The photographic news

• Bandzählung: 29.1885
• Erscheinungsdatum: 1885
• 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-id1780948042-188500006
• PURL: http://digital.slub-dresden.de/id1780948042-18850000
• OAI: oai:de:slub-dresden:db:id-1780948042-18850000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Seite I-II fehlen in der Vorlage. Paginierfehler: Seite 160 als Seite 144 gezählt.
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

428 THE PHOTOGRAPHIC NEWS. [Jvty 3, 1885. should not be heated many degrees above the temperature at which it sets. Ou the other hand, it is also difficult to coat paper with any gelatinous substance when it is too near the setting point, as might have been observed in any attempt to coat glass plates with a bromide emulsion when the liquid has become nearly cold. The speed with which a roll or band is made to traverse the surface of the emulsion has also much to do with suc cess. Both the temperature and density of the gelatine help to determine the speed ; but beyond these facts, prac tice alone can guide in formulating rules for accurate work. (To be Continued.') THE PHOTOGRAPHIC SOCIETY OF PHILADELPHIA. The proposed exhibition will be held during the Fall or Winter of 1885-86. Amateur and professional photographers are invited to send specimens of their best work for competition. The recent rapid progress in artistic photography, and the growing interest in the subject, lead the Society to hope that a collection of photographic pictures may be brought together which will be vorthy the critical attention of friends and the public. A diploma will be awarded, by a Board of Judges, for the best picture in each class. Every precaution will be taken that the conditions of classification are complied with. The place of holding the Exhibition, and the date, will be announced in a future circular. It is proposed that the Exhibition shall remain open to the public about one week. To facilitate the hanging of pictures by classes, it is requested that, as far as possible, pictures of different classes be not included in one frame. Intending exhibitors are requested to advise the Secre tary as early as possible, so that entry blanks, labels, &c., may be sent them in good time. Early notice in regard to trans parencies and lantern slides is particularly desired, in order that proper arrangements for showing them may be made. For all further information, entry blanks, labels, &c., applications should be made to the Secretary, Mr. Roberts. Redfield, 1601, Callow- hill Street, Philadelphia, Penn’a, U. S. America. Huies.—1. Both amateur and professional photographers may compete in all classes, unless otherwise specified. 2. No photo graphs will be received on single mounts less than 5 by 8 inches (except stereoscopic). All smaller than this size must be grouped on a larger mount for convenience in hanging. No unmounted prints will be received except from foreign exhibitors. 3. The same picture may be entered in more than one class, but can only be awarded one diploma. No diploma will be awarded in any class in which the pictures are of insufficient merit, as decided by the judges. The committee reserve the right to re ject all or - portions of any exhibit offered. 4. All entries must be made on blanks, which will be furnished on application, and which must be filed with the Committee at least five days in advance of the Exhibition, giving (when possible) the following information:—Number of pictures—Size of frame or mount— Classification—Subject—Lens—Plate—If for sale, Price—Ex hibitor—Address - Society. Ten per cent, commission will be retained by the Society for any pictures scld during the Exhi bition. 5. Each print must have a label attached by the ex hibitor, so as to be read from the front, stating class, subject, lens, plate, exhibitor. Blank labels will be furnished on appli cation. 6. All expenses for transportation to the Exhibition must be prepaid by the exhibitors. Return charges will be collected by carriers. 7. No pictures will be received later than five days prior to the opening of the Exhibition. 8. No pictures shall be withdrawn before the close of the Exhibition. 9. The Society will not be responsible for any loss or damage that may occur to any exhibit, but will use all reasonable care to prevent such occurrence. 10. Advertising in any form, in connection with any exhibit, is strictly prohibited. Classijication.—(1) Landscapes, any size—by professionals only, (2) ditto, over 5 by 8 inches, (3) 44 by 64 to 5 by 8 inches inclusive, (4) ditto, under 44 by 6} inches—by amateurs only ; (5) marine views, surf, (6) ditto, sail— by professionals only, (7) marine views, surf, (8) ditto, sail—by amateurs only-, (9) figure compositions, over 5 by 8 inches, (10) ditto, 44 by 6±, to 5 by 8 inches inclusive, (11) ditto, under 44 by 64 inches—by amateurs only ; “ Figure Compositions ” are to include groups, and all pictures in which one or more figures make the principal interest of the picture, and which are not included in the. “ Special Composition,” Classes No 15, 16, 17, and 18. (12) landscapes, (13) marine views, (14) figure compositions—by ladies only ; (15) cottage door, (16) wayside fountain, (17) village smithv, (18) ploughing—special compositions ; (19) animals, (20) still life, (21) flowers, fruit, &c., (22) trees, (23) snow and ice, (21) architecture, (25) interiors, (26) sculpture, (27) machinery and other manufactured objects, (28) microphotographs, (29) en largements, (30) instantantaueous effects, not otherwise classified, (31) platinum prints, (32) gelatino-bromide or chloride prints, (33) porcelain pictures, (31) transparencies, (35) sets of six lantern slides—negatives and slides to be made by exhibitor, (36) sets of six to twelve pictures, taken in a foreign country, or by a foreign exhibitor, (37) pictures by any new process not be fore publicly exhibited. Foreign exhibitors will please send their pictures by mail, un mounted, directed to:—The Photographic Society of Phila delphia, care Robert S. Redfield, Secretary, 1601, Callowhill Street, Philadelphia, Pa., U.S A. Suitable arrangements for properly exhibiting them will be made by the Society. They should be accompanied by a statement of value (for custom house purposes). As the time for holding the exhibition cannot yet be fixed, it is requested that pictures from abroad be sent to arrive during October, in order that they may be received in ample time for any date that may be decided upon. Immediate notice is desired from those proposing to send pictures. Uorrespondence. SUSPENDING THE ACCOMMODATION OF THE EYE. Sir,—In answer to Mr. A. Brothers’ letter in your issue of June 26th, I have pleasure in suggesting the following explanation of the fact referred to by him. When the gas jet is looked at steadily for a few seconds, it excites a certain definite area of the retina, and is seen under a certain definite angle of vision. This part of the retina becomes exhausted, and therefore, when the eye is directed to a dark screen placed exactly at the same dis tance from the eye as the gas flame was, a black space occurs in the field of vision of exactly the same size and shape as the flame. T he impression formed on the retina by the light of the gas flame is of a certain size and shape in direct proportion to the size and shape of the flame, and the parts of the retina corresponding to this certain shape becomes ex hausted ; hence a certain definite part of the field of vision is in darkness. The shape of this blind space is exactly correspondent to the shape of the light space in the visual field when the flame was being looked at; but its size vaiies, becoming smaller and smaller as it approaches the eye. . j When the eye looks at the gas flame, the rays of light pass from the flame to the eye in con verging straight lilies, forming a cone of light rays, the base of which is the flame of the gas, and the apex at the nodal point of the eye, which is just posterior to the lens of the eye ; the outer lines of this cone measure what is called the visual angle, under which the flame is being viewed. The cone is a cone of light rays, and it is in the exact position of this light cone that the dark cone or dark space referred to above occurs. In other words, the light cone is the part of the field of vision corresponding to the part of the retina which is excited by the light from the flame, and which, when the eye is turned away from the source of light, becomes the dark cone. The shape of the base of this cone corresponds to the shape of the flame, aud if the screen be placed nearer to the eye than the flame, the shape of the base of the cone remains the same, but the size of the base becomes smaller ; hence the impression conveyed to the mind is, that the dark image of thegas flame is smaller, and vice versa. When the screen is removed from the eye further than the gas flame,