Canon EOS Rebel T6s EF-S 18-135mm IS STM Lens Kit Instruction Manual - Page 100

f: Changing the Autofocus OperationK AF Points Lighting Up in Red By default, the AF points light up in red when focus is achieved in lowlight conditions. In Creative Zone modes, you can set whether to have the AF points light up in red when focus is achieved. AF-Assist Beam with the Built-in Flash Under low-light conditions, when you press the shutter button halfway, the built-in flash may fire a brief burst of flashes. This illuminates the subject to help autofocusing. 100