Nikon Camera N90 - Manual (Page 230)

TTL auto flash
The camera’s light sensor measures flash illumination, as
reflected by the subject on the film and shuts off the flash when
measurement indicates correct exposure. Because the sensor
that controls the flash receives light through the lens, TTL auto
flash can be used for bounce flash photography, fill-flash,
multiple flash photography, etc. An additional advantage of TTL
auto flash is that you can use a wide range of aperture settings,
while ensuring correct exposure.
Wide-Area AF
Cross-shaped Wide-Area Sensor (7mm horizontal, 3mm
vertical) with no dead zone results in sharp focus for most
subjects, including those without vertical lines.
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