S9100 - Autofocus Mode if Stepping into a Shot

When my S9100 is tripod mounted, if using the Self-Timer and I'm stepping into the shot is there any value in having the autofocus set to Full-Time? Will it include me in its focusing or is that determined at the moment I press the button right down, even when on Self-Timer? I've experimented but not sure if I can tell the difference. I’d appreciate any advice on this point.