I am currently in the African bush photographing leopards with a 1D Mk4.
Many of the shots require fill flash.
The use of a Speedlight locks the ISO at 400.
This limits exposure and shutter speed settings as you require a high shutter speed, more than 500, and depth of field, F5.6 or higher, to capture action shots.
Is there a cure for this?
The guys with the D4 Nikons have no hassles as Auto ISO stays Auto ISO, irrespective of flash usage, the flash listens to the camera and does not dictate to the camera as the Canon flash seems to be doing.
Does the 1DX support ISO for flash usage or does it also enforces ISO 400, meaning that I may have to shop on the dark side??