Canon 5246B002 Instruction Manual page 32

Manual FlashN
You can set the flash output from 1/64 power to 1/1 full power in 1/3-
stop increments. Use a hand-held flash meter to determine the required
flash output to obtain a correct flash exposure. Setting the camera's
shooting mode to <f> or <a> is recommended.
30
Select [Flash mode].
1
Select [Flash mode] and press
<0>.
Select [Manual flash].
2
Select [Manual flash] and press
<0>.
Set [1flash output].
3
Select [1flash output] and press
<0>.
Set the flash output and press <0>.