Canon MACRO RING LITE MR-14EX II Mode D'emploi page 47

Advanced multiple flash shooting with slave A, B, and C added
(p.53)
This section describes multiple flash shooting with slave C where
slave A and B are also added. Slave A is controlled to fire with flash
tube A and slave B to fire with flash tube B as a group (as a single
flash unit).
Shooting with firing group C pointed directly toward the main subject may
result in overexposure.
Before shooting, perform a test flash (p.18) and test shooting.
To avoid interfering with transmission, do not place any obstacles
between the master unit and slave units.
Position the sensor of the slave unit pointed toward the master unit, using
the mini stand provided with the slave flash unit.
When shooting indoors, since the transmission signal is reflected off the
walls, operation may be possible even with slightly imprecise positioning.
C
A
B
: Wireless Multiple Flash Shooting
45