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The photographic news
- Bandzählung
- 7.1863
- Erscheinungsdatum
- 1863
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- SLUB Dresden
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- Public Domain Mark 1.0
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- urn:nbn:de:bsz:14-db-id1780948042-186300004
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- http://digital.slub-dresden.de/id1780948042-18630000
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- oai:de:slub-dresden:db:id-1780948042-18630000
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- LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
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- Parlamentsperiode
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- Bandzählung
- No. 227, January 9, 1863
- Digitalisat
- SLUB Dresden
- Strukturtyp
- Ausgabe
- Parlamentsperiode
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- Wahlperiode
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Zeitschrift
The photographic news
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Band
Band 7.1863
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- Titelblatt Titelblatt -
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- Register Index 619
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Band
Band 7.1863
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india-rubber sticking in a groove, and in another external one, having its corresponding sides parallel, and at the same height on the other side. In this slide there is a second, which plays within the first, and is intended to receive the collodioned plate; it is called the plunyer. because it serves to introduce the plate into the baths by plunging into it. It is formed of bands of copper or of brass, of the same breadth and thickness, soldered together. This slide must be properly silvered. It is moved from the principal slide into the baths, and from the baths into the principal slide, by a cat-gut string passing to the outside by a hole through the upper part of the principal slide. This plunger may be made of vulcanized india-rubber. A spring, of a particular form* adapted to the outside shutter of the slide, permits of a suitable pressure being exercised at will upon the plate placed within the slide. The manipulations with this apparatus are extremely easy to perform. We commence by placing the principal slide containing the plunger upon the nitrate of silver bath ; the slide passes to the opening of the bath, and is stopped by the partition of the bottom at the point of complete coincidence of its opening with that of the bath. We next open the shutter of the slide, and collodion the plate, which is placed in the plunger. Then the shutter is closed, taking care that its spring be properly adjusted; then the stop plate is withdrawn, and the plate falls into the bath. After it has become sufficiently sensitized, it is returned to the principal slide by pulling up the cord on the outside. The opening of the principal slide is now closed by returning the stop-plate to its original position, the bolt of the springs withdrawn, and then the plate is ready for exposure in the camera. To develope the image obtained, the slide is carried to the bath of protosulphate of iron, and operated with as described. For the sensitizing bath, with this difference, however, that the bath is turned on its hinges so as to examine the development of the image by transparency ; the principal slide may then be withdrawn from over the bath on leaving the plunger, which is withdrawn afterwards, so as to avoid staining the principal slide. It now only remains to wash and fix the picture. If necessary, other baths may bo established between those mentioned above and the box carrying the glass plates. Before commencing another picture, the slide must be cleansed of all traces of the iron developing solution. For the movements of the plunger to be perfectly free, the internal space of the principal slide must be narrower than the bath, and the lower opening of the principal slide must be rounded at the edges, and bevelled. The plunger can be dispensed with by employing silver pincers and a screw, to seize the plate at its upper end. We can also employ different hooks. In this new system the plate moves in grooves formed by the shutters of the slide, and two fillets fixed upon the interior surface of the shutter. The baths require no sort of modification. This arrangement can be applied to all kinds and sizes of cameras. M . Icard has communicated the following note upon Graduated Backgrounds:— “ Many contrivances for the attainment of this object have been described, none of which appear to me to be comparable, either in simplicity or in the results obtained, to that which I make use of. The following is a descrip tion of it:—I have made a little groove on each side of my pressure-frame, so as to admit of my introducing a piece of wood which completely masks the plate. An oval, of greater or lesser axis, according to the size of the object to be copied, is cut in the centre of this piece of wood. At the moment of exposing the frame to the sun’s rays, or to diffused light, the whole secret consists in applying a piece of ground glass to the oval: the light reaching the picture only through this ground glass will give a gradation of tone of exquisite delicacy. In the absence of a piece of ground glass a sheet of tracing paper will produce the same effect; the piece of wood can also be replaced by a piece of blackened cardboard with raised edges, fitting the frame exactly like a coverlid.” M . Van Monckhoven has addressed to the secretary of the French Photographic Society the following communication upon the action of light upon certain compounds of silver:— “ In an article contributed by M. Roussin to the Society’s Bulletin, which 1 have just received, I read that ‘Iodide of silver is not necessary in the albumen process in order to obtain images in the camera obscura. This salt only increases the rapidity a little.’ “ I beg, sir, to refer you to No. 173 of the British, Journal of the 1st September last, where you will find this fact stated in nearly the following words :— “ 1st. In Young’s experiment (consisting in the develop ment of an image upon albumen after fixing) the image is not due to the iodide of silver, but rather to the albuminate of this metal. “ 2nd. Every process in which, besides iodide of silver, there is present an organic body capable of combining with the nitrate of silver, will admit of development after fixing. “ 3rd. In these processes the iodide of silver may be omitted in practice. “ The fact announced by M. Roussin is, therefore, a particular instance of the rule laid down. “If, sir, any doubt lingers in your mind on this matter, I beg of you to peruse pages 322, 323 of the fourth edition of my Traite de Photographic, which I enclose. “ In my opinion, the theory of the format ion of the image in the camera may be stated in these terms:— “ 1st. In the processes where the iodide of silver is pure, or mixed with an excess of nitrate of silver, the action of light is purely physical. “ 2nd. But in the processes where an argentico-organic combination exists in presence of iodide of silver, the action is double ; first there is a physical action upon the iodide, then a chemical action upon the organic combina tion. Besides, the iodide of silver is not absolutely neces sary in these processes in order to obtain images in the camera obscura. With regard to M. Roussin’s second asser tion, I have a few words to say—‘On the rapidity which iodide of silver communicates to the albumenized glass.’ I have, in fact, remarked the same thing, but the pro- foundest research has proved to me that this is due to the transparency of the albuminate of silver—a transparency so complete, that the light can impress several plates placed one over the other at the same time. But if the albuminate of silver be opaque (if the film be very thick), then the luminous rays are stopped ; besides, I have not been able to discover in these conditions any difference between the sensitiveness of plates simply albumenized, and those albu menized and iodized.” M . Davanne states, that on two several occasions he has proved that the abundant smoke of tobacco had an influence upon the development of negatives. In one of these instances a colleague attempted an instantaneous process in the presence of several smoking photographers: every nega tive was fogged. Next day he repeated the same process, after the room had been thoroughly aired and ventilated, and the images came out perfect. More recently, himself and a friend developed negatives taken by Taupenot's pro cess, in the same room, with the same materials, and under identical conditions; with the one who smoked the develop ing solution soon became covered with reductions to such an extent that it had to be thrown away; while the other experiment, taken ■when the room was free from smoke, was perfectly successful. Numerous facts serve to prove the truth of these observations; and photographers who are in the habit of smoking in their operating rooms, may rest assured that this is the cause of numerous otherwise inex plicable failures.
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