Peabody, you're right, the set_aflock() does nothing if I turn off the display 
Grr!
Do you have a nice solution for an external battery?
No that's not what I meant. aflock should still work with the display off. It does on my camera. But it doesn't prevent the camera from going through the motions of focusing before coming back to where it started.
If I start the script with the display off and the camera in normal autofocus mode, this will set the autofocus based on what's in the frame when it's executed:
sleep 2500
press "shoot_half"
sleep 2500
set_aflock(1)
release "shoot_half"
After that, you can either "shoot_full" or "shoot" for each frame, and the focus will stay locked. I just don't like all the mechanical noise I hear when it's doing that.
An external battery pack could be two C or D cells and a holder for them. Then you would need the right connector for the DC-In socket on the camera. It might be a 2.35 x 0.7 mm connector, which would probably be an EIAJ-01. In the US, that might be available through Radio Shack:
http://www.radioshack.com/product/index.jsp?productId=3807936
