International photographer (Jan-Dec 1941)

Under-exposure will cause: 1 . Loss of full scale of tone. 2. Loss of detail in shadows. 3. Too high a contrast in negative. 4. Too thin a negative for good print quality. 5. Blueish hue in color film. Correct exposure results in : 1. Film of finer grain. 2. Better definition in the highlights. 3. Better detail in the shadows. 4. Sharper definition. 5. Greater depth of focus. It is often said by many photographers, especially experienced men — "I don't need an exposure meter because I get good results without one." The human eye is an extremely poor light-measuring device at its best. Tests indicate that the eye cannot detect less than a 30% change in light. When reduced in terms of light, this represents a change in exposure of one-half an F stop. And on films with narrow ranges of latitude, this is quite a noticeable difference in the quality of the negatives. It is also extremely difficult for the eye to correlate the proper combination of modern high film speed, the F stop and shutter speed by looking at the light conditions. A bright, blue, clear day may be perfectly comfortable to your eye, and the exposure meter will show that intensity of light registers hundreds of candles per square foot brightness. Under other conditions, such as a hazy day, you may be squinting at scenery extremely brilliant but the exposure meter will indicate a lower brightness level of the object, and call for a longer exposure. Haze and appearance of the atmosphere causes this appearance brightness but it is not the kind of brilliance that affects the photographic emulsion. Also, in photoflood interior lighting, you seem to have an extremely brilliant illumination, yet when measured with an exposure meter, it shows but a few candles per square foot brightness, which is an extremely low level of illumination. Although the human eye has the ability to see from a mere fraction of a foot-candle, such as a moonlight night, to the brightest beach or snow conditions, it cannot be depended upon for the accurate measurement essential to good photographic results. It is helpful to know how an exposure meter is built, to obtain the best possible results from it. The G-E meter has been carefully designed to give the best results for all photographic light measurements. The photoelectric cell is made of an iron plate coated with selenium. The selenium is covered with a transparent layer of precious metal which allows light to go through to affect the selenium, which converts the light into electrical energy. The photoelectric cell is an extremely interesting generator, complex in manufacture, and how it works is a mystery to our best engineers. The perfection of the presentday photoelectric cell is a result of many years of development. It has a wider range of color sensitivity (see Fig. 4), is stable, and possesses an almost indefiinite life. Tests made in our laboratory since 1932 on cells indicate a very slight loss of efficiency. (Fig. 5) In our life light test, cells are placed under a laboratory skylight and are exposed to the full intensity of the sun every day of the year. If we figure rather liberally that normal use is about one hour per day, a years labor atory exposure represents a life of 24 years for the cell. The photoelectric cell is coated with transparent lacquer before it is sealed in its case. Current is taken off of the cell through silver contacts and flows into a standard electrical instrument. This consists of a large strong magnet, with a coil of thin wire placed in its magnetic field. (Continued on page 28) 2.8 2.6 ■ 2.4 2.2 k 0^ 2.0 ^ 1-8 IS '-6 \ 1.2 > <n z Ul o usable rof /?JTG/OA/ , \ i I i i LOG "1,0 J 8 .6 ■ —.4 2 ■ EXPOSURE 4 3 2 T i 0 1 2 3 4 5 SUBJ£CT _ 0/?/GHTN£SS Ftp. EL~ Motion Picture Equipment Studio and Laboratory Tested Since 1929 AUTOMATIC DEVELOPING MACHINE COMPLETE IN EVERY DETAIL Immediate Delivery HOLLYWOOD USERS CAN ATTEST MACHINE'S SUPERIORITY USERS ALL OVER THE WORLD CAN RECOMMEND THIS DEVELOPING MACHINE THIS PRACTICAL MACHINE CAN BE USED IN ANY CLIMATE EASILY INSTALLED— QUICK DELIVERIES © SENSITESTER — For Light Tests and Sensitometric Strips • SOUND RECORDING SYSTEMS ART REEVES 1515 Cahuenga Blvd. Cable address: ARTREEVES Hollywood, Ccdifornia. U. S. A. International Photographer for June, 1941 19