I was wondering, though, if there was a way to make the cameras take 3 photos (at normal exposure, +1, and -1) in quick succession (ie. bracketing, so I can create an HDR w/ more dynamic range than the standard jpg or even RAW).
This isn't directly supported in multicam. However, you could use normal CHDK bracketing with set_config_value, something like this:
!mc:cmdwait('call local cnf_core=require"gen/cnf_core" set_config_value(cnf_core.bracket_type,3) set_config_value(cnf_core.tv_bracket_value,3)')
!mc:shoot({cont=true, shots=3})
Breaking this down:
cnf_core=require... loads friendly names for the set_config_value parameters.
set_config_value(cnf_core.bracket_type,3) sets the bracket type to +/-
set_config_value(cnf_core.tv_bracket_value,3) sets the bracket value to 1 stop.
!mc:shoot({cont=true, shots=3}) shoots a burst of 3 shoots, in continuous mode
if it's enabled in the canon UI. You'll need to enable continuous mode on each camera in the Canon UI or with the UI property functions.
You can find the available parameter names by loocking at CHDK/LUALIB/GEN/cnf_core.lua
To know what the values are, you can change them on one camera using the CHDK menu and read back the values with get_config_value.
I'll look into adding bracketing as a multicam feature, it's been on my list of useful things to add for a while.
I know using mc:shoot and mc:testshots I can define specific aperture, ISO, and shutter speed parameters, but I was hoping to use the exposure from each camera to set these variables automatically (as each camera may require slightly different settings).
Note that you can set camera specific values with the latest multicam. See here
https://chdk.setepontos.com/index.php?topic=13917.msg141971#msg141971So you could half press, read all the exposure values from each camera, and then bracket by modifying them between shots. I can provide more detailed examples if you want to use this approach.
