Electronic Flash in Digital and Film Photography 337
In manual fl ash, lens apertures must be manually matched to the fl ash distance and must
be changed when the fl ash is moved closer or farther away. This approach is time-consuming
and should be considered only in special situations.
In automatic fl ash, a sensor built into the fl ash unit measures the light refl ected off the
subject and then determines the fl ash duration that provides correct exposure and turns off
the fl ash at the proper time. Automatic fl ash eliminates the need for matching aperture to
fl ash distance. You only need to set the aperture value on the unit and you can then move
closer or farther away without any additional adjustments. Automatic fl ash is a good choice
when a dedicated fl ash system is not available. Dedicated fl ash should, however, be the choice
for all location fl ash photography indoors and out with Hasselblad camera models that offer
dedicated fl ash.
DEDICATED FLASH
In dedicated fl ash, the fl ash exposure (the fl ash duration) is determined by a sensor built into
the camera, which measures the light refl ected off the image plane (OTF). This can be the
fi lm surface or the surface of the digital imaging sensor. The fl ash sensor in 503 and other V
system and in H system cameras measures the light refl ected off a 40 mm center area of the
image plane. Visualize the measured area when composing the image on the focusing screen
to ascertain that the main subject that must have the proper fl ash exposure is within that
40 mm center area.
For dedicated operation, fl ash unit and camera must be electronically interfaced requiring
fl ash units or adapters that are made for a specifi c camera system.
The Advantages of Dedicated Flash
Dedicated fl ash can provide better exposures and allow faster shooting while eliminating mis-
takes for the following reasons:
● The sensor measures the light that actually reaches the image plane in the camera.
● The metering is based on the selected lens aperture, and you can change the aperture without
making any other adjustments.
● With the light measured through the lens (TTL),the measured area is matched to the focal length
of the lens.
● With any lens on the camera, you can visualize the area measured by the fl ash sensor when you
compose the image on the focusing screen.
● The metering works with direct or bounced fl ash, whether the fl ash is on or off the camera.
● You need not compensate when using fi lters, teleconverters, or extension tubes.
● The ready light may be visible in the viewfi nder, so you know when you can take a second pic-
ture without removing your eye from the fi nder.
● An exposure signal may show after the picture whether the image area received a suffi cient
amount of light for correct exposure.
● The brightness of the fl ash can be adjusted to create any desired lighting ratio between the fl ash
and existing light.
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