Canon EOS Rebel SL1 18-55mm IS STM Kit Instruction Manual - Page 300

3 Custom Function SettingsN Custom Functions are organized into four groups based on the function type: C.Fn I: Exposure, C.Fn II: Image, C.Fn III: Autofocus/Drive, C.Fn IV: Operation/Others. C.Fn I: Exposure C.Fn-1 Exposure level increments 0: 1/3-stop 1: 1/2-stop Sets 1/2-stop increments for the shutter speed, aperture, exposure compensation, AEB, flash exposure compensation, etc. This is effective when you prefer to control the exposure in less fine increments than 1/3-stop increments. With setting 1, the exposure level will be displayed in the viewfinder and on the LCD monitor as shown below. C.Fn-2 ISO expansion 0: Off 1: On When you set the ISO speed, you will be able to set "H" (equivalent to ISO 25600) for still photos and "H" (equivalent to ISO 12800) for movies. Note that if [C.Fn-3: Highlight tone priority] is set to [1: Enable], "H" cannot be set. 300