Canon EOS 7D Mark II (G) Instruction Manual page 280

Using Wireless FlashN
[ (A:B C)] Multiple slave units in multiple groups
1
C
A
If [Firing group] is set to [1(A:B)], the slave units in firing group C will
not fire.
If firing group C is pointed toward the main subject, overexposure may
result.
280
This is a variant of the [1(A:B)] setup.
This setup has group C eliminating the
background shadows created by groups
A and B.
Refer to the Speedlite's instruction
manual and set three slave units to firing
B
group A, B, and C, respectively. Position
the Speedlites as shown in the
illustration.
Set [Firing group] to [1(A:B C)].
1
Set the A:B flash ratio and the
2
flash exposure compensation
amount for C, then shoot.
Select [A:B fire ratio] and set the
flash ratio.
Select [Grp.C exp. comp.] and set
the flash exposure compensation
amount.