers of New York, the process of making a gelatino-bromide emulsion. The general process is shown in the following formula as used by Henry London:

First make the following two solutions:

Heinrichs' special gelatine.. Nelson's No. 1 gelatine. Distilled water..

No. 3.

3

34 grams

4 grams 180 c. c.

No. 1 solution is thoroughly mixed by being placed in a hot water bath and agitating, then in a darkened room illuminated only by a faint non-actinic light. No. 2 solution is mixed with No. 1 solution in the form of a fine stream so that the silver may come in contact with the bromide and be converted into bromide of silver. After cooling to 90° F. a solution of alcohol 5 cubic centemeters (nearly 2 drams) and ammonia (Sp. Gr. 910) - 110 minims is added a little at a time. The emulsion is then kept under heat over night at a temperature of 100° F. and solution No. 3 heated up to 125° F. and then cooled down to 100° F. is added to the sensitized solution. The whole is allowed to cool until it solidifies into the form of a jelly, this is compressed and sifted through a screen until it is broken up into small particles and is then washed for several hours. The water is drained off and the emulsion dried. It is then melted at a temperature of 135° F. and 20 cubic centemeters of alcohol is added. Is filtered while liquid in a warm condition, and then coated upon leveled glass plates usually placed upon a marble slab. On cooling the film solidifies, the plate is then removed and for use in the camera.

placed in a drying closet. After this operation it is ready

The foregoing is the basis of the process now used by all the large manufacturers of dry plates, who consume many tons of silver gelatine and glass to supply the demand. Specially constructed machinery is used for preparing and coating plates and paper with the sensitive emulsion on a large scale. To explain the magnitude of this work, there was made in 1903 a single positive print on gelatino-bromide paper in Germany 40 feet long by 5 feet wide. A special building was constructed to hold the immense reel, over 13 feet in diameter, on which the exposed paper was wound and developed.

The convenience to the novice or skilful photographer of having a sensitized plate ready prepared and capable of being used at any time, gave a great impetus to photography, and extended its field of usefulness in a remarkable degree. The great sensitiveness of the plates facilitated the practice of instantaneous photography which led to the manufacture of the hand camera, an instrument carried in the hand by a handle, having a finder for locating the image to be photographed, a shutter adjustable for rapid or slow exposures, and a focusing device so arranged that the instrument can be used at a moment's notice without the aid of a tripod. The first practical machine of this kind was ininvented by a German, M. Schmid, and was introduced by E. and H. T. Anthony and Co. of New York in 1884-85. It was found that the sensitized solution could be applied to celluloid transparent film as well as to plates. This lightened the work of the photographer and avoided the danger of breakage which the use of glass entailed. John Carbutt of Philadelphia was the first to introduce coated cut celluloid films in 1883. In 1888 there was introduced by George Eastman of Rochester, N. Y., a new miniature hand camera named the "kodak," which carried spools or rolls of paper sensitized with a film of gelatino-bromide emulsion of sufficient length to take at least 100 small pictures about three inches in diameter. After