Canon EOS 5D MARK IV Instruction Manual page 163

With the Digital Lens Optimizer set:
When [Digital Lens Optimizer] is set to [Enable], the
continuous shooting speed will greatly decrease.
The maximum continuous shooting speed will vary depending on
the shooting conditions. For details, see page 162.
i : Low-speed continuous shooting
While you hold down the shutter button completely, you can shoot
continuously at approx. 3.0 shots/sec. maximum.
During Live View shooting, if [AF operation] is set to [Servo AF],
priority will be given to focus tracking on the subject (Subject-
tracking priority) with a maximum continuous shooting speed of
approx. 3.0 shots/sec.
B : Silent single shooting
You can perform single shooting while suppressing the mechanical
sound during viewfinder shooting. This cannot be set for Live View
shooting.
M : Silent continuous shooting
You can shoot continuously at approx. 3.0 shots/sec. maximum
while suppressing the mechanical sound during viewfinder
shooting (as compared to the <i> setting). This cannot be set for
Live View shooting.
Q : 10-sec. self-timer/remote control
k: 2-sec. self-timer/remote control
For self-timer shooting, see page 163. For remote control shooting,
see page 279.
i Selecting the Drive Mode
161