A Manual Of Photography

106 HISTORY OF PHOTOGRAPHY. fully in the picture ; for this, it is well that the chair should be brought from the back-ground, from three to six feet. “Those who undertake daguerreotype portraitures will of course arrange the back-grounds of their pictures according to their own tastes. "When one that is quite uniform is required, a blanket, or a cloth of a drab colour, properly suspended, will be found to answer very well. Attention must be paid to the tint: white, reflecting too much light, would solarize upon the proof before the face had time to come out, and, owing to its reflecting all the rays, a blur or irradiation would appear on all edges, due to chromatic aberration. “It will readily be understood, that if it be desired to intro- duce a vase, an urn, or other ornament, it must not be arranged against the back-ground, but brought forward until it appears perfectly distinct upon the obscured glass of the camera. “Different parts of the dress, for the same reason, require intervals, differing considerably, to be fairly copied; the white parts of a costume passing on to solarization before the yellow or black tints have made any decisive representation. We have, therefore, to make use of temporary expedients. A person dressed in a black coat and open waistcoat of the same colour, must put on a temporary front of a drab or flesh colour, or, by the time that his face and the fine shadows of his woollen clothing are evolved, his shirt will be solarized, and be blue, or even black, with a white halo around it. Where, however, the white parts of the dress do not expose much surface, or expose it obliquely, these precautions are not essential; the white collar will scarcely solarize until the face is passing into the same condition. " Precautions of the same kind are necessary in ladies’ dresses, which should not be of tints contrasting strongly. "It will now be readily understood, that the whole art of taking daguerreotype miniatures consists in directing an almost horizontal beam of light, through a blue-coloured medium, upon the face of the sitter, who is retained in an unconstrained posture by an appropriate but simple mechanism, at such a distance from the back-ground, or so arranged with respect to the camera, that his shadow shall not be copied as a part of his body.” Professor Draper used a camera having for its objective two double convex lenses, the united focus of which, for parallel rays, was only eight inches; they were four inches in diameter in the clear, and were mounted in a barrel, in front of which the aperture was narrowed down to three and a half inches, after the manner of Daguerre’s. He also adopted the principle of bringing the plate forward out of the best visible focus, into the focus