Canon 550 EX - Manual (Page 66)

Wireless E-TTL Autoflash With Flash Ratio ON
● 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.
66
For indoors
For outdoors
15 m / 49.2 ft
10 m / 32.8 ft
12 m / 39.4 ft B
C
A
8 m / 26.2 ft
80°
05. F073-E (51~) 02.4.1 2:12 PM Page 66