Pentax P5 - Page 59

Programmed-AE diagram
The chart at left illustrates the combination of
shutter speeds and apertures inthe Programmed AE
mode. The thick lines represent how the combination
varies when the 50mm f/1.4 lens and ISO 100 film
are used.
As the "Pa" line indicates, the Program Action mode
is programmed to provide faster shutter speeds,
while the Program Depth mode, as the "Pd" line
indicates, is programmed to make the depth of field
greater. When using the lens with a different
maximum aperture, the combination of shutter
speed and aperture changes until the aperture
reaches its maximum.
When an f/2.8 lens is used, the shutter-speed/aperture
combination varies as indicated by the red-dotted
line.
The thin red-dotted line shows how the combination
changes when the lens with different maximum and
minimum apertures is used, or when the film speed
(ISO) is changed. As the aperture range (f/1.4-f/22)
changes, the limit of the metering range changes.
Metering Range and Shutter/Aperture
Coupling Range
The metering range means the range of subject
luminance within which the built-in exposure-
meter 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 shutter-speed
and the lens aperture which is determined by the
film speed (ISO) and the brightness of the subject.
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