Nikon N4004s Instruction Manual page 55

Guide numbers:
The number given to a flashbulb or electronic
speedlight unit to indicate its power. A guide number may be
quoted in meters or feet, and depends on the speed of the film
being used . Quoted guide numbers assume a relatively efficient
reflector surrounding the flash source, in an average -sized room.
ISO:
The international standard for representing film sensitivity
(speed with which it reacts to light). The ISO film speed scale is
arithmetical, with a film speed of IS0200 being twice as fast as
IS0100, and half the speed of IS0400 film.
LED: Abbreviation of Light-Emitting Diode. Used to provide
indications inside the camera viewfinder.
Multi-sensor metering: Nikon 's exclusive metering system .
Drawing on its rich experience of auto exposure technology,
Nikon has incorporated a unique multi-sensor light meter into
the N4004s. The multi sensor provides additional information
to Decision Master System by dividing the scene into three
areas to instantly and automatically gauge brightness and
contrast. This enables the N4004s to handle all kinds of
lighting situations , including high-contrast or backlit scenes,
or scenes with a bright sun in the picture.
TTL:
Abbreviation of Through-The-Lens. Most SLR cameras
have built-in meters which measure light after it has passed
through the lens, a feature that enables exposure readings to
be taken from the actual image about to be recorded on film,
whatever the lens' angle of view and regardless of whether
a filter is used.
TTL auto flash mode: In this mode, the camera 's light sensor
measures flash light, as reflected by the subject on the film, and
shuts off the flash when measurement indicates correct expo-
sure. Because the sensor that controls the flash receives light
through the lens, this mode can be used for bounce photography,
fill-in flash, multiple flash photography, etc. The major advantage
of this mode is that you can use a wide range of aperture
settings that will give correct exposure.
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