The photographic news

• Bandzählung: 11.1867
• Erscheinungsdatum: 1867
• 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-id1780948042-186700008
• PURL: http://digital.slub-dresden.de/id1780948042-18670000
• OAI: oai:de:slub-dresden:db:id-1780948042-18670000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

January 11, 1867.] THE PHOTOGRAPHIC NEWS. 15 ORGANIC DEVELOPING POWDER. Dr. Sonxauss, in the Photographisches Archiv, gives the results of analysis of a new “ organic ” developing powder, stated to be manufactured and sold in England at the rate of three shillings and sixpence per pound. The powder is of a brownish yellow colour, and consists of very fine particles. When required for use, it is dissolved in hot water, in the proportion of three parts of the powder to orty parts of water, to which are added, after the solution las been filtered, two parts of glacial acetic acid; the uantity of the latter must, however, be varied, according to the temperature of the atmosphere, the action of the developer being greatly accelerated by augmenting the proportion of the acid. The developer is recommended to be prepared a few hours before its employment. The following are the results of a qualitative analysis of the powder:— 1. Sulphate of iron and ammonia (the principal con stituent). 2. Basic sulphate of peroxide of iron. 3. Sulphate of copper. 4. Acetate of soda. 5. Formiate of soda. 0. Milk sugar. The proportion of milk sugar contained in the powder is about a fourth of the quantity of sulphate of iron and ammonia. The powder has been skilfully prepared with materials known to produce the best results as developers, the excess of oxide of iron forming, with the acetic acid, basic acetate of peroxide of iron, a compound which has long been known as a powerful developer. Practically, Dr. Schnauss states, the powder gives very good results; it develops somewhat slowly, but with great clearness and vigour. It will be remarked that, although the materials are here indicated, and their fitness for their work confirmed, no formula is given ; and justly so, as, if the preparation works well, the preparer is entitled to any advantage accruing from its sale. cess no element of beauty is lacking. Every gradation in the finest negative is rendered with perfect delicacy; great brilliancy is secured without harshness; every tint of monochrome possible to the painter may be obtained in these prints ; by varying the proportion of colour added to the gelatine, vigorous prints may be obtained from weak negatives; and the surface is free from the gloss which is so offensive to the taste of many. Simplicity, practicability, and economy, are qualities each greatly dependent upon each other, and their exist ence in the process will be shown in the practical details which appear on another page, and ascertained by experi ence. But we may explain, that by simplicity and practica bility we mean that the object of each operation in the printing is perfectly clear and well understood ; that each step in the process follows the others in regular and unvary ing sequence ; and that all the manipulations are easily performed. There is no complexity requiring unusual intelligence to understand, and there are no uncertain con ditions in which success is left to chance or guess-work. On the score of economy, whilst the manipulations are more numerous than those of silver-printing, and the time con sumed probably a little longer, yet, as the materials are much less costly, and the sensitiveness so much greater that three carbon pictures can be printed in the time required for one silver print, it is probable that, on the score of economy, the balance will be found on the side of carbon-printing. It is on the score of permanency, however, that the new process possesses the strongest claims. It is unnecessary to discuss the amount of permanency beloging to silver prints. Under the most favourable circumstances their stability is known to be doubtful. What, then, is the basis of the claim to permanency made for carbon prints? We will state the grounds for such claims. The image is formed of carbon, or, for variety of tone, of some other pig ment known to be permanent. The vehicle in which the colouring matter is held, is gelatine rendered insoluble— converted, in fact, into a substance resembling leather—by combination with the permanent sesqui-oxide of chromium. The adhesion of the image to the paper on which it rests is secured by a thin layer of gelatine, rendered insoluble by the action of the sulphate of alumina. The whole com pound layer of gelatine, colour, and chromium scarcely exceeds in thickness the amount of gelatine on a sheet of well-sized writing paper. The print may be fairly assumed to possess as secure a tenure of permanency as an Indian-ink drawing, to which experience enables us to assign a stability of at least a few centuries. If we have fairly stated the advantages of this process— and we do not think we have overstated them, our conclu sions being drawn from extended experiment and very care ful examination of the subject—carbon-printing, as proposed by Mr. Swan, has claims upon the attention of photo graphers not possessed by any other printing process in existence. We have more than once stated details of manipulation in these pages, but we have pleasure in the present number of laying before our readers a brief statement of the opera tions by Mr. Swan himself, to which we call the attention of our reader’s. THE DIFFUSION OF FOCUS QUESTION ONCE MORE. IMPORTANT as the question of diffusion of focus is, we had fancied that the discussion on the subject had been well- nigh exhausted, and that we should not need at present to refer to it again. Much as has been said and written, we find, however, that there are still some confusion of idea on the subject, and some singular misconceptions on our teach ings concerning it, which we are concerned to rectify. We find illustrations of this confusion and misconception in a leader and in a letter in a contemporary journal. Because we have advocated the diffusion of focus so as to define suf ficiently all planes, it is assumed that we condemn sharpness altogether. We will very briefly endeavour to rectify the misconceptions concerning the matter. The writer of the letter in our contemporary, after refer ring to our article of June, 1861, advocating the use for portraiture of lenses possessing diffusion of definition, asks how it is that in January, 1862, we referred to sharpness as one of the good qualities of a photograph. Wo will give the whole passage of which he quotes part. Reviewing the progress of the preceding year, we recognized a growing appreciation of good qualities in pictures, and said :— A few years ago, if a picture were clean, and sharp, and bril liant, it was unhesitatingly deemed to merit praise as “ excellent photography.” If it were out of focus, blurred, hazy, and not at all made out, it was deemed “artistic and suggestive.” Now, however, a picture, to merit the praise of being good photography, or of being artistic, must be something more than either of these we have described. A photograph, to be good and artistic, must be soft and properly graduated, as well as sharp and brilliant; it must be made out, and properly defined in all its parts, as well as atmospheric; it must be harmonious in tones and balanced in forms. No immense patch of white paper for a sky, cut. from the landscape by a hard horizon, will now satisfy the aspiring photo grapher, &c., &c. It is assuredly not for the purpose of vindicating our consistency that wo notice the letter of this correspondent. Were it so, and were there any want of consistency in the two articles, it would be a sufficient answer to state that the above passage manifestly refers to landscapes; whilst our advocacy of diffusion of focus refers chiefly to portraiture, and to add, that a photograph could not be “ properly graduated ” if it were defined only in one plane.. We notice the matter, however, because such a singular misconception