Canon EOS 30D Instruction Manual page 170

3 Custom Function SettingsN
C.Fn-06
0: 1/3-stop
1: 1/2-stop
Sets 1/2-stop increments for the shutter speed, aperture, exposure
compensation, AEB, etc.
The exposure level will be displayed in the viewfinder and on the LCD
panel as shown below.
C.Fn-07
You can enable the built-in flash, external Speedlite, and non-Canon
flash connected to the PC terminal to fire.
0: Fires
1: Does not fire
This will disable the flash, but the AF-assist beam will still be
emitted. Note that whether or not the AF-assist beam is emitted is
dependent on the C.Fn-05 setting.
C.Fn-08
0: Off
1: On
For the ISO speed, "H" (equivalent to ISO 3200) will be selectable.
170
Exposure level increments
Flash firing
ISO expansion