There is some confusion about the max safe sync voltage. The cameras owners manuals is not clear on this matter leaving some to believe that the 250v (on newer DLSRs) is only safe for the PC socket with the hotshoe still at 6v like the older cameras. I would think that they share the same circuit and 250v is safe for the hotshoe also
In Canon EOS cameras, the PC socket and Hotshoe both use the same circuit and are both safe up to the same max voltage.
This was confirmed by Chuck Westfall of Canon U.S.A. in March 2007.
The trigger circuit voltage (TCV) rating for any EOS SLR is the same on the hot shoe as it is on the PC terminal (if the camera has one), but the acceptable TCV level varies according to the camera model. Incidentally, the main reason for the difference is the way the X-sync signal is generated. With the 250V cameras, the X-sync signal is generated electronically. With the 6V cameras, the X-sync signal is generated mechanically. There are no guarantees, but going forward I anticipate that most if not all future EOS SLRs will be safe for TCV up to 250 volts.
They are rated for 250v max voltage. If you have any concern, we highly recommend the use of a SafeSync.
09/26/2023: New firmware updates are available.
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07/31/2023: New firmware updates are available.
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03/30/2023: New firmware updates are available.