12-17-2018 12:34 PM - edited 12-17-2018 03:17 PM
The M100 by itself can not operate as a "Master" to any Canon "Slave" flash.
12-17-2018 02:04 PM
12-17-2018 03:00 PM
It seems there is no solution for the M100 unfortunately
"While the camera does feature a built-in pop-up flash, the pop-up flash does not have the ability to communicate with Canon Speedlite flashes"
12-17-2018 03:01 PM - edited 12-17-2018 03:26 PM
I didn't realize that the M100 had no hotshoe. It will be impossible to trigger your 270EX.
There are many 3rd party flash units with a built-in optical slave that CAN be triggered by the built-in flash of your M100.
The $80 Yongnuo 565EX III is one example.
12-17-2018 03:37 PM