Canon Macro Twin Light MT-26EX-RT Instruction Manual page 72

a: Multiple Flash Photography with Slave C Added
LCD Panel Illumination
During radio transmission wireless multiple flash shooting, the master
unit's LCD panel illuminates or turns off according to the charge status
of the master unit and slave units (firing groups).
The master unit's LCD panel illuminates if the master unit and slave
units are not fully charged. When the master unit and slave units are
fully charged, the LCD panel illumination will turn off after approx. 12
sec.
When the charging of the master unit and slave unit starts as you take
pictures, the master unit's LCD panel will be illuminated again.
If the master unit or any of the slave units (firing group) are not fully charged,
<G> will be displayed on the master unit's LCD panel. Check that
<G> is not displayed on the LCD panel, and take a picture.
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