Canon EOS R5 C VR Creator Kit with RF 5.2mm f/2.8 Dual Fisheye Lens - Manual (Page 162)

Canon Speedlites Other Than the EL/EX Series
With an EZ/E/EG/ML/TL series Speedlite set to A-TTL or TTL autoflash mode, the flash
can be fired at full output only.
Set the camera's shooting mode to [
] or [ ] and adjust the aperture value before
shooting.
When using a Speedlite that has manual flash mode, shoot in the manual flash mode.
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