Canon EOS 5D Mark III Video Recording Limits
|All Formats and Frame Rates||30 minutes1|
1 If the recording time reaches 29 minutes and 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.
Source: Canon 5D Mark III Instruction Manual (English) - pages 226, 232, & 233