The photographic news

• Bandzählung: 13.1869
• Erscheinungsdatum: 1869
• 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-id1780948042-186900000
• PURL: http://digital.slub-dresden.de/id1780948042-18690000
• OAI: oai:de:slub-dresden:db:id-1780948042-18690000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Heft 545 (S. 73-84), Heft 547 (S. 97-108), Heft 589 (S. 599-610) fehlen in der Vorlage. Paginierfehler: Auf Seite 444 folgt Seite 443
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

May 14, 1869.].' THE PHOTOGRAPHIC NEWS. 233 OVER-DEVELOPED NEGATIVES. BY M. CAREY LEA.* Almost the very last thing that a photographer learns is, the exact point at which to stop development. It is easy to give a criterion to fix the point ; the difficulty lies in acting up to it. To get the most perfect combination of brilliancy and softness, one should develop just as long as transparency remains in these denser portions of the image which are to constitute the high lights, so that the very central spot, as it were, of the highest light shall print white. But then this must be a mere point, smaller than a pin’s head. Just as soon as this point widens out a little, we get that repulsive chalkiness that leads the careful photographer to consider the negative as worthless. The difficulty in hitting the right point lies, not merely in the needful experience of what the negative should be, but in judging it under difficulties. The light in the operating room is often insufficient, but even if abundant, its colour is unfavourable, and the negative itself is, to some extent, blocked up by the undissolved iodide and bromide. Besides, the fixing bath varies in strength, and acts differ ently upon different films, so that at times more, and at others less, reduction of strength occurs in the fixing. Experience and close observation remove these difficulties to a large extent, but not altogether, so that, after a succes sion of good results, there will be, from time to time, made a negative in which too much attempt at brilliancy has been made, and which, when viewed after fixing and by ordinary light, gives evidence of something like blockiness in the high lights. In work done at home it will generally be best to try again. But even then the discovery may come too late, and, in views exposed at a distance, we have not this remedy, and in either case must see wh at can be done with the negative. I take it that a careful photographer, when such mistakes do occur, will find them out before he varnishes the nega tive. Not, perhaps, in trying new methods, or in working new sorts of dry plates, in which often the actinic trans parency and opacity are very deceptive, but, in any regular work habitually pursued, the exercised eye will always detect this defect before varnishing. If not, then very troublesome operations of darkening parts of the back may need to be tried. Varnish coloured yellow with alcohol, solution of annatto, of dragon’s blood, or of gamboge, may be tried, perhaps, with advantage, though the writer has never had much satisfaction out of this sort of operation. But, in the much more common cases, where the trouble and its extent are perfectly perceived and measured, as soon as the negative is carefully examined by ordinary light, much may be done to help it. I shall glance rapidly at some of the methods that have been used, before speaking of that which has seemed to me to work best. Cyanide of potassium has been long used for this purpose. It is certainly not a bad agent, except for its poisonous properties, which alone should cause its rejection. But it eats away the half-tone too much, and, whilst the negative is benefited in some respects, it is seriously injured in others. Acid per-nitrate of mercury will actively dissolve the image, and has been used for reducing negatives. It acts powerfully, and should be applied very carefully. All mercurial solutions are objectionable to this, that they seem to render the film tender. Iodizing the film has been used by some. When a nega tive is placed in a weak solution of iodine and water, or to dilute “Lupol’s solution” (iodine dissolved in iodide of potassium), it darkens a good deal, and then lightens again. In this condition it is much more transparent than before. The reduction can be increased by dipping into weak cyanide or hyposulphite. But even without this last, the reduction in strength is apt to be too great, and the bril liancy of the print is gone. Perchloride of iron, recommended first, I believe, by Mr. * Philadelphich P^LOtographer. Hughes, is, to my mind, the most satisfactory agent for this purpose. I do not mean to speak too positively, for I have not often'had to use these means; but the experience which I have had has been altogether favourable. The advantage has seemed to be, that a transparency was put into the densest portions before the half-tone was seriously injured, so that by stopping in good time, the negative was got into a really useful condition. This substance can be had from any druggist, under the name of “ muriated tincture of iron,” in the form of a buff-coloured solution, which, before using, should be largely diluted with water, perhaps ten-fold. The nicest way to apply it is as a bath. The negative should be well wetted, and then plunged into the bath. Frequent examination is necessary, in order to enable the operator to stop at the exact point, and without overdoing his work. When this point is reached, the film must be well washed off, dried, and varnished, and the solution (filtered if necessary) will answer again and again. The method is areally serviceable one, and I think that any one who tries it carefully once, will be disposed to resort to it again should occasion occur. As a matter of precaution, the first trial is best made with a negative of no very great value. HOW TO KEEP A BATH IN GOOD WORKING ORDER FOR THE GREATEST LENGTH OF TIME. BY GEO. H. FENNEMORE. Every photographer who values his reputation should have at least two negative solutions: one at rest while the other is being worked. My plan is as follows:—My negative solu tion is 40 grains to the ounce in strength ; I keep it up by adding, every evening after work, sufficient solution, 60 grains strong, to make up for the amount of solution drawn from the bath during the day. The bath is always kept covered to keep out dust, &c., and a strip of clean filtering paper drawn over the surface of the solution in the morning, before work, to remove any scum or other matter that may have formed on the surface of tl e solution during the night. In this manner your bath may be kept clean, and of suf ficient strength, without the trouble of filtering every day. But if your bath is small, I recommend filtering every night after work. My bath holds three gallons of solution, and this I use three or four days, according to the number of plates dipped therein. It is then taken out, and set in the sunlight until the other is ready to come out; the first is then taken in, filtered, and strengthened if necessary, and takes the place of the one taken out. This routine is fol lowed until they show signs of having excess of alcohol. In that state, before putting it in the light, it is evaporated to one-half its bulk, in a porcelain dish, the quantity made up with distilled water, and then set in the sunlight as before. When it shows signs of pinholes, treat it as recommended in a former article. I never wait for a bath to show signs of exhaustion before taking it out, but feed it every day, and for three or four days’ work give it as many days’ rest: therefore my bath seldom troubles me. In answer to the question as to what developer I consider best, I answer emphatically, iron ; and that without any organic addition whatever except acetic acid. I have tried almost everything that has been recommended in the shape of “ sugars,” gela tine, albumen, candy, &c., and find them very useful for some purposes, such as copying, making transparencies, &c. ; but for portrait negatives I think nothing equals plain iron and acetic acid. The strength of the developer should always be deter mined by the results you wish to get. My developer varies from 15 grains to 60 grains strong, but my average developer is 30 grains ; this is used for subjects in general. But there are many subjects that require different treatment; for instance, a person with fair complexion, light hair, eyebrows, &c., should have a weak developer, because that increases contrast, while, on the