Canon EOS R50 Mirrorless Camera (White) - Manual (Page 159)

Shutter sync.
Normally, set to [ 1st curtain ] so that the flash fires immediately after shooting starts.
Set to [ 2nd curtain ] and use low shutter speeds for natural-looking shots of subject motion
trails, such as car headlights.
Caution
When using second-curtain synchronization, set the shutter speed to 1/30 sec. or
slower. For shutter speeds exceeding 1/40 sec., first-curtain synchronization is
used automatically even if [
2nd curtain ] is set.
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