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
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• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

280 THE PHOTOGRAPHIC NEWS. [June 12, 1863. part developed with pyro, as before, appears considerably less exposed than the one developed with iron. Prom repeated experiments which have given analogous results, I have formed the following conclusions:—First, That under certain conditions formic acid is a decided accelerator in any developer; for instance, when the light is so weak that sulphate of iron will not allow the develop ment to be pushed sufficiently without staining the nega tive ; formic acid, under these circumstances, produces, as I have observed, a striking improvement. Secondly, But that in a good, strong light, the usual developer of iron requires less exposure to produce a satisfactory result than pyro and formic; and that formic acid and iron, with a little acetic acid, is quicker than all. In making these remarks I wish you to understand that all the chemicals used are in good working condition. DEVELOPING AND INTENSIFYING. BY J. C. LEAKE, JUN.* Perhaps no term is more often misapplied than this one, intensity. I am not quite sure if I know its meaning myself; but I think, as applied photographically, it means that quality which will enable the negative to reproduce on paper an impression of the original subject photographed in its correct light and state. This being granted, we will proceed to examine the various processes used to this end. One error seems to me prevails largely among photo graphers on this subject; it is this, that the same amount of brilliancy is necessary in all their productions. Now I venture to suggest that this is wrong, and, that while for many, perhaps most subjects, the more brilliant the lights and the deeper the darks, the better; yet in some cases it will be advisable to diminish the intensity in order to pro duce a softer and more artistic effect. I make these remarks, because as we proceed, you will find I lay down no definite rule as to intensity, but endeavour to explain the tendency of each process named, leaving the application to individual judgment. Some years since, when a simply iodized collodion was used, the impression being developed by pyrogallic acid, no difficulty was experienced as to getting a full amount of in tensity. But the introduction of bromides, and iron develop ment made so marked a difference in the beauty of gradation and the capacity with which pictures could be produced, that notwithstanding it was often found difficult to get sufficient density for printing purposes, the process has come into general use. I am not of those, however, who think the image on bromo iodized collodion developer with iron, is necessarily thin. On the contrary, I believe that, with proper care, an im pression may be obtained of sufficient density to print at once without any intensification whatever, although I do not think it judicious as a rule. If we start by examining the conditions likely to affect the intensity of the image, we shall perhaps be better able to understand the subject. To begin with the collodion; of course, bromo-iodized. The best results will undoubtedly be obtained when it has been iodized at least a week. If the image is thin (as it would be if the collodion were used immediately after iodizing), it cannot readily be brought up to the required strength. It is well to have a good full film, or it will be difficult to obtain a rich, deep negative. But most impor tant of all is the condition of the silver bath. I may as well at once confess to heresy on this point; for notwith standing all that has been said and written to the contrary, my opinion still is, that the presence of an acetate is of the utmost use, both as to rapidity of action, density, and colour of the deposit. The presence of nitric acid, often recom mended to be added to the bath, has a tendency to produce * Read at a meeting of the London Photographic Society, June 11th. a grey metallic deposit, which is next to useless for printing, and very difficult to intensify. If carbonate of soda be added to the nitrate solution, and left in contact with it some hours, it will be found that the image, which before was grey and transparent, is now of a rich brown, much more intense, and capable of being intensified to almost any extent. As might have been anticipated, the length of exposure affects the intensity to a large extent, and it will be found that the best results will be obtained when the exposure has been so prolonged that one application of the developer is sufficient to thoroughly bring out the impres sion. From time to time various substances have been recom mended as likely to increase the density of the image when used in conjunction with the ordinary sulphate of iron developer. After trying a number of experiments, however, I am inclined to think that, as a general rule, a developing solution containing from ten to twenty grains of iron, and the same proportion of acetic acid, will be found to answer for general purposes better than one made according to more complicated formula. At this stage of the process the image should present the following characteristics,—all the details should be well out, the high lights sharp, while in the deepest part of the shadows the iodide should remain unaltered in colour, the whole picture standing out boldly and having a generally “ plucky ” appearance. I am convinced that a great deal of time and trouble is wasted, and many failures incurred (the blame being thrown on the process employed), in trying to intensify pictures which cannot by any process be made to yield a respectable print by reason of their infirmity; and the unfortunate man who has suggested a process for intensifying which answers well in his hands, is consigned to various places as a “ muff,” because that same process will not convert anything anybody may happen to get into a first-rate printing nega tive, without any trouble whatever. So that while I cheerfully admit that “ dodges” may be useful at times, the best “ dodge” will be to endeavour to secure a picture which will require as small an amount of after treatment as possible. There now remains three stages during which the negative may be intensified—before the removal of the unaltered iodide by the fixing agent, after the fixing process, and also after the film is dry. Intensifying, at each of these stages produces a slightly different result. The softest negatives are, as a rule, produced by using ft weak solution of pyrogallic acid and silver before fixing; but it should be remembered that unless very carefully used this process is likely to obscure the delicate detail of the negative by a heavy deposit of silver. If, however, the iodide be removed by fixing, this process with pyrogallic acid is perhaps the safest and most certain now in use, and, doubtless, in good hands is capable of producing the most beautiful results. For my own part, I am inclined to think these two methods may be used in conjunction most advan tageously, a little being done before, and some after, fixing. If the original negative be very thin it will often be found difficult to obtain the requisite density for printing after fixing; but if we intensify slightly before, we shall have but little trouble afterwards in obtaining any reasonable quantity. Before the iodide is removed the intensity seems to be obtained by an actual deposit of silver, but after its removal scarcely any silver appears to be deposited, but the colour of the negative is altered from grey to a rich non- actinic brown. Greatly favouring, as I do, the idea that in tensity by colour is better than intensity by deposit, I think that if a fair amount of deposit can be obtained by iron, and this slightly altered in colour by the after application of the pyrogallic solution after fixing, better and more delicate negatives may be produced by this than by any other Pro- cess ; but it must be borne in mind that an increased ten dency to hardness accompanies all processes used for intensi fying after fixing. It may not be out. of place to mention here that, when it is intended to use this process, the "JP°