Olympus OM-2 - Page 57

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-TTL Centralized Control Flash
by T20/0M-2 Combination
The T20 utilizes the OM-2's own
built-in SBe light sensors. The
;ensors read the build-up of light
' rom the T20 which passes through
he taking lens to reach the film
; urface, letting the electronic
orain of the camera cut off the
flash em ission when the correct
exposu re has been made.
On
conventional auto flash units,
the auto sensor is bu ilt into the
flash unit. The sensor regulates
flash emission
independently of
the camera. While normal auto flash units can also give a
correct exposure, they are far less vel'Satile and convenient
in use. The ir drawbacks include:
CD The need to set film speed and lens aperture on both the
camera and the flash unit , which leads to exposure errors
caused by mistaken film speed and/or aperture alignment.
... With the T20/0M-2 combination, once these values have
been set
on the camera there is no need to reset them on
the flash unit.
® Restrictions on the f-number that can be used . ... With
the T20 / 0M - 2, f-number can be selected freely because the
56
light is measured through the camera lens.
® Inability to change the light measuring angle of the sen-
sor according to the taking angle of the chosen lens .... With
the T20 / 0M - 2, l ight measuring angle always coincides with
the p icture angle of the taking lens.
® Restricted close- up range and incompatibility with ex-
tension tubes, etc .... With the T20 / 0M -2 , close- up and
diffused flash photography can be made easily. As the ex -
posure
is calculated inside the camera, the method of using
the flash unit are entirely unrestricted .