The Optical Magic Lantern Journal (December 1892)

The Optical Magic Lantern Journal and Photographic Enlarger. 153 Centreing the Light. Son, of St. John’s Street Road, E.C. The jet was supported midway on a hinged joint upon ! which it could see-saw. The outer end of the Unxess the illuminant be exactly in the axis of | jet beyond the inlet tubes for gas terminated in the optical system of the lantern, and the correct ; the form shown at A fig. 1. A strong spring D, distance fromithe condenser, the disc on the screen : kept A tightly pressed against the points of the will not be evenly illuminated. screws B and C. It will thus be evident, that _ The appearance of the disc will at once indicate | if the light required raising or lowering, B had to in what direction the light requires to be moved | be screwed or unscrewed, whilst a side swing in order to get unifonnity. could be imparted by manipulating C. + “Thus, if a shadow be One was introduced by Mr. J. H. Steward, formed on the upper |} Fig. 2 in which the knob A, racked the portion of the disc, | jet up or down keeping it meanwhile quite the light must be | horizontal. By turning B a swing motion is moved downwards; | obtained by which the jet is moved to either ifon thelower portion | side, whilst a forward or backward motion can upwards; if at the | be obtained by turning C. Should the lime not right hand side, to | be at the precise distance from the nipple this is left, whilst the light | remedied by turning D. JE turns the lime, and must be moved more | F actuates a cut off tap—whilst the whole to the right if the ; apparatus after being in correct position as Big. 1. shadow be seen on | regards raising or lowering is clamped on the the left hand side of the disc. two uprights by GG. Then, again, if the light be too near the Jets by other makers have been or are being condenser a bluish shadow will surround the | introduced, by which the same effect may be disc. obtained, although perhaps ina slightly different Many people centre the lime-light ina moment | manner. without any special appliances for so doing, by Messrs. Newton & Co., of Fleet Street, E.C., merely liberating the clamping screw which | have just completed a model shown at Tig. 3. secures the jet to the upright pin, supporting | As will be observed the jet rests upon a stage, the jet by the hand until itis in correct position. | wpon which it is clamped for rough adjustment, On the other hand we have seen people ex| this stage is capable of having the finest adjustperience great difficulty in getting a clear disc, | ment imparted to it from behind, by the two the jet always seemed to move with a jerk, and | milled heads shown at the left hand side—the after it was correctly adjusted sideways would | longer of the two causing the stage with jet to perhaps slip down on the pin and upset the | be raised, keeping the jet meantime in a horicalculation. zontal position. It would appear that the lanternist of the By means of the shorter knob, the jet and present day likes to do all his adjustments by | stage can be moved sideways, thus keeping the merely turning a knob, and there being ademand | nipple, lime and upright always in line with the for jets which can be readily centred by this | optical axis. fi) my f A jet has been patented by —_ Mr. Abm. Kershawof Leeds, which is about the same size as the ordinary commercial jet, can be fastened upon any jet-tray and yet be raised, lowered, or moved from side to side for centreing purposes from behind. The jet, after being roughly centred, is clamped to the upright of the tray by the usual screw A, The portion of the jet which fits Fig. 2. on the upright is composed of two tubes, one of ineans, such have been introduced to meet this | which can be turned. . As A clamps the inner want. { one to the upright, the outer is free to move, were it not kept in position by the screw B, The first jet capable of being centered from ret J : which is fitted with a strong steel spiral spring. behind was the invention of Messrs. Ottway and