Canon EOS 5D MARK IV Instruction Manual page 566

Troubleshooting Guide
The manually set ISO speed changes when
switching to movie shooting.
For viewfinder shooting and Live View shooting, the ISO speed
will be set according to the setting of [Range for stills] under
[z2: ISO speed settings] (p.180). For movie shooting, the ISO
speed will be set according to the setting of [Range for movies]
or [Range for H] under [z2: ISO speed settings] (p.379).
The exposure changes during movie shooting.
If you change the shutter speed or aperture during movie
shooting, the changes in the exposure may be recorded.
Shooting a few test movies is recommended if you intend to
perform zooming during movie shooting. Zooming during movie
shooting may result in recording of changes in exposure or
mechanical sound of the lens, or images may be out of focus.
The image flickers or horizontal
stripes appear during movie shooting.
Flickering, horizontal stripes (noise), or irregular exposures can be
caused by fluorescent lighting, LED lighting, or other light sources
during movie shooting. Also, changes in the exposure (brightness)
or color tone may be recorded. In the <s> or <a> mode, a
slow shutter speed may reduce the problem. The problem may be
more noticeable in time-lapse movie shooting.
564