International photographer (Jan-Dec 1934)

February, 1934 T h INTERNATIONAL PHOTOGRAPHER Seven J. B. Reade actually applied it to photographic experiments. The remarkable feature of this important agent, Hypo, is that all through the various stages of the development of photography Hypo has held a peculiar position, uninfluenced by, and independent of, the most modern developments. It is interesting to observe that in proportion to the volume of other elements in the process it is required in the greatest quantity of them all. But if its cost had remained at "half a crown an ounce," as at the time of Read's experiments, the cost of photography would be prohibitive. Fortunately, industrial chemistry and nature's bounty provide it today as one of the cheapest ingredients. The Wet Plate Despite the popularity of the Daguerreotype and the improved Talbot idea, students continued to experiment. La Gray suggested a glass support and collodion in which to suspend the silver salt. In 1848 F. Scott Archer, acting on La Gray's suggestions introduced the first real photo emulsion, i.e., the wet plate, so called because it was necessary to expose it wet, due to the salt crystalizing if allowed to dry. Despite this disadvantage the wet plate produced results excelled only in some of the most modern developments. The Dry Plate The wet plate restricted the process to well defined limits — individual skill in manipulation ; photographing only still objects and the limits of portability. Dr. R. L. Maddox found that gelatine entered into a peculiar combination with silver salt so as to allow the emulsion to dry without crystalization. This combination has been one of the most interesting features of the commercial development. The so-called cooking and ripening under varying temperatures greatly influences the speed of exposures. This together with the adoption of celluloid as a base, has made possible two great commercial departments, the amateur hobby and the motion pictures. The Panchromatic Emulsion In 1801 Johann Wilhelm Ritter demonstrated that violet rays were apparently the more active agents in photography. Subsequent experiments confirmed the opinion that photography, at its best, was a judicious balance between blue objects that showed too bright and red ones that "came out" too dark. The next step was to develop an emulsion that would render all the colors in their proper tonal values. Modern research has found the means for modifying the gelatine emulsion by the introduction of particular elements that increase the sensitivity over those troublesome portions of the spectrum, particularly the reds. The panchromatic emulsion has likewise made possible all the known color processes. Reversal Process The growing popularity of the 16mm. pictures has suggested the reversal process, or direct positive, designed to reduce the cost of amateur cinematography. It involves the use of certain chemicals that attacks the silver image but do not affect the unexposed compound. These chemicals suggest a final reference to hypo which acts only on the free silver, as before explained. These peculiar characteristics inspire the utmost reverence for nature's resources and the marvelous co-ordination of the elements in chemistry — all for the benefit of man's industry. In conclusion, let us summarize some of the salient points in the development of photography: (1) The Camera Obscura: anciently observed by Alhazen, Arabian philosopher in A. D. 1000; first applied by Baptista Parta; miniscus lens added by W. H. Wallaston in 1812. (2) Fixing the Image: by Niepce about 1825. (3) The Daguerreotype: first commercial photographic process. (4) Talbot Calotype: contemporary with Niepce and Daguerre, and the first negative and positive experiments. (5) Hypo: its properties noticed by Hershel and applied by J. B. Reade, in 1837. (6) Wet Plate: by F. Scott Archer, 1848 ; development of latent image with pyrogallic acid. (7) Dry Plate: gelatine emulsion introduced by Dr. R. L. Maddox ; snap shot exposures. (8) Adoption of Celluloid Base: Eastman Kodak Co. in 1889; roll films for amateurs and motion pictures. (9) Panchromatic Emulsion: rendering most of the colors in their proper tones ; first adopted for motion pictures about 1924(?) (10) Reversal Process: used in making autocrome plates and direct positions. Comparative Speed Niepce's asphaltum process 8 hours exposure Daguerreotype 1 hour exposure Talbot's Calotype 3 minutes exposure Collodion Wet Plate 10 seconds exposure Early Gelatine Emulsion 1/1 5th second exposure Modern Pan Emulsion l/55th second exposure Above under similar light conditions at stop f/16 HAIL THE NEW SUMMAR LENS HE long-promised Summar f :2 50 mm. lens in collapsible mount for Leica Cameras is now ready for delivery. This lens embodies several really astonishing characteristics, among which might be mentioned its superb color correction and absolute crisp-sharpness, even at its widest aperture. A perfectly flat and brilliant field is produced. The outstanding feature of the Summar lens is its sharpness at every diaphragm stop. It is therefore, an ideal all-purpose lens, besides being an excellent speed lens. Because it is based on an entirely new optical principle, it does not suffer from aberations which are usually associated with speed lenses, among which softness at large apertures is a disturbing factor. The new Summar in collapsible mount differs somewhat from the standard Elmar and Hektor 50 mm. lenses for the Leica. First, the depth of focus collar is seen from above the camera, making it easily read without turning the camera around. Second, the lens itself does not rotate as the lens is focused. A spiral focusing mount causes the lens proper to glide forward and backward without turning. Third, the diaphragm control ring is situated near the front of the lens with the figures facing upward so that they may be read from above as the camera is held in the hands. Fourth, the Summar collapses to within three-quarters of an inch from the front of the camera, making it possible to carry the camera in the pocket or carrying case without the inconvenience of a rigidly projecting lens. Those who have already secured the Summar are actually loud in their praises of it. It is hailed as the finest lens of its kind and type, and all tests made so far bear this out. The Summar F:2, 50 mm. lens may be obtained in both rigid and collapsible mounting. For further details, write to E. Leitz, Inc., 60 East 10th Street, New York City. YOU'LL HAVE TO HURRY! Order Now. The Cinematographer's Book of Tables Will Be Ready in April. Please mention The International Photographer when corresponding with advertisers.