The Canon EOS 5D Mark III has a maximum video recording time of 30 minutes for all formats. That limit is dependent upon multiple factors like camera settings, media storage size, camera power, and internal camera temperature. See details and notes below for more information.
Maximum continuous video recording times for the Canon EOS 5D Mark III
All Formats & Frame Rates
If the recording time reaches 29 minutes, 59 seconds, recording will stop automatically.
If the file size exceeds 4GB, recording will continue and a new file will be created automatically.
An increase of the camera’s internal temperature may cause recording to stop before the maximum recording time is reached.