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The photographic news
- Bandzählung
- 15.1871
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- 1871
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- Englisch
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- Hochschule für Grafik und Buchkunst Leipzig
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- Hochschule für Grafik und Buchkunst Leipzig
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- Parlamentsperiode
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- Bandzählung
- No. 658, April 14, 1871
- Digitalisat
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Zeitschrift
The photographic news
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Band
Band 15.1871
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- Titelblatt Titelblatt I
- Sonstiges Preface III
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- Register Index 619
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Band
Band 15.1871
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- Titel
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THE PHOTGRAPHIC NEWS. Vol. XV. No. 658.—April 14, 1871. CONTENTS. PAGE E1 A Simple Method of Intensifying.—The Action of Light on Unfixed Negatives 169 Splitting of Films.—A New Cause 169 Proportion of Chlorides in Collodio-chloride of Silver 170 Echoes of the Month. By An Old Photographer 170 The Purpose and Limits of Retouching. By W. Hartmann ... 171 The Autotype Process. By Tom Taylor 173 Coffee and other Dry-plate Processes. By A. De Constant 174 PAGE Children in the Studio. By Isaac Wilde 175 Weights and Measures in Continental Formulae 176 Correspondence.—Photographs at the International Exhibi tion—Splitting Films— Victoria Card Albums— Photo-gal- 177 Proceedings of Societies.—Photographic Society of London 179 Talk in the Studio 179 To Correspondents 180 A SIMPLE METHOD OF INTENSIFYING.—THE ACTION OF LIGHT ON UNFIXED NEGATIVES. . A pew years ago, Mons. Blanquart-Evrard published an interesting little pamphlet on the intervention of art in photography, one of the chief aims of which was to indicate a method of strengthening a negative in some parts only. The plan indicated consisted in submitting a developed, but unfixed negative, to the action of light, masked in the parts intended to remain unchanged, and exposed in such parts as required additional intensity. The action of light on the negative in this stage was to continue reduction, and increase intensity. The fact that light continued reduction of silver in an unfixed negative was not unfamiliar to experienced photographers ; but the idea of utilizing this fact appeared to have occurred first to M. Blanquart-Evrard. Oddly enough, after the fact was pointed out, it does not seem to have attracted much attention, nor to have been made available in general practice. We gave details of the ; process as described by the eminent Frenchman at the time, and verified the method he suggested of utilizing the idea in the local intensification of negatives, but we do not remember to have seen this mode of intensifying used on a single occasion until a few days ago. During a recent visit to the studio of Mr. Blanchard, whose portraiture, as many of our readers know, approxi mates more closely to the work of Mons. Adam-Salomon, the prince of portraitists, than that of any other photo grapher, we enquired details of some of the formul and modes of working in use at the moment in producing some very large portraits of rare excellence. Mr. Blanchard has SO fully described in our pages and at meetings the processes and formulae he employs, that we anticipated the reply to the effect that everything was old and well-known, “ except,” said Mr. Blanchard, “ perhaps, the mode of in tensifying I am just about to adopt, which is probably less familiar than it ought to be.” The plan in question simply consisted in placing the negative, after development with iron and washing, but be fore fixing, in direct sunlight for a few minutes, during which time a very definite but delicate change took place. As Mr. Blanchard explained, he very rarely required to in tensify his negatives at all, simple development with iron being sufficient; but if any tendency to flatness were noticed in a negative after development, or any want of brilliant points of high light, a few minutes of sunlight afforded the simplest and surest mode of securing the end in question. The process evidently consisted in a further re duction of such traces of free nitrate of silver as remained in the film, that reduction being only effected where the free silver was already in contact with a reduced portion forming a part of the image, and not at all on the deep shadows where no reduction had already taken place ; and further, the reduction was most rapid and complete in the highest lights or densest parts of the negative. Mr. Blanchard added, that where considerable intensification was necessary, few methods of securing it were more satisfactory, simple, and certain than allowing the unfixed negative to remain some time in the sunlight, drying there, and being fixed subsequently. The question not unfrequcntly arises in relation to field manipulations, “ Is it safe to examine the unfixed negative by open daylight?” We have generally recommended caution in doing this, chiefly because, in the usual scarcity of water, and consequent partial washing, the abundant presence of free nitrate on the plate might cause a risk of general reduction and fog. The experience to which we have just been referring suggests that, after a moderate washing, or after treatment with golden syrup solution, the unfixed negative will not suffer risk when exposed to day light, as the reducing action of light is induced chiefly in those parts where reduction has already taken place, and that an increase of intensity, greatest in the highest lights, is the result to be anticipated. SPLITIING OF FILMS.—A NEW CAUSE. In the contribution of an “ Old Photographer ” on another page, a pertinent question is asked in relation to the split ting of films. He suggests that whilst all the varied suggestions as to the quality of the collodion, the kind of varnish, the conditions of keeping, may possibly have some definite relation to the cracking of films, it is quite certain that there is something beyond which remains to be dis covered ; otherwise, how is it, he asks, that in a batch of nega tives taken with the same collodicn, varnished with the same varnish, and kept under the same conditions, some will crack, and others remain perfect ? That this is often the case photographers know, and, being so, it seems difficult to affirm that the collodion, or the varnish, or the keeping conditions, which prove good in many cases, should be the cause of splitting in other cases. It is clear that some other cause—or, at least, some other predisposing conditions— must come into operation in one case which are absent in the other. Collodion, varnish, and mode of keeping may each tend to produce the fault just when they concur with some other accidental cause, but may be perfectly trust worthy under other conditions. A letter from a correspondent on another page suggests the possible action of acetic ether formed in an old iron developing solution. But acetic ether, although a solvent of pyroxyline, scarcely, we think, exercises much action on
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