Sync speed priority - what does it do?

[Bazsl]

Can anyone explain what Sync Speed Priority does? I would like to have a better understanding so I can predict whether to use it or not in a particular situation. The only negatives in the manual are shown below and they are not very enlightening. Thanks.

[p4pictures]

Sync speed priority allows the camera sync speed to be faster than otherwise possible when certain conditions are met.

Conventionally the flash sync speed with electronic shutter mode is 1/180s but sync speed priority will allow 1/200s to be used, and if crop mode is selected the sync speed is 1/320s.

Basically you need to use specific Canon Speedlites listed in the manual - make sure to expand the note.

https://cam.start.canon/en/C017/manual/html/UG-03_Shooting-1_0100.html 

In my view sync speed priority is helpful when shooting in 1.6x crop mode, and if you are trying to maximise the shutter speed to balance the flash with the ambient light in a scene.