Canon EOS REBEL T7i Instruction Manual page 210

D Using an External Speedlite
Canon Speedlites Other Than the EX-series
With an EZ/E/EG/ML/TL-series Speedlite set to A-TTL or TTL

autoflash mode, the flash is fired at full output at all times.
Set the camera's shooting mode to <a> (manual exposure) or
<f> (aperture-priority AE) and adjust the aperture setting before
shooting.
When using a Speedlite that has manual flash mode, shoot in the

manual flash mode.
Using Non-Canon Flash Units
Sync Speed
The camera can synchronize with compact, non-Canon flash units at
1/200 sec. or slower shutter speeds. Use a sync speed slower than
1/200 sec.
Be sure to test the flash unit beforehand to make sure it synchronizes
properly with the camera.
Cautions for Live View Shooting
A non-Canon flash will not fire during Live View shooting.
If the camera is used with a flash unit or flash accessory dedicated to

another camera brand, the camera not only may not operate properly,
but malfunction may result.
Do not attach a high-voltage flash unit to the camera's hot shoe. It may

not be fired.
210