The photographic news

• Bandzählung: 6.1862
• Erscheinungsdatum: 1862
• 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-id1780948042-186200003
• PURL: http://digital.slub-dresden.de/id1780948042-18620000
• OAI: oai:de:slub-dresden:db:id-1780948042-18620000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
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• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

March 28, 1862.] THE PHOTOGRAPHIC NEWS. 147 862. ATUS fio i, or and suf room o' n ben® y welli he ford (he firs ;ht over passing en thal equivt e room partase general field work, to let their choice be biassed less by the price, the size, the weight, or prettiness of any particular form than by its efficiency to produce good pictures with as few openings for failure as possible. Let portability and convenience be attained by ingenuity and mechanical skill, but never by the sacrifice of any necessary quality. If the price has to be studied, let cheapness be gained by modera ting the ambition to a simple form, without any complica tion of details beyond what is strictly necessary, and to a limited number of duplicate parts. {To be continued.) gin I there was the least movement in the air. n ""me of the early Daguerreotype cameras, the shutters /psled inwards by means of a spring or other contrivance. 8 was abandoned in the idea, I believe, that the aning in this manner raised a dust in the interior, and for ,, 1ong time none have been so made. I am inclined to sink the plan was too lightly abandoned without a snfli- Slent trial. If dust was the only objection, the remedy lay n file photographer’s own power ; he had only to keep his Lnera clean. A shutter opening inwards would of course I perfectly light tight, and would not in any way be 4lected by the wind. Such a shutter could not be adapted to many of the present designs of camera, which pack up ! dryib: thefro As dr mselve cover® s recot” ispens rly w ire, 9 le w therf rt , flyi: nd caw rnets0 is in t ach sid‘ (fig. 10/ light at t entire tippled ngth of lit at b ■ee feet, ut two que by l D dis he only' it seven > direct ground of the slide project slightly over the plate to protect the edges from the light (fig. 10), as without the aid of light these slight impurities seldom produce stains under the action of the developer. I strongly recommend the adoption of this precaution as an important protection against stains upon dry plates. Many plate-slides arc made in this manner, but the generality, I think, expose the whole plate to light. Dor a small camera, th of an inch all round is sufficient, but for large plates which are more handled, and drain in larger quantities, I should advise } inch all round. The sliding shutter by which the plate is uncovered is a very important part of the plateholder, especially for out-of- door photography ; and I do not think we have yet hit npon any form that, when applied to the field cameras, is quite satisfactory in all respects. The principal considerations that bhouldaffect its design are—its capability of excluding all ight from the plate, excepting from the front, when it is raised; and the action of the wind upon it while a picture B being taken. The forms of shutter mostly used are those which open upwards, and lie upon the top of the camera; those which open downwards, and remain at right angles to the axis of the camera; those which open sideways, and re- main stretched out at right angles to the axis of the camera; and finally, those which open sideways and folding forwards lie parallel to and against the side of the camera. I believe the first of these, which is the one most commonly used, is the best, though I am inclined to hope that we shall ulti mately attain one which more completely fulfils the neces sary conditions. I do not think there is any danger of light getting im properly on to the plate with any one of the forms of shutter I have named, if carefully made ; but they all of them offer the inconvenience of being considerably affected, when open, by a very small amount of wind. Those which fold down and lie against the instrument, of course, less than the others. Still, from their thinness, which gives them certain amount of spring, even these catch every little breeze, and create a vibration which is communicated to the whole camera, and tends to destroy the sharpness of the image. My practice, to avoid this as much as possible, is, when I have raised the slide, and before I uncover the lens, to put a stone or other Weight upon the shutter to keep it steady ; but I should be glad if we had a shutter with which such a contrivance was Inecessary. Those shutters which do not fold down, but Ntand out stiff, of course are yet more easily caught by the vind, and as they arc generally slight, and flexible to a cer- tain degree, they chatter and vibrate considerably, and often Very detrimentally. I speak on this point from experience, having had a camera, the slide of which opened in this Tnner,and I had to contrive a stay to keep it steady when- PHOTOGRAPHIC CHEMICALS: Their Manufacture, Adulterations, and Analysis. Sulphides of Arsenic.—Passing over several metallic sul phides which possess no interest to the photographer we come to those compounds, which, owing to their colour, are used in painting. Arsenic forms several compounds with sulphur, the most important being the bi-sulphide, the ter- sulphide, and the penta-sulphide of arsenic, composed respectively of one atom of arsenic with two, three, and five atoms of sulphur. Bisulphide of Arsenic, known also by the names of red sulphide of arsenic, realyar, sandarach, and ruby arsenic, is of frequent occurrence in nature; it is also prepared artifi cially by fusing arsenic with a higher sulphide. It is of an aurora-red colour inclining to brown, when in mass, and yields an orange yellow powder, which becomes red-brown whenever it is heated. It fuses easily, and is not decom posed when heated out of contact with air, volatilizing un changed at a temperature much below a red heat. Heated in the air it burns with a blue flame, forming sulphurous and arsenious acid. Heated with nitre it deflagrates with production of a vivid light. Several brilliant pyrotechnic mixtures employed in night photography are based upon this property. The Indian inhite-Jire is produced by the combustion of a mixture of 24 parts of nitre, with 7 of sulphur, and 2 of realgar. The signal light employed by the English Government is very similar to this, with the exception that a higher sulphide of arsenic is used. It is prepared by mixing nitre 7 lbs., sulphur 1 lb. 12 ozs., orpinent 8 ozs. This is said to be the best white fire known. It must be carefully borne in mind whilst experimenting with these compositions in which a poisonous metal plays so important a part, that the products of the combustion must on no account be allowed to escape into a room, but must pass to a chimney having a good draught. Tersulphide of Arsenic, known also by the names of yellow sulphide of arsenic, and orpiment, is also found native. It may be prepared articially by precipitating an acid solution of arsenious acid with sulphuretted hydrogen, and also by fusing the red sulphide of arsenic with sulphur. There is a so-called orpiment prepared on the large scale by sub liming arsenious acid with a small quantity of suphur. According to Guibourt this is a mixture of C per cent, sulphide of arsenic with 94 of arsenious acid ; the latter may be extracted with boiling water. This preparation is much more poisonous than the true tersulphide, although the latter is a dangerous poison. The colour of powdered orpiment in the native state is lemon yellow; that of the artificial variety has an orange yellow colour, and turns brown when ever it is, heated. It fuses easily and volatilises unchanged if access of air be prevented. The use of orpiment in the pre paration of white fire has been already alluded to. Pentasulphide of Arsenic is formed by decomposing arsenic acid by sulpuretted hydrogen. It is a lemon yellow powder lighter than orpiment, and without any tinge of red. It fuses less ■ easily than sulphur, and after fusion appears darker and somewhat reddish. Besides these definite compounds of sulphur and arsenic there are others which need not be particularly referred to here, as they are of no special interest to the photographer. Every double back should be numbered in plain figures, one corresponding to each plate ; and it will be found a convenience if a small ivory plate be let into each shutter, or some other part upon which the photographer can make in pencil a memorandum of the view taken upon the plate, „ recording the time of exposure, &c., which he may copy into tet his diary at home. 1 0 8. d Before closing these “ remarks ” upon the subject of cameras, at the risk of repeating myself, I would strongly advise photographers, when they select an instrument lor , . J -I 11-D- from t. into a small compass, so isob! the P3 s for t