Canon 550EX manual Wireless E-TTL Autoflash With Flash Ratio on

2. Wireless E-TTL Autoflash With Flash Ratio ON

As shown in the figure below, the wireless E-TTL autoflash system described as an example consists of a master unit set to master flash OFF and two slave units.

•The slave ID of the slave unit on the camera’s left is A.

•The slave ID of the slave unit on the camera’s right is B.

•Master flash OFF is set for the master unit.

•The camera (attached with the master unit) and two slave units are properly positioned for the subject.

15 m / 49.2 ft

	10 m /
For indoors A	32.8 ft	B 12 m / 39.4 ft
For outdoors	80°	8 m / 26.2 ft

●Setting the Flash Ratio for Two Slave Units: A and B

With slave unit A being the main flash and slave unit B being the fill flash, the flash ratio (A:B) between these two slave units can be set from 8:1 to 1:1 or from 1:1 to 1:8. (Thirteen 1/2-stop increments.) In terms of stops, the flash ratio can be adjusted from 3:1 to 1:1 or from 1:1 to 1:3. The E-TTL autoflash system then controls the total flash amount according to the flash ratio to obtain a correct exposure.

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