3Custom 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. 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 Flash sync. speed in Av mode
When you use flash in the aperture-priority AE mode (f), you can set the flash sync speed.
0:Auto
The flash sync speed is set automatically within a range of 1/200 sec. to 30 sec. to suit the scene’s brightness. With an external Speedlite, high- speed sync will also be possible.
1:1/200-1/60 sec. auto
Prevents a slow shutter speed from being set in low-light conditions. It is effective for preventing subject blur and camera shake. However, while the subject will be properly exposed with the flash, the background may come out dark.
2:1/200 sec. (fixed)
The flash-sync speed is fixed to 1/200 sec. This more effectively prevents subject blur and camera shake than with setting 1. However, the background may come out darker than with setting 1.
When 1 or 2 is set, high-speed sync cannot be used with an external Speedlite.
