CHAPTER XXI.
ON THE PHOTOGRAPHIC DELINEATION OF THEPICTURES CREATED BY THE KALEIDOSCOPE.
In a preceding chapter we have referred to the delineation of the pictures created by the Kaleidoscope, when they are received on the ground glass of a camera obscura, or when a camera lucida is placed at the eye-end of the instrument. Both of these methods are very imperfect, and when the pictures have been copied for useful purposes, we believe that they have generally been executed by a skilful draughtsman, who delineated carefully one of the sectors of which the figure is composed, and then repeated it so as to complete the picture.
Fig. 52.
Fig. 52.
Since the invention of the Kaleidoscope, the discovery of the photographic art—of the Daguerreotype and Talbotype processes, has given a new value to the instrument. By means of a Kaleidoscope Camera, the most complex figures can be almost instantaneously transferred to paper, or to plated copper, and hundreds of designs offered to the choice of the artist who is to employ them. The very same figure which is obtained by one mode of illumination, may be altered indefinitely, by merely changing the direction or the intensity of the light, all theobjects which give the figure remaining fixed in the object-box. The optical arrangement by which these figures may be copied, photographically, is substantially the same as that which is shown inFig. 52, whereC G D Fis the Kaleidoscope,A Othe object-box, andL La small achromatic lens, of rock crystal or glass, a quarter of an inch in diameter, placed in contact with the extremities of the glass or metallic reflectors, and having its centre immediately behind the small opening atE. When the rays of the sun, or any other strong light, containing the actinic rays, are thrown obliquely upon the object-boxA O, an image of the Kaleidoscopic figure, produced by the objects in the object-box, will be formed atP P, in the focus of the lensL L. If the focal length of the lensL Lis equal to one-halfC G, the length of the Kaleidoscope, the image will be formed behindL L, at a distance equal toC G, and of the same size as the object-box; but if the focal length ofL Lis greater than the half ofC G, the image will be formed at a greater distance thanC G, behind the lens, and the size of it will be greater than that of the object-box, the distance and the size of the picture increasing as the focal length of the lens increases; and when it becomes equal toC G, the size and the distance of the picture will be infinitely great. When the focal length of the lens is less than halfC G, the figure will be smaller than the object-box, and nearer the lens.
Every camera employed for the purposes of photography may be readily adapted for taking the pictures formed by the Kaleidoscope. We have only to take out the lens or lenses which belong to it, and place the Kaleidoscope furnished with its lensL L,Fig. 52, in the inner tube, which is movable by means of the rack and pinion. If the picture can be made distinct on the grey glass by the rack and pinion, a negative or positive copy of it may be taken on collodion or paper, in the same manner as other photographs. In some cameras the end of the box which contains the grey glass is movable, backwards and forwards, so that the adjustment for rendering the picture distinct may be effected, though the Kaleidoscope is fixed in the front portion of the box.
When the camera is made for the express purpose of taking Kaleidoscope pictures, it becomes a very simple instrument and may be constructed easily and cheaply. It requires no lens excepting the small oneL Lof rock crystal or of glass, a quarter of an inch in diameter. The aperture required for this lens is so small that the spherical and chromatic aberration cannot injure, in any sensible manner, the distinctness of the picture. The difference between the chemical and luminous focus, which cannot be made to coincide with a single lens, may be easily determined by experiment, or in order to avoid this, the small lens may be made achromatic.[16]
The form of the camera as fitted up with one of Mr. Bate’s Kaleidoscopes, with metallic reflectors, is shown in the annexed figure, whereM C D Nis the body of the camera,m n o pthe tube which is moved out and in by a milled head attached to the pinion which drives the rack on the tubem n o p. The KaleidoscopeA B L L, exhibiting the figure which is to be copied, is temporarily fixed in this tube by pieces of cork or wood, so that its axis, or the line of junction of the reflectors, may be perpendicular to the surface of the grey glassp q, which can be taken out, so as to allow the collodion or paper slide to be placed in the same groove.
Fig. 53.
Fig. 53.
The pictures should always be taken, when it is possible, by sunlight incident obliquely upon the object-box, or with the illuminators already described. When this cannot be done, artificial light, containing the actinic or chemical rays, may be thrown upon the object, as shown inFig. 52. The light of coal gas, which may be condensed for any length of time upon the objects in the object-box, will be found to answer the purpose; but if a more rapid process is required, we may, asproposed by Mr. Moule, use the Bengal lights, which contain a large quantity of the actinic rays.[17]These lights are composed ofsixparts ofnitre,twoofsulphur, andoneofthe sulphuret of antimony. The powder is made up in the shape of a cone, which is ignited at the top; but it would be better to spread it out widely, in order that it may be condensed upon the object-box. The lime-ball light may also be employed, but the Bude light, which is a coal gas flame, rendered more intensely luminous by a stream of oxygen, is preferable to any other artificial flame. In using it, or any other of the lights already mentioned, for obtaining Kaleidoscope figures, it must either be placed very near the object-box, or condensed upon it by a large lens, on account of the small size of the aperture at the eye-end of the Kaleidoscope.
In the formation of the Kaleidoscope figures, it is necessary to pay particular attention to the colour of the objects of which they are to be composed,red,orange, anddark yellowobjects, which transmit few, if any, actinic rays, should not be employed. Blue glasses, which transmit no red rays, are actinically more luminous than colourless glasses, and therefore pale blue, pale green, and pale yellow glasses may be advantageously combined with colourless glasses as objects for the object-box.
When we wish to copy photographically the pictures obtained from external objects, we must use the Telescopic Kaleidoscope of Mr. Bates, by which the images of these objects are formed at the extremity of the reflectors. These objects may be flowers, plants, architectural ornaments, or parts of them, paintings, photographs, statues, or loose and irregularly placed materials of any kind. In the figures created bythe common Kaleidoscope, we must trust to chance for the formation of the figures, and can only choose those which we like out of a large number accidentally formed; but when we make use of external objects, we can group them and illuminate them in any manner we choose, selecting those forms and colours which, when combined, produce the effect that we desire.
This power, of arranging the objects, when in contact with the ends of the reflectors, may be obtained with the Kaleidoscope of Mr. Bates, shown inFig. 29, by removing the anterior half of the cone when the objects are opaque, and placing the camera in a vertical position. The objects being placed upon a horizontal plate, may, if opaque, be illuminated, by reflected light, and the picture of them, when combined by the Kaleidoscope, taken in the same manner as when the instrument was in the position shown inFig. 52. If the figure is not what we like, we can shift any individual object, or remove it, or replace it by another, till we are satisfied with the combination.
The very same power of altering the combination, may be obtained for transparent objects. We have only to place these objects on a horizontal plate of glass, not connected with the Kaleidoscope, but capable of being removed from it, and again brought close to the ends of the reflectors. When the objects on the glass plate have been put into their proper place, so as to give the desired picture, the plate is brought as near as possible to the ends of the reflectors, and the objects are illuminated either by solar or other light reflected upwards upon the object-box.