Canon EOS 40D - Manual (Page 103)

103
The built-in flash and external Speedlite can also be set with the menu.
The menu for the external Speedlite will be applicable only to EX-series
Speedlites whose functions can be set with the camera.
Select [Flash control].
Under the [6] tab, select [Flash
control], then press <0>.
X The flash control screen will appear.
Normally, set this to [Enable].
If [Disable] is set, both the built-in
flash and external Speedlite will not
fire. This is good when you only want
to use the AF-assist beam.
[Flash mode] cannot be selected.
[Flash exp. comp] can be set as
explained on page 101.
Set [E-TTL II] as explained on the
next page.
Shutter sync.
Normally, set this to [1st curtain] so that the flash fires immediately
after the exposure starts.
If [2nd curtain] is set, the flash will fire right before the exposure
ends. When this is combined with a slow sync speed, you can create
a trail of light such as from car headlights at night. With 2nd curtain
sync, two flashes will be fired. Once when you press the shutter
button completely, and once immediately before the exposure ends.
3 Flash ControlN
[Flash firing]
[Built-in flash func. setting]