Canon EOS REBEL T7i Instruction Manual page 446

Troubleshooting Guide
The ISO speed cannot be set for movie shooting.
In shooting modes other than <a>, the ISO speed is set

automatically.
In the <a> mode, you can manually set the ISO speed (p.269).
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.
Zooming the lens during movie shooting may cause changes in the

exposure regardless of whether the lens's maximum aperture changes
or not. The changes in the exposure may be recorded as a result.
The subject looks distorted during movie shooting.
If you move the camera to the left or right or shoot a moving subject,

the image may look distorted.
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 <a> mode, a slow shutter speed
may reduce the problem.
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