Hi,

I am using a canon SX230, and have installed chdk on its 15 Gb SD card. (I have to make a 'firmware update' to load chdk when I turn the camera on).

CONFIGURATION:
I am trying to capture a slow phenomenon (growth of bacteria on a petri dish over a timescale of a few days). I want to take pictures every 20 min. I have also an AC power supply adaptor, so that the SX230 can run over very long periods without power supply shortage.

I cannot use a simple timelapse script, because the lighting on the petri dish needs to be turned off between shootings (too much heating if left on).

I am using an Arduino microcontroler to repeatedly (a) turn light on (b) generate a 1 second 5V pulse on the usb input of the camera so as to trigger picture shooting , (c) turn light off (d) wait then cycle back to step(a).

I enabled "remote" on chdk setting, 1 push; I load the script CHDK\SCRIPTS\EXAM\remote.bas.

With chdk loaded (and not in the 'alt' mode), I put the camera under manual setting for iso, speed, and focus distance; I also adjust zoom to the desired value, and set 'on' the automatic LCD turn off.
The LCD automanic shut off is important to avoid too much heating of the SX230.

Left in the standard mode (not in the 'alt' mode), the triggering (made by the Arduino) works nicely to shoot automatically at chosen time intervals

PROBLEM:
Things appears to go smoothly, BUT:
When looking at the series of pictures taken over few days, it appears that the focus is not steady from one picture to the other. 🙁
Would someone have an idea of why this occurs ????

ALTERNATE ASSAY:
I have written a small script, so as to force a fixed value of focus, and make this script the one to be executed, in the chdk settings.
remot1.bas:

@title Remote button

while 1
wait_click 1
if is_key "remote" then gosub "Foo"
wend

end

:Foo
set_focus 247
rem set zoom 35 (zoom setting does not seem to work on the SX230)
shoot
print get_focus
print get_zoom

return

* * * * *
After that I have loaded chdk via firmware update, I get out of the 'alt' mode so as to set the value of the zoom, and extend the lens out; at that time, I get the message "interrupted".

PROBLEM:
after that manual setting of the zoom,
the script only works when I leave the SX230 in th 'alt' mode. (Otherwise, shooting is indeed triggered, but apparently without going through the above script remot1.bas. (no printed values, and no proper focus).

Why is that ??? What is the way to go ?

(I would not mind leaving the chdk running, but I would then need tu turn on and off the LCD so that the SX230 does not heat too much.)

Thanks for the help!