American cinematographer (Jan-Dec 1941)

The Norwood "Director" meter. Note hemisphere light-pickup, scale reading directly in f-stops, and manner in which photocell can be rotated to any angle. On opposite page, Karl Freund, A.S.C., is shown taking a reading with the Norwood meter preparatory to filming a scene for "The Chocolate Soldier." Note how meter's pickup duplicates lighting on Nelson Eddy's face. strument which will measure with accuracy the light actually affecting the photographic rendition of the key factor in his scene — usually the face of the principal player. From this he can balance the rest of his lighting visually to produce the desired artistic result, creating shadows and highlights as may be desirable. But to do this, it is necessary that the meter "see" the lighting on the subject as the camera does. If it "sees" the light without relation to the camera, its reading, while it may be technically accurate, will prove inaccurate photographically. This can easily be proved by taking two incident-light readings with a conventional meter on a subject, altering the angle but not the intensity of the key-light between the readings. To cite an extreme example, a reading of this type may be taken with the key-light placed close to the camera, producing a front-lighted effect. The second reading may be taken in a crosslight, with the light-source at the same measured distance from the subject, but with the lamp moved through a 90degree arc so that it now produces a cross lighting. Conventional key light measurements of these two set-ups would give identical readings. But practical photographers have for many years known it was necessary to double exposure— increasing it a full /'-stop — for cross-lighting. For this reason, Norwood has given his new meter a three-dimensional lightgathering surface, in the form of a hemisphere of ground celluloid placed over the meter's photocell "eye." When this hemisphere is placed in subject position and pointed directly at the camera's lens, the light falling on its three-dimensional surface reproduces exactly the lighting angles and relative intensities falling on the subject's face to affect exposure. In a flat front-light, it gives a high reading; in a cross-lighting of equal individual intensity, only half the hemisphere's surface is illuminated, while half is in shadow. Therefore the meter gives a proportionately lower reading, indicating approximately one /-stop more exposure is needed. If filler-light is used on the shadow-side, this, too, is registered by the meter, and the propoi~tionate exposure indicated. This principle has been engineered by Norwood and Freund into a compact and practical meter known as the Norwood "Director" Meter, which is the first product to be produced by a newlyestablished organization for cinetechnical research, the Photo Research Corporation. The heart of the instrument is a standard Weston photronic cell to which a standard Weston microammeter is permanently connected. Over the photocell is the ground-celluloid hemisphere which gives the meter its threedimensional pick-up. The photocell-housing is mounted rotatably on the case for convenience in operation, so that the light pick-up can be swung through a 180-degree arc to right or left with reference to the case and indicating dial, permitting readings to be made with assurance that the operator's body is not shadowing any photographically effective light from the photocell. The indicating dial reads directly in /-stops at the standard studio cine-camera exposure-speed of l/50th second. Compensation for different film-speeds is made by means of perforated metal masks which are slid into place directly over the photocell. These are precisionmatched to the individual meter, and are calibrated in terms of the familiar Weston film-speed ratings. These masks are further matched to coordinate with the individual processing conditions of the studio or film-laboratory where the user's film is to be processed. For the present, at least, these meters are to be sold only to professional cinematographers. And this makes practical a unique policy. The purchaser of each meter is given an opportunity to use his instrument in making practical photographic tests, under actual studio conditions. A test stage is provided by the firm, complete with sets, camera equipment, and the latest Mole-Richardson lighting units. The purchaser of the meter is required to make tests, using these facilities and with his test-film developed to the same standards as those employed by the studio or laboratory handling his regular work, until he not 2' \S Light-tests of both ends of an effect-lighted dollyshot, exposed with the new meter. Note uniformity of exposure throughout, and that even though an effect-lighting, the scene will print far down on the scale. only is familiar with using his meter, but has gained absolute confidence in it. "This," says Freund, "is a most important factor in using the Norwood 'Director' Meter. He has made it, I am confident, the most accurate and dependable meter ever built for professional use. But unless the man who uses it has sufficient confidence to rely on it absolutely, it would be much better that he did not use it at all. "Let me illustrate this. After I tain Norwood had worked out the fust experimental models of this meter, we subjected them not only to the most searching laboratory tests, but to practical photographic tests of every description, using all types of film, including (Continued on Page 440) American Cinematographer September. 194] 417