Canon EOS 1DS MARK II 9443A009 Instruction Manual (en)

Sync Speed
The EOS-1Ds Mark II can synchronize with compact, non-Canon flash 
units at 1/250 sec. or slower shutter speeds. With large studio flash, the 
sync speed is 1/125 sec. or slower. Be sure to test the flash to see if it 
synchronizes properly with the camera. 
PC Terminal
The camera’s PC terminal is provided for flash units having a sync 
cord. The PC terminal is threaded to prevent inadvertent 
The camera’s PC terminal has no polarity so you can connect any 
sync cord regardless of its polarity. 
Non-Canon Flash Units
If the camera is used with a flash unit (with dedicated flash contacts) or 
flash accessory dedicated to another camera brand, the camera may not 
operate properly and camera malfunction may result. Also, do not 
connect to the camera’s PC terminal any flash unit requiring 250 V or 
higher voltage. 
Do not attach a high voltage flash unit on the camera’s hot shoe. It might 
not work. 
A Speedlite attached to the camera’s hot shoe and a flash unit connected to 
the PC terminal can be used at the same time.