Pentax P3n P3n Manual - Page 43
Shutter/Aperture
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The shutter-speed and aperture combination in the Programmed AE mode is shown in the chart. The red line represents the variation of shutterspeed and aperture combination with an f/1.4 lens. Note that only the shutter-speed slows down after the lens aperture reaches its limit of f/1.4 in combination with a speed of approx. 1/30 sec. When you use a lens with a different maximum aperture, the exposure program varies the aperture and the shutter-speed in combination until reaching the maximum aperture of your lens. For example, with an f/2.8 lens the program varies the combination as shown by the red dotted line. Note that only the shutter speed changes after the maximum aperture is reached. The fine red line in the Programmed AE diagram indicates the Automatic Exposure control range fbr a lens with minimum aperture smaller than f/22, or for a film with ISO speed other than 100. . Metering Range and Shutter/Aperture Coupling Range The metering range means the range of subject luminance within which the built-in exposuremeter works to control exposure. The shutter/ aperture coupling range is that part of the metering range within which shutter-speed and aperture value can be combined for proper exposure control. When you use a 50mm f/1.4 normal lens and an ISO 100 film, the metering range is from EV 1 (f/1.4-1 sec.) to EV 18 (f/16 -1/1000 sec. or f/22-1/500 sec.). The range varies according to film speed (ISO). The variation of the metering range is shown by slanting lines which shift ISO ratings. The frame in the center shows the meter and shutter/aperture control coupling range. EV (Exposure Value) EV represents a combination of the shutterspeed and the lens aperture which is determined by the film speed (ISO) and the brightness of the subject. 41 •