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BASIC OPERATION
F Setting the Aperture Ring and the
CAT Switch
The amount of light that is allowed to strike the film is determined by the lens diaphragm. This amount of light is represented by "f" numbers or f/stops engraved on the aperture ring which clicks into place as it is rotated. The f/stop designations indicate the opening formed by the diaphragm, and this opening is called the aperture. On the standard 50mm lens, the engraved f/stops are 1.4, 2, 2.8, 4, 5.6, 8, 11, and 16. At f/1.4, the lens is at its maximum aperture with the diaphragm wide open. For this reason, f/1.4 is said to be a large f/stop even though it is small in numerical value. And con- versely, f/16 is the minimum aperture of the lens and is a small f/stop. The relationship between successive f/stops is arithmetic: as you close down the dia- phragm, each f/stop indicates half as much light as the proceeding one. When operating the aperture ring manually, you may use any aperture setting. For normal AE operation, the aperture ring must be set at the green mark. Hold in the AE lock pin while turning the aperture ring from f/16 (or f/22 on some lenses) to the 'A' mark. At this special setting, the aperture ring is disengaged, allowing the camera to adjust the lens diaphragm automatically to any f/stop setting. Also, to make sure that the camera selects the proper f/stop, the CAT switch must be set
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