International photographer (Jan-Dec 1941)

UsioiQ Tht EXPOSURE METER (Concluded from June issue) Exposure can be determined by the measurement of light falling on the subject or light reflected from the subject. Either can be measured to obtain correct exposure. Obviously the amount of light falling on the subject determines the amount of light that will be reflected. Usually, it is more convenient to measure reflected light, but the meter has to be restricted to see the same scene as the camera. In the G-E meter, this requirement has been met mechanically, by means of a directional hood or baffle which limits the field of view to that of the average camera. It has a horizontal angle of about 50 degrees, and a vertical angle of about 30 degrees. The vertical angle is made purposely narrow to exclude bright sky and foreground which tends to cause error in exposure. As a rule, exterior scenes are made by measuring the scene in the same manner that the picture is taken, with the meter pointed at the scene. In interior work where extremely high contrast exists, a more correct reading can be obtained by measuring the light falling on the subject, rather than the reflected light. These incident-light readings are taken with the hood removed and the meter pointed at the camera from the subject. On a scene well illuminated by artificial light with a background of no particular interest, only the actual light on the subject is measured. If a reflection measurement were used it would be necessary to average several readings to obtain the best possible exposure for the over-all scene. So in most cases best results can be obtained by measuring the light falling on the subject of interest. The calculator on the G-E meter is simply a slide rule which enables you to convert light reading and film value into the proper combination of F stops and shutter speed. The proper combination of F stops and shutter speeds are lined up on the calculator and after it is adjusted for a reading any combination then visible will produce the correct exposure. Small lens openings line up with longer exposure time and large lens openings are opposite shorter exposure time, but in each case there is a definite quantity of light that must fall on the film. Other calculators can be supplied for the movie and sports photographers. In the case of the movie camera there is a certain fixed shutter speed, such as 16 frames per second. For the sports photographer who must use a fast shutter such as one onehundredth or one one-thousandth of a second to stop the action there is also a present calculator with shutter speed set with the film value. When the light is measured the light value indicates the By GLEN C. ANDERSON, General Electric Company proper combination of F stop to use with no further adjustment. Hoods with these different types of calculators are readily interchangeable on the G-E meter. Now that we know the characteristics of the sensitive emulsions that we are working with, the proper approach in determining the values of film speeds, and the characteristics and design of the instrument we are working with, we can intelligently use these instruments to their best advantage. Working outdoors, with flat, side, or back lighting, the meter need only be pointed at the subject to obtain a usable reading. You will notice that sidelight will usually call for about twice the exposure that a sunlit scene requires, because only half as much light is being reflected toward the camera. To photograph a subject without regard for background, take a meter reading right on the subject. If your subject is out of reach hold your hand in the same relative position and take a meter reading on the back of your hand. Extensive tests indicate that the color of the average person's hand is sufficiently neutral to be used satisfactorily for most subjects. If you are in bright sunlight and your subject is in the shade, the light intensity of your subject can be duplicated easily by throwing a shadow across your hand for the (Continued on page 26) G-E EXPOSURE METER, TYPE DW-48, WITH COVER CLOSED, SET FOR READING 4N BRIGHT LIGHT. 577B12 G-E EXPOSURE METER, TYPE DW-48, WITHOUT HOOD, READY FOR USE IN DIM LIGHT. INCIDENT-LIGHT METHOD BEING USED 18