The Optical Magic Lantern Journal (June 1892)

64 A SECOND penny photographic weekly has made its appearance. Hitherto Photography has been the only weekly at this price, but Messrs. Piper and Carter, of Furnival-street, E.C., have just brought out Photographic Work, which is ably edited by Mr. T. Bolas. * * ® WHEN giving a lecture on hand-cameras, Mr. W. D. Welford thus summed up the requisite qualities necessary for a hand-camerist, ‘“ He must be of quick perception, prompt decision, and instant action, although at the same time he must be coolness itself.” 2s * * Mr. A. E.Wape, of 177, Walworth-road, S.E., has fitted up a comfortable and commodious darkroom for the use of customers. * ® x THE Repeater Hand-camera described in our issue of August last, and at that time made by Mr. Cusworth, is now the property of Messrs. J. F. Shew and Co., of Newman-street, who have made several improvements, re-christencd it the Repeatograph, and reduced the price from £338. to £2 2s, b * » A NOVEL entertainment was given by a dozen cyclists (from South Molton), at Chittlehampton, on r8th ult. A complete high-class lantern outfit was carried by two bicyclists, and each member of the band carried his own instrument. Theband consisted of *piano, violins, *violoncello, cornet and flutes. Owing to the delicate nature of the instruments marked * they were not carried on bicycles. The performance commenced ten minutes after the arrival of the procession. In our next we hope to have particulars of the patent folding combined lantern support desk and holder for slides employed. * * * In future the meetings of the iHackney Photographic Society will take place weekly, Tuesdays being the day selected. Arrangements are being made to secure premises where the comfort of “club life’? may be obtained. Mr.’ W. Fenton Jones, 12, King Edward-road, N.E., has again been elected hon. sec. s od * On loth and 17th ult., Mr. F. E. Ives, of Philadelphia, gave lectures at the Royal Institution of Great Britain, on “ Projection of Photographs in Natural Colours.” A report of this and also several articles have been crowded out of this issue, The Optioal Magio Lantern Journal and Photographio Enlarger. _ Positions of Lens when Enlarging. A CORRESPONDENT asks us the following question: Given a light, condenser, picture, lens, and screen in such relation to each other that the picture is sharply depicted upon the screen; why, if the screen be farther removed from the lantern, must the lens be brought nearer to the slide in order to focus the image ? The relation of the lens to the slide and screen is dependent upon focus, so it becomes necessary to explain the term. ; When speaking of a lens being of—say, 6in. focus, 6in. from the lens is the distance at which parallel rays entering it will meet or cross the axis, and if such a lens be held in front of a sheet of white paper, and rays from a distant object fall upon it, such object will be reproduced upon the white paper in an inverted form when the lens is held 6in. from it. This is termed the solar focus. Supposing, then, that with the: same lens we repeat the experiment in a slightly different manner, and, instead of using the parallel rays, allow the rays from an ordinary candle, placed 8ft. or oft. distant, to fall upon the objective, and thence on the white paper screen aforementioned. It will be observed that the focus of the lens is now longer than when the distant object was utilised, and the nearer the candle is brought to the lens the longer will be the focus; or, in other words, the nearer the candle is brought ‘the greater must be the distance between the lens and the focussing screen, From this it will be evident that there is some relation between the object to be focussed and the distance of the focussing screen from the lens. The relationship of the two is termed conjugate focus. Were the condenser and objective to be removed from the lantern, and the eye applied a little distance off at the centre of the slide, the margins would not appear illuminated, as light only travels in straight lines; but all this lost light can be utilised by replacing the condensers. The one lens collects the rays which come from the illuminant and causes them to reach the second one of the condensers in a parallel form, whence they converge to the objective. The nearer the light is placed to the condenser, the shorter is the anterior focus and the longer the posterior focus, and if at the point where the latter rays meet, a sheet of paper be held, an image of the illuminant will be seen. The objective in like form has a conjugate focus, but when considering it in connection with the light from the condenser, we have to deal not with the illuminant itself, but with the light