Canon EOS Rebel T6i EF-S 18-55mm IS STM Lens Kit Instruction Manual - Page 248

3 Menu Function Settings Z1 When you set the power switch to , the [Z1] and [Z2] tabs will show functions dedicated to movie shooting.  AF method The AF methods are the same as described on pages 206-213. You can select [u+Tracking], [FlexiZone - Multi], or [FlexiZone - Single].  Movie Servo AF During movie shooting, the camera focuses on the subject continuously. The default setting is [Enable]. When [Enable] is set:  The camera focuses on the subject continuously even when you are not pressing the shutter button halfway.  Since this drives the lens continuously, it will consume battery power and shorten the total possible movie shooting time (p.235).  With certain lenses, the lens mechanical sound during focusing may be recorded. If this happens, use the Directional Stereo Microphone DM-E1 (sold separately) to reduce the lens mechanical sound in the movie. Also, using certain STM lenses (for example, the EF-S18-55mm f/3.5-5.6 IS STM) will reduce lens operation noise.  If you want to set the lens's focus mode switch to during Movie Servo AF, first set the power switch to . 248