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ILLUSTRATION No 2.
The length of the box was determined by the angle of reflection from the brightest part of the lamp, to the strips of mirror glass
in the corners of the box, and out to the opposite corners at the front, insuring perfect illumination along the diagonals of the negative.
ILLUSTRATION No. 3.
boxed in, and with a button on the outside of the light box is completely under control.
Illustration No. I shows the arrangement of the light box. The inside dimensions are: 24 x 12 x 12 inches. The distance from the nearest point of the bulb to the front is 18 inches, and the bulb used is one of the new Tungsten lamps for which 250 candle power is claimed, requiring a comparatively small amount of current. The reflecting surface is corrugated mirror glass, arranged in such a way as to eliminate all right angles and make every ray of light active and useful.
With this arrangement there is probably some loss of illumination in medium-sized work, but this is amply compensated for by the perfect diffusion obtained in the greater enlargements described in this article. The focal point of the condensers is about 5 inches in front of the optical center of the lens.
The exposure necessary for a 16 x 20 Royal Bromide print from a 61⁄2 x 81⁄2 negative of average density, proved to be from one to five minutes, while the 6 foot enlargements required from three and a half minutes to half an hour, according to the density of the negative and the quality of the print wanted.
Sliding in grooves under the box just described, and at right angles to the front of the condenser box, is a shelf for supporting the camera. See illustration No. 2.
The boards into which these grooves are cut furnish a firm support for the heavy condensers and reduce the strain on the light box to a minimum. These boards are a trifle thicker than the sliding shelf, allowing the latter free movement in the grooves. The closets and drawers shown in the illustration are used for storing plates and bromide paper.
Telescoping over the light box is the box holding the condensers which are twelve inches in diameter. (Illustration No. 3.) The condensers are adjustable inside this box by means of blocks and screws moving easily in the slots cut in either side of the box. The location of the slots was determined by the weight, height, and thickness of the frames holding the condensers, and is the point at which the condenser frames can be moved with the greatest ease. The set of frames or kits will hold any size negative up to 8 x 10, either vertically or horizontally, and fits into the front of the condenser box.
The condensers are mounted in the manner shown in illustration No. 4, allowing sufficient play to permit of expansion and contraction. Two ground
glasses can be inserted between the condensers, if for any reason the illumination of the negative should appear to be uneven, the eccentric discs in the corners serving to hold them in place. The two frames or cells are locked together by means of screw heads and sockets. The blocks and screws are fastened through the slots on the sides of the box.
The entire apparatus has been in use for two years, and its alignment is as perfect to-day as it was when first installed. The lens used in the camera is of 77% inch focus, which, at a distance from negative to easel of 9 feet, will enlarge a figure measuring 334 inches up to 32 feet. The lens and condensers readily cover a negative measuring 61⁄2 x 81⁄2 inches. Our easel is four feet wide and six feet high, and made of 7-inch stuff heavily and firmly braced.
This enlarging outfit was installed under the joint direction of Mr. W. H. Schoff and the writer, in the photographic laboratory of The Philadelphia Museums, with which institution both are connected. The museum uses bromide enlargements extensively (mostly Royal Bromide paper, toned with sodium sulphide) to illustrate its exhibits, one of the most interesting of which shows the history of commerce. Methods of transportation by water are shown principally by models of boats, beginning with the galleys of the
ancients and leading through the various stages of historical development up to and including the famous "Lusitania," all made to scale. Land transportation is shown by a series of bromide enlargements, and this was made possible by the curious fact that the most primitive and practically all the many successively developed methods are still in use at the present day, in some part of the world. Two hundred 16 x 20 pictures are included in this exhibit.
The illustrative and decorative possibilities of bromide enlargements are perhaps best shown by the following illustrations:
The picture of the "Mongolian Pilgrim," was made with an ordinary No. I Kodak with no accessories other than those furnished by the makers. From the original negative the writer first made a 5 x 7 negative of the leading camel and enlarged that to fit a panel measuring 2 feet by 6 feet. The result is shown in illustration No. 6. In the original, the distance from the top of the man's head to the foremost hoof of the camel is 14 inches, which, in the panel, is increased to 3 feet 6 inches. The actual enlargement is 33.6 diameters or 1128 times the area. The degree of enlargement is shown in the illustration, in the lower left hand corner of which can be seen a contact print from the original negative. A word of praise is certainly due Mr. Willis for his splendid exposure, and to the Eastman Company for the per