Canon EOS 90D DSLR Camera with 18-135mm Lens - Manual (Page 175)

175
Flash Function Settings
 Wireless functions
You can use radio or optical wireless
transmission to shoot with wireless multiple-
fl ash lighting.
For details on wireless fl ash, refer to
the Instruction Manual of a Speedlite
compatible with wireless fl ash photography.
 Firing ratio control
With a macro fl ash, you can set the fi ring
ratio control.
For details on fi ring ratio control, refer to
the macro fl ash’s Instruction Manual.
 Flash zoom (Flash coverage)
With Speedlites having a zooming fl ash
head, you can set the fl ash coverage.