On Thu, 19 Nov 1998 12:54:32 -0600, "EOS A2E" wrote:

>What is the 2nd curtain sync function?

The flash can be fired at any time the shutter is
fully open, which it is at any shutter speed up to
the flash "sync" speed. This includes just after
the 1st curtain fully opens the shutter, or just
before the 2nd curtain closes the shutter. At the
sync speed, the 1st and 2nd curtain times are almost
the same, but at slow speeds, they are almost as far
apart as the (long) shutter speed duration.

> What does it do?

See above...

>Under what circumstances do I use this function?

With slow exposure speeds and enough ambient light,
moving images can look better with the motion blur
on the logical side of motion direction of subjects
rendered sharp by the flash part of the exposure.
It is also useful when shooting people at slow speeds,
since the (surprising) flash occurs at the end of the
exposure, reducing (on film...;-) reaction effects.

>Should I always have it enabled?

Yes, unless it adversely affects camera exposure modes
in some way.