In selecting high speed sync on my 430EX (and also on a 430EXii) I press the high speed sync button so that the high speed sync icon is shown in the flash unit LCD panel. According to page 16 of the 430EX and 430EXii manuals, you "check to see that the high peed sync icon is shown in the viewfinder."
However, "If you set a shutter speed that is the same or slower than the camera's maximum flash sync speed the (high speed sync icon) will not be displayed in the viewfinder."
My question is: if the camera is set at a shutter speed that is the same or slower than the camera's maximum flash sync speed and the HSS icon is not being shown in the camera viewfinder, is the camera firing in HSS mode or has it reverted to standard sync?
The standard sync will, of course, provide full power firing while the multiple bursts in HSS will provide reduced power.