Improvements on the Daguerreotype. 487 pears in shade, and we thus obtain from the Daguerreotype plate either a positive or a negative picture, according to the light in which it is viewed. If we judge of an art by the beauty of its productions, we can scarcely deny that the Daguerreotype, as applied to landscapes and inanimate objects, came almost perfect from the hands of its inventor. The time of exposure in the camera was too long to make it applicable to the delineation of living objects; and though M. Arago remarked, "that a very slight advance beyond his present progress will enable M. Daguerre to apply his processes to the execution of portraits from life," yet the acceleration of the process, and the successful delineation of the human form, were effected by the genius of other artists. The first portrait from life taken by the Daguerreotype was taken on the 6th October 1839, by Mr. Walcott of New York, upon a plate about the size of a sixpence, now in the possession of Mr. Johnson of that city, and portraits were afterwards taken by Messrs. Draper, Mapes, Johnson, and others. The art of taking portraits has been particularly studied, and brought to a high degree of perfection, by M. A. Claudet, who was the first person who discovered, in the beginning of May 1841, an easy and sure method of accelerating the action of light upon the film of iodine, and thus greatly shortening the process. M. Edmund Becquerel had, indeed, shown that one-half of the spectrum, viz., the blue and violet half, had alone the power of exciting the iodine, in forming the picture, and that the other half, though destitute of the power of excitation, had the property of continuing the action of the blue and violet rays after they had produced a slight effect. Hence he shortened the time of sitting for a portrait, by keeping it in the camera for a very short time, and completing the action by making the sun's light pass through a red glass, and shine upon the plate for a few minutes. This process, however, was not suited to the professional artist, and we believe is not now practised. M. Claudet's invention could not fail to supersede it. He discovered that the sensitiveness of the iodized plate was increased in a very remarkable degree by the action of the chloride of iodine or bromine, and when the plate, before it had acquired the appearance of a yellow tint, was held, for about two seconds, over the mouth of a bottle containing either of these chlorides, the vapour spread itself over the iodine film, which soon acquired the proper yellow colour when placed in the iodine box. Various methods of applying these accelerating substances, have been employed. M. Fizeau exposes the iodized plate for a few seconds to a very dilute solution of bromine in water, while others fill a vase with the vapour of bromine and chlorine by means of a syringe, which shall just contain as much vapour as will coat the plate. The accelerating power of the Iodine or Bromine vapour was so great, that M. Claudet obtained with it pictures in ten seconds, which would have required four or five minutes by the original preparation of Daguerre. A new and very ingenious method of giving sensibility to the iodized plate, has been recently proposed by Mr. Bingham. In order to avoid the use of water for dissolving the bromine, he combines bromine with hydrate of lime, and forms a sort of bromide of lime. This may be done by allowing bromine vapour to act upon hydrate of lime for some hours, or more conveniently by placing some of the hydrate at the bottom of a flask, and then putting some of the bromine into a glass capsule, supported a little above the lime, the lower part of the flask being placed in water of the temperature of about 50°. The lime gradually becomes scarlet, like the red iodide of mercury. By slightly colouring the silver plate with the chloro-iodide, and then exposing it for a proper time over the bromide of lime, Mr. Bingham says that pictures may be obtained in a fraction of a second, even late in the afternoon! The accelerating American mixture, prepared by Mr. Walcott, viz., chlorine combined with bromine, and the Hungarian mixture of M. Guerin, which is a compound of bromine, chlorine, and iodine may be obtained in the solid state by a combination with lime, like the bromine colour; but Mr. Bingham greatly prefers the pure bromide of lime as the quickest accelerator yet known.* Soon after M. Claudet's discovery of the accelerating property of the chlorides of iodine and bromine, M. Gaudin of Paris tried the bromide of iodine without chlorine, and this compound is now generally employed by photographers as highly sensitive, and producing the very best results. When this compound of iodine and bromine is correctly prepared, it is of little consequence whether the plate be exposed a shorter or a longer time to its vapour, which is not the case when they are applied separately. With the bromide of iodine the two ingredients evaporate in due proportion, and provided neither of them be in excess on the plate, the coating will highest degree of sensibility. possess its The following accelerating solution, which has been kindly communicated to us by its author, Dr. Karsten of Berlin, not only imparts a high degree of sensitiveness to the iodine film, but gives a fine colour to the picture. Make a saturated solu * See London and Edinburgh Philosophical Magazine, October 1846, vol. xxix., p. 287. Dr. Karsten's Accelerating Liquid. 489 tion of bromine, on equal parts of fuming nitric and muriatic acids, and then add as much iodine as the solution will dissolve. As the iodine enables the liquid to dissolve more bromine, add as much more as it will dissolve. After this addition it will dissolve more iodine, and so on, till the solution is completely saturated with both these bodies. In this concentrated solution the bromine and iodine are so combined, as to be nearly without smell. To one part of this solution, add one-hundred parts, or thereabouts, of distilled water, till the liquid has the colour of rum, when it will be ready for use. Having iodized the plate to a rose colour, expose it to the vapours of the above liquid, till it assumes a violet colour, and it will be ready to be placed in the camera. Notwithstanding the great degree of sensitiveness to light, which the iodized plate receives from these accelerating substances, they have not yet enabled the photographer to carry on his pursuits with artificial light. Dr. Draper indeed obtained an imperfect picture of the moon by the aid of a lens and a heliostate in half-an-hour, upon an iodized plate. In fifteen seconds the flame of a gas-light gave a distinct stain to his plate, when held close to it, and in one minute the impression was strong. A gas-lamp gave a good representation of a figure on a magic lantern's slide, and with Drummond's light, and the Pea light of the oxyhydrogen blow-pipe, he obtained the same result. Mr. Talbot has found