The Optical Magic Lantern Journal (June 1890)

The Optical Magic Lantern Journal and Photographis Enlarger. 3 exceeds in dimensions the negative to be taken, add one to the number of times and multiply by the focus of the lens, to show the distance at which the negative must be from the lens. The distance between the lens and the sensitive plate is found by dividing the product above given by the number of times one is larger than the other, the quotient giving the distance. As the lenses emploved for such purposes may vary from 4in. to (6in, in focus, we shall give a few examples. With a lens of gin. focus, and a reduction of two times, the figures representing the distance between the engraving and the lens on the one hand, and the sensitive plate and lens on the other, will be respectively 6in. and 12in. If the reduction is three times, the distances will be Sdin. and 16in. Fora sin. lens for a reduction of two times, it would be 6in. and 20in. Fora 6in. focus lens, the two and three times would be respectively gin. and 18in., and 8in. and 2qin. a Hand Cameras for Obtaining Slides for the Lantern, No. 2.—THE QUADRANT. A NEW camera bearing the name “ Quadrant” is about to be introduced to the public by Messrs. W. H. Humphries and Co., of 268, Upper-street, Islington, N. It is the invention of Messrs. Parfitt and Hume, gentlemen well known in photographic circles. By its Ingenious yet simple construction it will doubtless be much sought after as a means for obtaining negatives, from which may be produced, by contact, lantern transparencies—a branch of photography which has received great impetus of late. The “ Quadrant” hand camera has no projecting knobs in sight, all the movements being effected from underneath the instrument. These movements consist of focussing, changing the plates, setting and releasing the shutter. denotes the plate about to be exposed. The plates—which are contained in metal holders provided with two pivots on the upper part,in such a manner that they will act as hangers—are placed horizontally in a receptacle situated above the camera A disc, also placed under the camera, ; proper (Fig. 1). The pivots of the underneath plate fall between two metallic teeth, fastened on the upper part of a moveable three-sided box or sliding division. The other edge of the plate is supported on a strip of metal, but as soon as the partition containing the serrated metal edge is drawn backwards, the lowest plate is. pulled back sufficient to liberate it from the projecting slip which held it in a horizontal position, when it immediately swings on the pivots into a perpendicular position, where it is ready for exposure. The pivots of the next plate then fall between the second set of teeth, and the plate rests on the metal strip ready to be dropped into the horizontal as soon as the partition above mentioned has again been drawn slightly backwards. Each plate in turn thus falls between its respective set of teeth and drops, and in so doing passes over a slight spring, which retains it in the necessary position for exposure. When it is desired to remove the plates for development, the box with the serrated edge is drawn out through a door in the end of the camera. From the cut (Fig.2), which represents the bottom of the camera, will be seen the various means by which Fic. 2. the motions are imparted. The partition carrying the lens is secured to A, focussing being attained by moving B on the graduated scale C. Under D is a plunger which is pushed into a series of holes or notches in the under side of the sliding box, by a slight movement of G; and bya still further movement strikes on F.and carries the box backwards the required distance. When the lever G is afterwards pushed back to E, the plunger drops so as to allow of its being carried immediately under the next hole. Bar| This movement also causes a ratchet to operate upon a wheel containing numbers, which may be fseen ' through the opening at H. The shutter is a double leaved one, which gives slightly less exposure to the sky than the foreground. It is set by the movement of the lever K, and is released by a touch at the knob L. Newman's pneumatic regulator can be attached for time exposures. It is the intention to supply this camera to hold either 12, 18. or 24 plates, and to fit them with single achromatic and rectilinear lenses, and also with two finders. A camera to hold 12 plates measures roin. by 7in. by sin., and weighs about 6lb. when charged.