Yes, waterwingz is the greatest. I learned a lot of what I know about CHDK from his posts, and also how much I don't know!
@title Intervalometer
@param a = interval (sec)
@default a 5
if get_mode = 0 then goto "in_rec"
sleep 1000
set_record 1
:wait_rec
sleep 100
if get_mode <> 0 then goto "wait_rec"
:in_rec
a=a*1000
do
s = a+get_tick_count
shoot
do
set_backlight 0
sleep 50
until (s <= get_tick_count)
until ( 0 )
:restore
set_backlight 1
end
This should improve things a little as far as the backlight is concerned. Canon keeps turning the backlight back on with every shot, so you need to turn it off repeatedly to minimize the on time and battery drain. It still flashes briefly no matter what, which tells you that it's working at least.
One problem with this script is that it takes brightness measurements, changes exposure, and then sets the focus before each picture. This takes a lot of time, and drains the battery running the focus motors. Also, the time lapse may rapidly change exposure and "flash" as the camera swings around pointing at dark and light places.
I've been experimenting with doing time lapse all with "half_shoot" pressed. Try it without CHDK. Point the camera at something, press the shutter half way, then point the camera at something else. Press the shutter down full, but only let it up half way, not all the way. Then move the camera and take more pictures, always keeping the shutter half way down between pictures. It should hold the focus and exposure between shots.
What you're pointing at with the first half press is critical, since it sets the exposure and focus for the entire time lapse. For your balloon ascent, the focus would be set as close as possible, but with infinity still in focus. This is called the "hyperfocal distance."
If you're interested, I'll see if I can do a Lua program that does this. In the meantime, try my CShooter.lua script, which does this, but takes pictures in continuous drive mode at about 3 pictures per second for your camera. I can modify this script to take pictures at different rates.
You don't need to change the "default" in the script. After booting CHDK, press <alt> and then <set> twice. Load the desired script. Then scroll down to the parameter you want to change (down key), and use the left/right keys to set the value, i.e. 5 seconds.
Oops, here's the CShooter.lua link:
http://chdk.setepontos.com/index.php?topic=8971.msg93459#msg93459
