Canon MARK IV User Manual (en)

Troubleshooting Guide
If you use a flash unit other than an EX-series Speedlite, the flash will 
always be fired at full output (p.120).
When the [Flash metering mode] flash Custom Function is set to 
[TTL (autoflash)], the flash will always be fired at full output (p.124).
If flash exposure compensation has already been set with the Speedlite, 
flash exposure compensation cannot be set with the camera. When the 
Speedlite’s flash exposure compensation is canceled (set to 0), flash 
exposure compensation can be set with the camera.
Set [8C.Fn I -15: Flash sync. speed in Av mode] to [0: Auto
For Live View shooting, use a memory card (a hard disk-type card is 
not recommended). A hard disk-type card requires a lower temperature 
range for operation than memory cards. If the temperature gets too 
high, the Live View shooting may stop temporarily to prevent damage 
to the card’s hard disk. When the camera’s internal temperature 
decreases, you can resume Live View shooting (p.139).
Set [LV z/k set.] to [Stills] (p.126).
During Live View shooting, the shutter will make two sounds when you 
take a picture (p.127).
The flash always fires at full output.
Flash exposure compensation cannot be set.
High-speed sync cannot be set in the Av mode.
Live View shooting is not possible.
During Live View shooting, the ISO speed, shutter speed, and 
aperture cannot be set.
The shutter makes two shooting sounds during Live View shooting.