that his sensitive paper darkened when held for five or six seconds close to a wax candle, and it was so distinctly acted upon by the light of the moon, that he took impressions of leaves upon it by moonlight. In 1841, Mr. Goddard, obtained images of busts by gas-light, and by the oxyhydrogen light. Mr. Hunt made similar experiments, and M. Claudet took portraits from nature by the oxyhydrogen light in fifteen or twenty seconds, with an object-glass of short focus; and his own portrait thus taken, was publicly exhibited. He obtained also impressions of black lace by the light of the full moon in two minutes, and even by the light of the stars in fifteen minutes. He likewise obtained an image of the moon in his camera in four seconds, in which the shadowed parts of the disc were visible, and in about the same time the image of an alabaster figure by the light of a candle in fifteen minutes, and a similar image by an Argand lamp in five minutes. Mr. Kilburn has more recently obtained welldefined photographic impressions by the light of a common dip candle in ten minutes, by the smallest fish-tail burner of coal gas in three minutes, and by an oil lamp (a solar one,) in the same time. Next in importance to the acceleration of the photographic process is the perfection of the image which is thrown upon the 490 Photography--Photogenic Focus-Reversion of Picture. iodized plate-not of the visible image which is received and seen on the ground glass, but of the invisible image formed by the photogenic rays. M. Claudet has paid much attention to this subject, and has placed it beyond a doubt that the noncoincidence of the luminous and the photogenic focus, was the cause of the many failures which take place. With cameras of single lenses, the photogenic focus is always more distant than the luminous focus; but M. Claudet found, that with some achromatic cameras, in which the coincidence should have been nearly effected, the photogenic focus was nearer the lens than the luminous focus. This unlooked-for result he ascertained to be owing to an overcorrection of the chromatic aberration of the less refrangible rays, and he found this "to be generally the case with object-glasses in which, by the excess of the dispersive power of the concave glass, or the irrationality of that dispersion, the extreme rays of the most refrangible part of the spectrum are, during the second refraction, diverged in a greater proportion than they have been converged by the refraction of the convex lens; and these rays being nearly invisible, do not affect the achromatism of the luminous rays." M. Claudet, therefore, recommends that the rays of the photogenic spectrum should be united in one focus, even at the sacrifice of the achromatism of the more refrangible rays. As the photogenic focus, however, will change its place with the colour and intensity of the light, and with the distance of the object, the photographer should determine experimentally its position in relation to these varying influences. In many of the early Daguerreotypes the pictures were reversed-that is, the right side of the picture was the left side of the landscape; but this intolerable evil, which does not take place in the Talbotype, was soon corrected-in some cases by reflexion from a glass or metallic mirror, and in others by a prism, which is decidedly the best. As much light, however, is lost by these reflexions, and the time of sitting prolonged, artists have scrupled to correct the reversion of the picture. M. Claudet, indeed, is, so far as we know, the only person who makes a point of correcting the reversion of the picture; and he has placed it beyond a doubt that a picture not reverted, is a more artistic and truthful representation of the individual than a reverted one. We have long been convinced of this truth; and if any person doubts it let him look at the two sides of a Calotype made transparent by the process which we have already described, and though the two portraits are mathematically the same, he will see that in the air and even in the likeness, they are essentially different. By means of these processes, portraits of a very superior Gilding-Electrotyping. 491 character are now taken professionally by several distinguished artists in the metropolis, by M. Claudet, Mr. Kilburn and Professor Highschool, each of whom have distinguishing excellences of their own. M. Claudet's long experience in the art of Daguerreotyping has enabled him to produce portraits of great beauty and force. The portraits taken by Mr. Kilburn, and coloured by a celebrated Parisian artist, M. Mansion, are exceedingly attractive, while those of Professor Highschool, from America, executed by new processes, and some of them tinted by peculiar methods, exhibit great chemical knowledge, and evince much experience in the practice of his art. He has employed with much success the vapours of cadmium, antimony, arsenic, and also of several metallic alloys, and from his devotion to the subject we have no doubt that he will make still greater additions to the resources of photography. His very interesting series of panoramic views of the Falls of Niagara, were, we believe, the first ever taken by the Daguerreotype. The Daguerreotype pictures produced by the methods which we have now described, being caused by a slight deposit of mercury, resembling the bloom upon a plum, which is effaced by the slightest touch, could scarcely be regarded as durable or permanent works. In order to remedy this evil, M. Dumas proposed to protect them with some transparent vegetable varnish; but as this coating was not proof against damp and atmospheric influences, it has never been satisfactorily applied. The object, however, which Dumas contemplated has been effected by M. Fizeau, by a very beautiful and simple process. Having covered the silver plate containing the picture with a solution of chloride of gold, mixed with a solution of hyposulphite of soda, in certain proportions, and then exposing the plate to the gentle heat of a spirit-lamp, the metallic gold is precipitated upon the plate, and forms a thin transparent coating, which gives a rich tone to the picture. The gold precipitated on the plate forms an amalgam with the molecules or crystals of mercury, and by adding to their size increases the brilliancy and force of the picture. Other metals have been precipitated by the electrotype process, but the precipitates are less transparent and adhesive. The process of M. Fizeau, besides fixing the picture, enables the artist to colour his portraits-a most desirable result, which could not have been otherwise effected. To the same ingenious author, M. Fizeau, we owe the beautiful art of reproducing the Daguerreotype pictures by the electrotype process, which was discovered in the same year with the Daguerreotpye. In this new process metals are precipitated The process of M. Fizeau was communicated to the Academy of Sciences on the 15th and 24th May, 1841. |