International projectionist (Jan-Dec 1947)

Eye Views Photo Graininess Through 'Fingertip' Touch THE human eye detects graininess in photographic enlargements of small negatives in much the same way that a fingertip feels the roughness of a textured fabric. This comparison, based on existing physiological information about the motion of the eye, was made by Drs. Lloyd A. Jones and George C. Higgins in reporting their investigation of photographic graininess in Kodak Research Laboratories. The two scientists said they now believe that the appearance or nonappearance of graininess in a photograph is based pri marily upon movement of the image over the eye's sensitive retinal receptors. This movement takes place during the eye's "fixation pauses" lasting no more than two or three seconds. The Kodak researchers explained that it is well known that in examining an object the eye looks first at one area and then another. During the brief pauses when the different areas are examined, the eye appears motionless. Actually, however, as other researchers have found, during these pauses the eye vibrates rapidly. The central fovea, where vision is sharpest, flicks rapidly over small fields of the object being viewed. This effect of the eye's vibration during such a "fixation pause," it was pointed out, ,0,..r ««• "r s"vl i discriminating exhibitors everywhere are installing THE NEW "AA" PROJECTOR AND MOTIOGRAPH, LIFELIKE SOUND • Write for literature or see your Indepen \ dent Theatre Supply Dealer for a free demonstration. MOTIOGRAPH, INC. 4431 W. LAKE ST., CHICAGO 24, ILL. Producing the Setter Projectors for Over 50 Years. EXPORT DEPARTMENT; Frazar & Hansen} Ltd. 301 Clay Street, San Francisco 11, California Water electric (positive carbon cooler) for mirror arcs. The answer to more light and whiter light and less heat at the film. (Note all of the features listed below.) 1. Gives a full crater filling the mirror with more light. 2. Eliminates carbon penciling. 3. Carbon heats only one-half inch behind crater. 4. Resistance remains constant regardless of length of trim. 5. Positive carbon constantly in line. 6. Gives more and wider light. 7. Greater coverage of the aperture. Write us today for full information on the answer to your light problems. HUFF'S MANUFACTURING CO., 659 W. Jefferson Blvd., Los Angeles 7, Calif. is much like a finger which feels little while resting on rough cloth but senses texture when moved over the surface. These vibratory movements of the eye subject the retinal nerves to light of varying intensity or an "illuminance change or gradient." "Gradient sensitivity" is the term which the Kodak researchers have coined for the ability of the eye to detect these "illuminance changes." Part of the Kodak research technique involves the use of observers who examine magnified images of developed photographic deposits to determine what constitutes "just perceptible" graininess. From their investigations the two scientists now believe that a relatively small group of the eye's retinal receptors — some 1500 cones clustered around the center of the fovea — largely determine the final judgment of visibility or invisibility of graininess. Beyond this central field of the eye, they point out, the ability to see detail falls off rapidly, decreasing by as much as 10 per cent even, at the outer edge of a very small central field. Requisites of Visual System Through their research and through application of existing knowledge of the human eye, they hope to obtain a correlation between granularity, or the physical properties of the photographic image, and graininess as seen by the eye. Both Jones and Higgins feel that if granularity measurements are to be of value in predicting graininess, they must be made in a manner consistent with the known methods of functioning of the human visual system. A method of measuring granularity which will correlate closely with the physiological quantity, or graininess, would be valuable to photographic emulsion makers interested in producing less grainy emulsions without sacrificing film speed. Dickinson of MPA, Passes Director of the MPA Conservation Department for 20 years, Arthur S. Dickinson died recently at the age of 59, after a long illness, in Santa Monica, Calif. Mr. Dickinson had retired last July from the Association, ending a film career that began in 1921. He joined the MPDA, forerunner of MPA in 1927 in a technical capacity, handling contact with the Society of Motion Picture Engineers, National Film Carriers, Inc., and the National Fire Protection Association. Born in Chattanooga, Tenn., Mr. Dickinson studied engineering at Georgia Tech and was a member of the Picture Pioneers, the NFPA, former financial vice president of the SMPE and a member of its board of governors. He is survived by his wife, the former Blanche Lynch, and two daughters. Order Your Copy of Projectionists' $3oo SERVICE MANUAL 34 INTERNATIONAL PROJECTIONIST • November 1947