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
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-186300004
• PURL: http://digital.slub-dresden.de/id1780948042-18630000
• OAI: oai:de:slub-dresden:db:id-1780948042-18630000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

[March 6, 1863. seconds for a portrait of medium size made with an objective of 4 inches diameter: nevertheless, the proof came oiit well, full of detail in the shades ; and if there be not, as I am, how ever, tempted to believe there is, acceleration in the time of exposure, I can say that this developer acts as rapidly as the ordinary solution of sulphate of iron in the best con ditions. It has an advantage over the latter in not being decomposed under the influence of the atmosphere, the double sulphate of iron and ammonia being much more stable than the ordinary sulphate, and, therefore, admits of a more precise formula. The sulphocyanhydrate of ammonia has also been tested as a fixing agent: — Firstly, for negatives, employed in a saturated solution, it was sufficient topour it upon the nega tive to perceive the layer of iodide of silver disappear as rapidly as when we employ for the same purpose a solution of cyanide of potassium of the strength of 3 per cent.; but it presents the advantages over the cyanide of not being poisonous, of not exhaling the cyanhydric odour, and if the negative has been badly washed and still retains salt of iron, instead of the greenish blue film which is precipitated on contact with the cyanide of potassium, sometimes straining the pictures, we only see the liquids take a red blood colour which disappears upon being simply washed. I have also experimented with the sulphocyanhydrate of ammonia for fixing positive proofs; this substance is an energetic solvent of the salts of silver, and I feared to see that it would act like the cyanide of potassium in corroding the proof; but such was not the result, this fixing agent respected the half tones as much as the hyposulphite of soda does, and appeared to act like it in the different phases of the fixing; the proof must, however, be toned deeper than usual, because it more readily returns to its red colour. This first experiment at fixing, made hurriedly, under unfavour able conditions upon positives which had been some time printed, has, nevertheless, sufficed to show that wc can succeed with it, and I think that by studying it carefully, we may obtain as good results as with hyposulphite of soda, over which the sulphocyanhydrate of ammonia presents the advantage of not giving spots while fixing, and especially of not giving free sulphur, which seem a guarantee of per manency for photographic positives.—Bulletin de la Societe Franqaise ON THE DECOMPOSITION OF TANNIN PLATES. BY STEPHEN P. LEEDS. At the last meeting of the Photographical Society I pre sented to the notice of the members some tannin plates, which were prepared in the latter part of April last, strictly according to Mr. Russell’s process—with the exception that the plates were coated with albumen, diluted with 3 parts of water to 1 part of albumen—and which were taken by me to Mexico, and exposed there in the camera, during the months of August and September, and brought back to this city, and developed during the present month. These plates presented such a novel appearance upon being de veloped, that I deemed them worthy of exhibition, in the hopes that the mystery of their strange appearance might be explained. Throughout the surface of the plates, there appeared ring like spots, some not more than one-tenth of an inch in diameter, while others were about half an inch in diameter. These spots were nearly clear after development. At first I was inclined to attribute the defect to the developer, but the otherwise perfect character of the negative at once refuted any such theory. That the plates were perfectly prepared, is proved by the fact that some of them were tried previous to my departure, and were found to be free from blemish, and to work well. Also that one of them was exposed in Mazatlan, and developed on the same day, and was perfectly clear and clean. Some of those which re mained undeveloped were placed in the bands of some of the members of the Society, and under their treatment pre sented the same appearance; in one case, rather more so, than those which were exhibited by me. I have arrived at the conclusion that a decomposition of the coating of the plates takes place after exposure to light, and that when the development is delayed for too long a time, the decomposition will have progressed far enough to ruin the negative. The plates should, therefore, be developed as soon after exposure as can be conveniently done. The time that can be allowed to elapse between exposure and development, without deterioration of the plates, depends upon so many contingencies, such as power or force of light, quality and condition of plate and tem perature, and dryness, &c., &c., that no fixed rule can be given for it; but I think that not more than ten to fourteen days should ever be allowed to elapse; although I have known plates kept successfully six weeks before develop ment. I have deduced the above conclusion from the facts, that the plates when first prepared and tried proved good ; that the plate, which was exposed, and soon after developed in Mazatlan, also proved good; while those in which the development was delayed for a long time, were all spotted. Two rules may be safely followed—in fact they should be, viz.:— 1st. That the plates, when exposed in the camera, should be entirely free from moisture. 2nd. That after exposure no more time should elapse than is unavoidable previous to development. I am apprehensive that the moisture of the climate may have dampened the plates at the time of exposure. Why the decomposition should have taken this peculiar form, instead of pervading the entire surface of the plate, and what is its primary cause, are subjects I am now investigating, and should my experiments lead to anything conclusive, you shall have the results. I shall leave for Mexico in a few days, and shall take a good supply of tannin plates with me, and shall watch this matter with very close attention. There is difficulty in the way, somewhere, and, if possible, I will ferret it out. In the hope that these few hints may lead others in the right direction, and perhaps elicit an expression of their views upon this, so important a subject, I leave the matter with a promise to refer to it at my earliest opportunity.— American Journal. ON COMPOSITION PHOTOGRAPHS. When will the world become wiser on the subject of photo graphy ? Perhaps of all arts the photographic has been the one most misunderstood, and the one on which the largest portion of ignorant criticism has been written. In its earlier days, portrait-painters took fright at the facility it possessed of affording a really truthful representation of life, and, fearing their own art would suffer, did all in their power to decry the latest-born of science, and abused it as a mechanical method of producing a map of the face, having no power of giving a life-like presentment of the human face divine. The beautiful results exhibited by our best professors have, in some measure, removed this erroneous impression from the mind of the public, and the press has tardily given way in this matter to the voice of the many; but it is still curious to notice the rabid manner in which some of the writers of criticism in the daily papers oppose the introduction of fine art into photography : they still speak of the camera as an unthinking machine, forgetting that the machine, as the brush of the painter, is guided by the will of the operator. As a specimen of this kind of criticism, one may mention the review of our present Exhibition by the Daily News. The writer says—“ If there is a development of the photo graphic art more offensive than any other, it is that in which the aim is to make a subject-picture by ‘ arranging,’ as the phrase is, so many properties and living lay figures as a picturesque composition. There is one particularly conceited attempt of this kind (IGO, ‘ Bringing Home the May’) by