Canon 550EX User Manual
Page 66
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• Setting the Flash Ratio for Three Slave Units:
A, B and C
With three wireless slave units, slave unit A is the main flash, slave unit B is
the fill flash, and slave unit C is a supplemental flash. Thus, slave units A and
B serve to illuminate the subject for a proper exposure while slave unit C
illuminates the background to eliminate shadows. Even with three slave units,
the E-TTL autoflash system controls the flash to obtain a correct exposure.
In addition to setting the A;B flash ratio, a flash ratio of (A:B):C can also be
set. This is done by adjusting slave unit C’s flash exposure compensation
amount.
15 m/49.2 ft
Wireless E-TTL Autoflash With Flash Ratio ON
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