Canon EOS 77D User Manual - Page 240

Custom Wireless Flash PhotographyN Setting the Flash Output Manually for Wireless Flash Photography When [Flash mode] is set to [Manual flash], flash exposure can be set manually. The flash output settings that can be set ([1flash output], [Group A output], etc.) vary depending on the [Wireless func.] setting (see below). [Wireless func.: 0]  [Firing group: 1All] The manual flash output setting is applied to all the external Speedlites.  [Firing group: 1(A:B)] You can set the flash output separately for slave groups A and B. [Wireless func.: 0+3]  [Firing group: 1All and 2] The flash output can be set separately for the external Speedlite(s) and built-in flash.  [Firing group: 1(A:B)2] You can set the flash output separately for slave groups A and B. You can also set the flash output for the built-in flash. 240