Remote Control - Canon Camera Hackers Manual

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C H A P T E R 5 Scripting
bv = get_bv96()
set_nd_filter(2)
tv = get_tv96()
av = get_av96()
Now, that we have Bv96, Tv96, and Av96, we can compute Sv96 according
to the APEX formula (section 4.2.7). There is one modification here: we al-
low for a user-defined correction value as discussed above. After Sv96 is
computed, the script checks to see whether it exceeds the maximum ac-
ceptable ISO value or is below the minimum possible ISO value. If yes, a
recalculation is performed. Finally, the Sv96 value is set, the camera is fired,
and when the processing is done, the shutter button half-press is released:
sv = av + tv –
bv + compute_corr(tv)
if sv > maxSv then
tv = tv - (sv - maxSv)
sv = av + tv –
bv + compute_corr(tv)
end
if sv < minIso then
tv = tv - (sv - minIso)
sv = av + tv –
bv + compute_corr(tv)
end
set_sv96(sv)
sleep(10)
click("shoot_full")
repeat
sleep(1)
until not get_shooting()
release("shoot_half")
Before running this script, make sure that the values for ND filter and ISO
speed are not overridden in the CHDK Overrides.

5.7.5 Remote control

While CHDK features basic functions for controlling the camera through
the USB port (section 4.9), more sophisticated functionality can be achieved
by combining USB control with a script. Typically, such a script would use
the command get_usb_power to wait for an event from the remote control.