Nikon FG Instruction Manual page 21

much light as 1/60 sec.
Note: When you set the shutter speed/mode selector dial to
either M90 or B, the exposure meter does not work and the
viewfinder LEOs don't light.
M90 (1/90 sec.)
At this setting, the shutter operates mechanically at
1/90 sec., and is used mainly when the battery is
drained and other shutter speed modes are not
operable, and for flash photography with an elec-
tronic flash.
B (Bulb)
At this mechanical setting, the shutter curtains '$J
remain open as long as you press the shutter release
button. B is used for long time exposures.
Note: When the shutter speed/mode selector dial is set
somewhere between 1 sec. and M90 and the shutter release
button (f!, is accidentally depressed, the shutter curtains re-
main open. If the film is rewound in this situation, every frame
will be re-exposed, damaging the pictures taken. Therefore,
before rewinding make sure that the selector dial is not in this
intermediate position.
The Nikon
FG
employs
TTL
(through-the-Iens) center-
weighted full-aperture exposure measurement which
measures the amount of light passing through the
lens with the aperture fully open, thus always assur-
ing a bright finder image during shooting. Exposure
measurement emphasis is placed especially on the
brightness in the 12 mm dia. central area (refer to
page 15), although the meter reads the light over the
entire focusing screen. Thus, correct exposure is
assured when shooting with the main subject situated
in this central area.
On both P and A modes, the
FG
employs instan-
taneous stopped-down exposure measurement. This
measurement system sets the optimum combination
of shutter speed and aperture at the actual split-
second moment of picture taking, assuring accurate
exposures even if the light changes at the very last
instant. A sensitive SPD (silicon photodiode) is used
to measure light intensity.
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