Pentax SF1 - Page 43

Programmed AE Diagram
This camera has three Programmed AE modes — Normal
Program, Program Action and Program Depth. The thick
solid lines of the diagram at left represent the shift in
the combination of shutter speeds and apertures. This
combination can be shifted up to the maximum aperture
of the lens in use: the combination of an f/2.8 lens is
indicated by a red dotted line as an example.
In the Normal Program mode, the combination is
automatically shifted to a program for one of three
sub-modes — Wide, Standard and Tele — depending on
the lens in use.
The Program Action mode is programmed to select a high
shutter speed.
The Program Depth mode is programmed to increase
the depth of field by selecting a small aperture.
The thin solid lines and thin dotted lines on both sides
of the diagram indicate different coupling ranges when
lenses with different maximum and minimum apertures
are used, or when the ISO film speed is changed. As
the aperture range of the lens (f/1.4 — f/22) changes,
the limits of the metering range change as well.
Metering Range and Shutter-Speed/Aperture Coupling
Range
Metering range refers to the range of subject illumination
within which the built-in exposure meter can operate to
control an exposure. The shutter-speed/aperture coupling
range is a part of the metering range within which possible
combinations of shutter-speed and aperture values for
proper exposure control can be found. For example,
the metering range for a 50mm f/1.4 standard lens with
ISO 100 film is from EV 1 (f/1.4, 1 sec.) to EV 20 (f/22,
1/2000 sec.).
As the ISO film speed changes, the metering range
changes as well. The thin slanted red lines in the diagram
at left indicate the change in metering ranges in relation
to ISO film speed. The inside of the center frame
represents the meter and shutter-speed/aperture coupling
range.
EV {Exposure Value)
EV represents the brightness of the subject and is
indicated by a number.
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