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THE PHOTOGRAPHIC NEWS. Vol. XXXV. No. 1688.—January 9, 1891. CONTENTS. PAGE Yellow cersu» Orange Light in the Developing Room 17 Backgrounds and Accessories 18 Our Brother the Crab. By James Mew 19 Notes on Portraiture. ByH. P. Robinson 21 Interior Photography. By Lieutenant C. E. Gladstone, R.N.... 22 A Burst Pressure Gauge 24 The Camera and its Various Motions. By Professor W. K. Burton, C.E 25 “Old Masters” at the Academy. By Rev. F. C. Lambert, M.A 28 PAGE Notes 26 Photography in Germany. By Dr. H. W. Vogel 29 Photography in Vienna 30 Literary Notices 32 High Relief Blocks 33 Fire at Messrs. Stone & Co.’s 33 Paten Intelligence 33 Correspondence 35 Proceedings of Societies 85 Answers to Correspondents 36 YELLOW V£RSUS ORANGE LIGHT IN THE DEVELOPING ROOM. As the use of red light in the developing room with plates which are not orthochromatic may now be considered to be a mistake on the part of those who wish, for the benefit of their eyesight, to work in as bright a light as possible, the relative merits of yellow and orange light remain to be considered. The following table by Amedee Guillemin, which we published last week, at once throws much light on the question:— Colours. Luminous Intensities. Lines. Extreme Red ... ... Imperceptible ... ... A Red ... 32 ... B Red ... 94 ... C Orange ... ... 640 ... D Yellow ... 1,000 ... Green ... 480 ... E Blue ... ... ... 170 ... F Indigo... 31 ... G Extreme Violet ... 6 ... H This table shows the relative luminosity of the spectrum where cut by the eight principal lines of Eraunhofer. The maximum brightness is between D and E, nearer D, and distant from it about one-tenth of the total interval DE. The yellow, it will be seen, appears to the eye to be not very far from double as bright as the orange of the same spectrum, therefore orange is a colour to be avoided in developing room operations; but it is a far better colour to use than red. In farther illustration of this principle, we reprint the diagram from the Yeak-Book showing the luminous intensity to the eye of the different parts of a diffrac tion spectrum, and it will be seen that the brightest rays are the yellow, between D and E, fig. 1. Guillemin probably used a spectrum produced by a prism or prisms. Anyhow, the falling off in luminous intensity is so great in the orange as compared with the yellow, that the former ought not to be used. We prefer a full sunflower yellow, not deep enough to be mis taken for orange, and to use a translucent screen. Still, under certain conditions, light lemon yellow can be used with safety. One reason why what is called “canary medium” answers well in some hands is that the fabric is thick, and, in addition, may be used in more than one layer, so that the good trans lucency of the material adds to such safety as is given by the colour. By avoiding the use of too strong a light, by developing at a suitable distance from the screen, and by attending to the conditions we published last week, there is no difficulty in employ ing the canary fabric with safety; indeed, many photographers have for years used it with satisfaction. A fundamental error running through much of the literature of the past, is the recommendation to put an unexposed plate in a slide with the shutter half drawn, then hold it in front of the developing lamp window, expose thereto for five minutes, and after wards pour on the developer to see if it gives fog on H K / X W N Fig. 2. the exposed half. In actual work a plate is practically never so exposed, and should it thus give fog may yet do well for developing operations when the conditions are applied which we published last week. For instance, let A, fig. 2, be the translucent front of the developing room lantern, and H a plate held vertically before it for five minutes, at a distance of nine inches, and suppose the plate to be then slightly fogged. Had it been held eighteen inches off, at K, probably it would not have been fogged, because the intensity of the light there is four times less. Again, it probably would not have been fogged had it been