Nikon N4004s - Manual (Page 75)

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 ISO200 being twice as fast as
ISO100, and half the speed of ISO400 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.