Canon EOS 1D Instruction Manual page 174

3 Custom Function Settings
C.Fn IV -4
You can assign a frequently-used function to <0>. When the camera is
ready to shoot, you can press <0>.
0: Normal (disabled)
1: White balance
While looking at the rear LCD panel, you can change the WB.
2: Image size
While looking at the rear LCD panel, you can change the memory card
and image size.
3: ISO speed
While looking at the top LCD panel or in the viewfinder, you can change
the ISO speed.
4: Picture Style
The [1 Picture Style] menu will appear.
5: Record func. + media/folder
The [5 Record func+media/folder sel.] menu will appear.
6: Menu display
Gives the same function as the <M> button.
7: Image playback
Gives the same function as the <x> button.
If the [Live View shoot.] menu has been set to [Enable], the Live View
shooting will override any setting from 1 to 7 above. Pressing <0> will
show the Live View image instead.
C.Fn IV -5
0: Tv=6/Av=5
1: Tv=5/Av=6
Convenient when you use studio flash and frequently change the
aperture. Also, when you use AEB in the manual exposure mode, the
shutter speed can stay fixed while only the aperture is shifted for AEB.
The shutter speed can also be set by pressing the <O> button and
turning the <6/5> dial.
174
SET button when shooting
Tv/Av setting for Manual exposure