The photographic news

• Bandzählung: 6.1862
• Erscheinungsdatum: 1862
• 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-id1780948042-186200003
• PURL: http://digital.slub-dresden.de/id1780948042-18620000
• OAI: oai:de:slub-dresden:db:id-1780948042-18620000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Seite 1-72 fehlen in der Vorlage. Vorlagebedingter Textverlust.
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

572 THE PHOTOGRAPHIC NEWS. [November 28,1862. appears only of half its natural size, a phenomenon attribut able to a short retention of the impression on the retina after its formation and its cessation ; for, by suddenly rectifying the eyes to ordinary combined vision, the single image will at once be recognized of its natural size. Bight. Left. Let AB and CD represent the pictures of an arrow, as seen by each eye at a given distance, and EF and GH the pictures of the same object at a nearer distance. Let the photograph taken by the lens on the right side be mounted on the left side, and vice versa as in the adjoining figure. Let L and R represent respectively the left and the right eye. Draw lines from the right eye to the top and bottom of each arrow in the photograph marked “ right,” also from the left eye to the photograph marked " left,” At the points of intersection draw the arrows MN and OP ; these arrows will represent respectively the positions of the pictures of the original ob jects projected in space, with all the distances and sizes in true proportion ; but these arrows might represent parts of one and the same solid object, so that the points of inter section would depict the corresponding points of a solid picture. The arrows, of which AB and EF, etc., are supposed to be photographs, are supposed to be placed perpendicular to the plane of the observer, or to the surface of the paper, and to be twice as high as the elevation of the eyes above the horizon. The pictures are mounted so, or so deposited in the figure, that the distances BD and AC are respectively equal to the distance LR, or the distance between the centres of the eyes. For this reason BO will be equal to OR, as also DO to OL. In like manner AP and PR, and CP and CL, are equal to each other: and since the arrows are supposed to be perpen dicular to the paper, and the eyes above the plane of the paper at a distance equal to half AB, the distances AP and CP will be equal to BO and GO ; therefore, the superimposed pictures at PO will be equal to half AB or CD. The arrow, of which AB and CD are the pictures, is supposed to be placed at a great distance off, so great indeed that, in the strabonic stereograph, the distance from A to C will be equal to the distance between the eyes ; but the distance between all nearer- objects, as from E to G will be greater; therefore, the intersections of the two lines ER and GL, as also of FR and DL, will take place nearer to the eyes than P or 0, and in such a manner that EN or GN is less than NR or NL, as also FM or HM is less than MR or ML. From these circumstances we deduce the following con clusions : the superimposed pictures at MN are less than half the size of EF or CH inversely, as EN FM (which are supposed equal, since the arrow is intended to be perpendi cular to the plane of the paper) is greater than NR or MR (likewise equal). Secondly, the picture MN will always be greater than PO, because the angle ERF will always bo greater than the angle ARB, as long as EF is nearer to the eyes than AB It is evident too, in the third place, from the similarity of triangles, that the same proportion exists between the two superimposed pictures MN and OP, as between either pair of photographs EF and AB on one side, or GH and CD on the other. As I have already remarked, the two new pictures MN and OP thus formed by superimposition, will be very brilliant; in the first place, because they are condensed, on an average, to one half the size ; and secondly, because the light of either photograph is superadded. In addition to the superimposed picture, we have other two pictures much less brilliant, and at the same time indistinct, one on the right and the other on the left; that is, EF and AB are seen independently by the left eye to the left of the brilliant picture, whilst GH and CD are seen by the right eye independently to the right of the new solid picture. These secondary pictures I have not introduced in the diagram, because the lines would merely confuse the more important demonstration of the solid pictures. Their posi tion is found between the lines drawn from R to C and D, and from R to G and II on the right side; and then from L to A and B, and from L to E and F, on the left side ; and their size too, by some peculiar physical sympathy, is about half that of the originals, or in the same proportion as OP to NM, and probably respectively equal to them. Application of the Strabonic Property. — Whenever the practical photographer, or amateur, has taken a favourite stereograph, he is desirous right away of seeing a proof-sheet of his workmanship in the stereoscope, or of having a print taken of his negative, in order to test his success. On a tour it is not always convenient to carry a stereoscope to gratify his ardent desire; but it is not at all difficult to practise the strabonic exploit; and when this is once attained, you can examine your negatives the moment they are fixed. It is not only a great pleasure to be able to do this, but it is a saving of time. Again, with this property made quite easy and familiar, your right and left printed stereographs may be promiscuously mixed together without any subsequent embarrassment; for picking up two photographs of the same view, and placing them on any flat surface, as on a book, in juxtaposition, you can easily and instantaneously say which belongs to the right side and which to the left, or whether they both belong to one and the same side. Besides this, I have no 'doubt that before long we shall have strabonic stereographs on sale as numerous as the ordinary ones ; for each person's eyes will be his stereoscope. I do not know a greater treat in photography than that of taking up two card pictures, taken in the open air with a natural background, and with the binocular camera and to be able to produce the stereoscopic superimposition. Each blade of glass, each flower, the old hollow tree, the irregular rocks, the log-house, and the lake, are all presented in miniature solidity with the beloved friend in the midst in living nature. What a difference between such card-pictures and those flat silly things that are daily presented to us, whose background is almost universally a broken pillar or a baptismal font! Strabonic card pictures once introduced, and their beauties once descried, would soon drive away all those stiff photographic contortions and snobbish grimaces depicted in front of columns and regal staircases to the land of Proserpine. Injury to the Eye-sight by the Strabonic Manoeuvre.—Hints are frequently expressed, both by the laity and the medical profession, that such attempts as recommended in the present article, will be likely to produce permanent injury to the eyes, by producing internal strabismus. Such medical men do not investigate the grounds from which they derive their opinion ; they take it for granted, I suppose, that since to be able to see strabonically requires at the beginning an effort, therefore it is unnatural, and must of course produce an un natural result. Before such a conclusion can be established, we must first ascertain whether those persons who have ob tained the faculty of thus regarding the stereograph, have had their sight deteriorated, the axes of their eyes changed, or, in fact, have suffered any inconvenience whatever. For my own part I must and can with a good conscience (and 1