The photographic news

• Bandzählung: 29.1885
• Erscheinungsdatum: 1885
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-188500006
• PURL: http://digital.slub-dresden.de/id1780948042-18850000
• OAI: oai:de:slub-dresden:db:id-1780948042-18850000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Seite I-II fehlen in der Vorlage. Paginierfehler: Seite 160 als Seite 144 gezählt.
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

A great deal has been written and said as to exposure in the camera, and tables calculated with a view of arriving at an in fallible mode as to exact time ; but my experience leads me to the conclusion that a particular knowledge of judging by sight, assisted by the appearance on the focussing glass, is the only way to determine the true period, except in such instances as interiors and deep gorges, where the actinometer is requisite. The actinic force of light is constantly altering from morning to evening of each day, and the quality is also completely changed at different seasons of the year ( April and May being by far the best months in this respect), and a knowledge of judging accurately as to its value can only be arrived at by observation of the state of the atmosphere. A successful photographer must be one having talents artistic, chemical, optical, and mechanical—combining great energy and resource to discover the requisite elements to make up a first- class picture. One of the special aims of this Association should be the education of its members, a field too large to be entered upon in my address. The time has arrived when an effort will be required to pro duce an apparatus of a portable character to enable us to change or develop our plates without a dark-room. The necessity of this is especially felt upon a voyage or in foreign countries, where con venient places are sometimes very difficult to find, and also at home, where an .entire room cannot always be set apart for such a special purpose. I have endeavoured to meet this want with the models I now bring before your notice, and any suggestions the members may make for their improvement will, I need hardly say, be gladly received. The apparatus which I present is divisible into two parts, and a whole-plate size, when folded together for convenience of portability, only occupies a space of 16 inches long by 12 inches wide by 3 inches deep. The lower portion may be used for the changing of sensitive plates without the chance of being affected by the light. When developing is required, the lower portion is occupied with a piece of thin silvered fluted glass placed at an angle of 45 degrees; this sends the light (one end being open) through a piece of ruby glass lying horizontally above it, upon the upper portion of which is a wooden frame-tray with glass bottom, into which receptacle the sensitive plate is placed for development. The space is sufficiently large to take in the dark slide, which may be manipulated through india-rubber apertures at each end; two pieces of ruby glass on top and side give ample illumination for watching the development of the plate underneath. For travellers visiting distant countries it is hoped that such an apparatus will alleviate the miseries of makeshift dark rooms ; while for those working at home, it would enable them to surmount the difficulty of want of space to which I have just alluded. IMPROVED DEVELOPER. BY PROF. II. W. LORD. Assuming, as is probably correct, that the rapid deterioration of the mixed ferrous oxalate developer is due to the accumulation of ferric oxalate in the solution—this being a most powerful re strainer—and also believing the major part of this oxidation is due to the air rather than to the plate under development, it occurred to me that by adding some substance to the mixed deve loper that would protect it from the action of the air, and even, perhaps, reduce the ferric salt as fast as it formed, the “ life ” of the mixed solution might be greatly prolonge J, and its efficiency increased. The most available substance seemed to be sulphite of soda, which has been so extensively used in connection with pyrogallic acid, but not heretofore, as far as I am aware, tried with ferrous oxalate. My experiments with this salt fully confirmed this opinion. I find that by the addition of sulphite of soda and some fiee acid, so as to slightly liberate sulphurous acid, a permanent oxalate developer of great power is produced. My formula is as follows:— To a saturated solution of potassic oxalate, 175 c.c. (2,975 minims), add 10 grammes (154 grains) of sodic sulphite (crystals); when this is dissolved in the oxalate solution add 50 c.c. (850 minims) of a saturated solution of ferrous sulphate, then add strong sulphuric acid, drop by drop, till a faint odour of sulphur ous acid is developed in the solution, about 1 c.c. (17 minims) is required. This completes the developer. It is very powerful. It can be used over and over again with very little loss of strength. My plan is to mix about 500 c.c. (8,500 minims), keep it in a corked bottle, and take out what I want to use. After develop ment, I pour it back into the bottle and shake it up. The next time I want to develop a plate, I take out what I want as before. This developer is too strong for many purposes, so that for most cases it is well to dilute it as given with its own volume of water ; the diluted solution being kept as before. In case of over-exposure, I use but one plan for all developers, viz., take the plate out of the developer at once, and place it in a one-half per cent, solution of potassic bromide for from five io sixty seconds, according to circumstances, then wash off rapidly, and proceed with the development as at first.—Photographic Times. Uorrespondence. CARRIERS FOR DOUBLE DRY PLATE BACKS. Sin,— The following may not be new to many of your readers ; but if you think it would be useful to some, you will perhaps give it a corner. Wanting to use some double dry plate backs for smaller plates than they were made for, I found I could not get carriers made in wood, as there is not more than 1th inch space ; so I procured a piece of material known as vulcan ized fibre, the flexible kind, made in sheets and |th inch thick ; this can be cut to the greatest nicety with a sharp strong large blade of an ordinary penknife, and a straight edge, and I soon male the carrier I required, using a small piece of the waste centre split in half to form the corner supports. The material, though flexible, is rigid enough for, I should think, a 12 by 10 camera; the size I have made is 9 by 7. The corners are glued on, and the whole cost less than Is. As the material is only 2s. per lb., and not brittle or hard like ebonite, anyone can make these carriers easily; vulcanized fibre will not stand much mois ture or acids, and can be bought of the agents, Messrs. Mosses and Mitchell, Chiswell Street, E.C.—I am, sir, yours faithfully, Frank HAEs. LENSES FOR TAKING SMALL PICTURES FOR SUBSEQUENT ENLARGEMENT. Dear Sir,—Mr. Parr’s question in your last involves a very large subject. It is not only the covering or depict ing qualities ot lenses which are concerned, but the whole range of outdoor photographic work. To avoid on the one hand monstrous foregrounds, and on the other diminished or invisible distances, is not a matter involving judgment merely as to lenses. Both are faults specially incident to the use and abuse of lenses of wide angle, and therefore of short focus ; but while the first fault may often be cured by a judicious use of the rising front, and, perhaps, a lowered stand, the other is inherent, depending directly on the focal length. How rapidity has barred the way to long focus up to a recent date, I really do not know, and cannot there follow the argument. Twenty-five years ago long focus lenses were more used than now. For myself I value greatly the opportunities afforded by a large choice of lenses of exercising my judgment in choosing the best point of view for each subject, and subordinating, not the view to the lens, but the lens to the view. But I will say that if really confined to one lens, I should probably prefer a wide angle rectilinear doublet made for plates the next size larger. I am inclined to think that the superiority of the best lenses of this description in flatness of field and marginal definition, over the more rapid doublets, is less commonly appreciated than it should be. Even a single lens from a good wide angle combination will cover better with a small stop, than a rapid doublet of the same focus similarly stopped down. On the other hand, these advantages become less sensible in very small sizes. And, again, a very rapid doublet is often the best for instantaneous views ; and such are the most tempting subjects for enlargements, especially to