Ttl Flash - Olympus E-3 User Manual

Guide number of flash
Aperture set on lens
As an example, if you were using the FL 36R flash which has a
guide number of 36 in meters at ISO 100, and you wanted to
shoot with an aperture of f=11, your maximum shooting distance
would be: 36/11=3.2 meters.
The same calculation on the FL 50R would yield the following
result: 50 (Guide number in m at ISO100)/11=4.54 meters
The built-in unit of the E-3 has a guide number of 13, thus at
f=11 you would have an operating range of 1.2 m (approx). The
above results, however, are the theoretical limits when there is
no other lighting present.
POWER USER TIP: If you set the camera to use AUTO ISO when
using a TTL flash unit (or the built-in unit) the camera will automatically
adjust the ISO to compensate for out of range images. This, in effect,
multiplies the effective guide number of the flash unit in use to increase
the practical working range and avoids slight under-exposure if working
at the or near the theoretical maximum of the TTL flash unit in use.

TTL FLASH

Luckily, the E-series cameras incorporate the famous TTL
Through The Lens/Off the Film/Image Sensor
( ) flash exposure
system pioneered by Olympus. This adds considerably to the
available theoretical range when shooting with additional ambient
light sources.
The camera incorporates a sensor in the base of the mirror box.
This measures the illumination being reflected from the subject
during the actual exposure. The central computer then cuts-off
the illumination of the flash unit once the main motif has been
correctly exposed.
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