Home Movies (1954)

Bow to use the Exposure Meter By LEONARD CLAIRMONT T N ORDER to get perfect results on the screen it is first of all necessary that the exposure be correct — and there is but one correct exposure for any given subject, no matter in what way we look at it. The correct exposure is that which will give the balance of highlight and shadows in the finished product which the cameraman originally intended to produce. If the effect he was striving for was attained by adhering to his calculations, then the resulting exposure should be considered the correct one. To some extent it may be said that correct exposure is a matter of preference, provided we stay within the boundaries of good photographic practice. Thus, the fact that the best exposure is usually something more than just the theoretical standard, we may well speak of it as an art. If a picture is to depict gaiety and frivolity, then the exteriors may be slightly over-exposed to match the mood of the high-key interiors. If low-key lighting sets the mood in a dramatic interior, then this should be matched with similar exterior scenes by a certain amount of under-exposure. A cameraman with a sense for the esthetic and knowing the limitations of his equipment will regulate his lens opening to create the most pleasing effect. But before we go artistic with our exposure, let's make sure we understand the full meaning of consistently good exposure technique, as the importance of scientific approach to perfect exposure cannot be over-estimated. In caluculating exposure, the following factors should be considered: 1. Lens aperture ( coated or uncoated lens) . 2. Shutter opening. 3. Camera speed. 4. Emulsion speed. Your exposure is all important to the laboratory and if consulted in advance can pull up an underexposed negative — but this won't work with color. Consult him before shooting. For head and shoulders shots get in close and take a few readings from various angles; average what you get, then shoot. 5. Intensity of light source. 6. Brightness range of the scene. Each of these six factors is basic photography, and therefore shouldn't need to be elaborated upon. There are several methods for computing exposure, but only one that is absolutely reliable — with the use of j photo-electric exposure meter. This type of meter, used by most cameramen the world over, consists of a light-sensitive cell which, when energized by light, forms an electric curlent. The amount of this current is proportionate to the intensity of the light received by the cell. The electncal current formed is measured on the graduated scale, and the exposure computed. Many exposure meters now on the market measure up to near perfection, but every cameraman usually prefers his own favorite make. Professionals all over are using such meters as General Electric, Weston, Norwood, De Jur. Electrophot, etc. Personally, I prefer the General Electric, Type W 68, using the A.S.A. exposure index. All meters of this type measure light in terms of foot-candles. When the light from one candle falls upon an object at a distance of one foot, the illumination on the object is said to be one "foot-candle". If we, for instance, have 25 candles (or a 25 candle-power lamp) at one foot distance, the illumination would, of course, be 25 foot-candles. If we change the distance, the illumination will vary inversely as the square of the distance, because the cone of light which covers one square at a foot will cover 4 squares of the same size at 2 feet. 9 squares at 3 feet, and so on; and since the same light falls on one square at one foot is spread over 4 squares at 2 feet distance, it is naturally Yi OI" tne strength ,so that a 25 candle-power lamp at one foot distance gives an illumination of 25 footcandles, and at 5 feet distance it gives only one foot-candle. This is the principle on which the photo-electric exposure meter is calibrated. The light falling on an object is known as the "incident light", and is measured in foot-candles. The light bouncing back from an object is the "reflected light", and is measured in "foot-lamberts". a foot-lambert being the brightness of a surface which reflects diffusely all the light which falls on it and on which the illumination is one foot-candle. So what system should be used in • See METER on Page 36 25