The photographic news

• Bandzählung: 35.1891
• Erscheinungsdatum: 1891
• 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-id1780948042-189100009
• PURL: http://digital.slub-dresden.de/id1780948042-18910000
• OAI: oai:de:slub-dresden:db:id-1780948042-18910000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

THE PHOTOGRAPHIC NEWS. [FEERUARY 27, 1891. PLATES FOR HELIOCHROMY. BY GABRIEL LIPPMANN, MEMBER OF THE INSTITUTE, PROFESSOR OF THE FACULTY OF SCIENCES, PARIS. Every grainless plate I have tried has been found to answer. For instance :— 1. Common albumen plates, but it is best to have the coating of albumen thicker than usual. 2. Taupenot plates, with a double or triple layer of albumen. 3. Gelatino-bromide of silver prepared as follows:—In one hundred grammes of water dissolve ten grammes of gelatine, and half a gramme of bromide of potassium. Filter, spread on glass, and let dry. Sensitise more than five minutes in a twenty per cent, solution of nitrate of silver, with a little acetic acid ; wash and dry. Develop with pyrogallol and sesquicarbonate of ammonia, in the same way as Taupenot plates. Wash with water, then with slightly salt water. Fix. THE CAMERA AND ITS VARIOUS MOTIONS. BY PROFESSOR W. K. BURTON, C.E. Chapter VI.—DARK Slides, Changing Boxes, Roll- Holders, etc. Dark Slides.—As in the case of the camera, so in that of dark slides, I should incline to put absolute light-tight ness as the first essential. It is scarcely necessary, in treating of appliances for landscape photography of the present day, to consider other than double dark slides, and these may be classified as slides that open in the middle, book form, the slide being thus opened for inverting the plates, and slides that do not thus open, the plates being inserted from one side, or from the end. It is the rule, in the case of the former kind of slide, that the shutter does not draw out entirely, but only far enough to uncover the plate, and then doubles back with two hinges, so that it will not catch the wind, or be in the way; in the case of the latter, the shutters generally draw out entirely, what may, perhaps, be called a valve closing across the opening left by the shutter. The former kind of slide has, at all times since double dark slides were first introduced, been the favourite in England; the latter has for long been preferred in America. It is a matter of opinion which kind of slide is to be preferred. I confess, without hesitation, that I prefer what is commonly called the “American pattern,” which does not open book-wise, but is so made that the plates are both inserted from one side, a sheet of blackened tin or zinc going between them. The advantages that I have found are greater lightness, and less danger of leakage of light; whilst I have often found the shutter, drawn from the slide just at the time of exposure, to be very useful as a sunshade for the lens. The only objection that I know to this form of dark slide is that the plate that is last inserted, at least, cannot rest against a rebate, but must rest, at one end, at any rate, against small, metallic movable catches, and that the result is a possible slight want of register. With carefully made slides, however, this possible lack of register is so small that it is not of any consideration in thejcase of landscape work. It is commonly said that the American pattern of slide is good enough for small sizes, but that it is of no use for those of large size. I cannot speak as to ven/ large sizes, but I can state that, nearly ten years ago, I had three 12 by 10 slides of the kind in question made by the elder of the two Messrs. Collins, who has died within the last few years, the shutters being made of three veneers with grain crossed; that these shutters, in spite of the very roughest usage, served me well for some six or seven years, and that although, after that, they passed from my hands, I know them still to be in good condition. In America, vulcanite—a sort of thick cardboard—or some times ferrotype plate, is generally used for shutters. Even when the “book-shaped ” form of dark slide is used, I advise that the black opaque sheet of metal that separates the plates be not hinged to the dark slide, but be loose. It is thus possible to use carriers for two plates of smaller size than that of the dark slide, both plates being inserted from one side, an opaque sheet of the size of these small plates going between them. I consider that such a double carrier is to be preferred to two single carriers, as the latter have to be made so very thin. Metallic dark slides have, of late, come much into use. The chief advantage that they offer is that, whilst so long as they are not actually indented by a sharp blow from any hard body they are as efficient and as enduring as wooden slides, they are very much cheaper. Moreover, they pack into a smaller space. Changing Boxes.— A changing box is an appliance for storing a number—generally a dozen—of plates, any one of which may be brought into position for exposure. These are ingenious contrivances, but it would be quite out of place to go into details of their construction here. They are not to be recommended for large sizes. I know that the maker of one of the best changing boxes made, although he does not absolutely refuse to make a larger size than 10 by 8, tries to dissuade his customers from giv ing orders for such. It might, indeed, perhaps be said that dark slides are to be preferred to changing boxes for all sizes over 8} by G}. BoU-Holders.—The difference between roll-holders of one kind and another is not, as in the case of dark slides, merely the difference between one type of apparatus and another. It is a case of the difference between the different patented inventions of different firms, and as, in such a case, it would be invidious to make comparisons, the roll-holder must here be dismissed with a word only. Indeed, the only thing I really want to point out here is that only a small fraction of the advantage of films is realised unless a roll-holder is used. The only objection to the roll-holder that I know of is, that it makes exposing so very easy that the user is liable to keep shooting away at all and sundry kinds of things without duo con sideration. Levels, ffc., for Securing Vertical Adjustment of the Camera Back.—When architectural work is done, it is essential that the back of the camera be vertical. A slight devia tion from the vertical will not give appreciable distortion so long as the angle included by the lens is not great, but if a wide angle be included, a very small deviation from the vertical will produce a most noticeable effect. For this reason, many modern cameras are fitted with some appliance for showing when the back is really ver tical. The commonest is a spirit level fixed on to the top of the back. When this top is horizontal, the ground glass is vertical. If there be but one level, it is fixed pointing “fore and aft,” as this direction—or, more strictly, in a plane at right-angles to it—is that in which verticality is of most importance, Any accidental tipping