This script was designed to enable management of the "dark frame" subtraction process when taking pictures of the night sky. Currently all CHDK cameras take a dark frame image to subtract thermal noise whenever a shot of more than a few seconds in duration is taken. This dark frame takes as much time as the original exposure, so that for every shot of 30 s duration, there will be 30 s of dead time in between while the camera takes and processes a dark frame. This script generally disables the dark frame process but allows a dark frame to be taken very now and then by forcing the shutter to be closed (as determined by the user). This dark frame cam be used to subtract out thermal noise when processing images on a PC.
Running this script requires Lua native calls to be enabled. Use the CHDK Miscellaneous Stuff -> Enable Lua Native Calls? [ * ] menu item. |
Pro Tip : from Alex Varakin on FaceBook CHDK Users Page Ideally, you want to take at least 5 darks and then combine them using median. If you combine them using just average, then you need to take at least 10 darks
forum thread > http://chdk.setepontos.com/index.php?topic=8833.msg92195#msg92195
Note: save this file as meteor.lua
--[[
@title Dark Frame Shooter for Meteors
2010/11/16 original script by fudgey
2012/10/18 modified by waterwingz to shoot continuously and record dark frame periocally
2013/08/28 update to extend shutter speed range from 30 seconds out to 60 seconds
@param n Number of Shots
@default n 1000
@param r Raw On/Off (1=On/0=Off)
@default r 1
@param s Shots per Dark Frame
@default s 50
@param t exposure in seconds (0=auto)
@default t 25
--]]
propcase=require("propcase")
-- Register shutter control event procs depending on os and define functions
-- openshutter() and closeshutter() to control mechanical shutter.
function init()
set_console_layout(5, 0, 40, 14)
-- check for native call interface:
if (type(call_event_proc) ~= "function" ) then
error("your CHDK does not support native calls")
end
local bi=get_buildinfo()
if bi.os=="vxworks" then
closeproc="CloseMShutter"
openproc="OpenMShutter"
if (call_event_proc("InitializeAdjustmentFunction") == -1) then
error("InitAdjFunc failed")
end
elseif bi.os=="dryos" then
closeproc="CloseMechaShutter"
openproc="OpenMechaShutter"
if (call_event_proc("Mecha.Create") == -1) then
error("Mecha.Create failed")
end
else
error("Unknown OS:" .. bi.os)
end
-- close mechanical shutter
function closeshutter()
if (call_event_proc(closeproc) == -1) then
print("closeshutter failed")
end
end
-- open mechanical shutter
function openshutter()
if (call_event_proc(openproc) == -1) then
print("openshutter failed")
end
end
-- switch to record mode if necessary
if ( get_mode() == false ) then
print("switching to record mode")
sleep(1000)
set_record(1)
while ( get_mode() == false) do
sleep(100)
end
end
-- test for still photo rec mode:
rec,vid=get_mode()
if rec ~= true then
error("Not in REC mode")
elseif vid == true then
error("Video not supported")
end
-- make sure we are in P mode
capmode=require("capmode")
if ( capmode.get_name() ~= "P") then
error("Not in Program mode!")
end
-- check that flash is disabled
if ( get_flash_mode() ~= 2) then
error("Flash not disabled!")
end
-- nasty hack to turn seconds into tv96 values
tv96set=0
if (t>=10) then tv96set=-320 end
if (t>=15) then tv96set=-384 end
if (t>=20) then tv96set=-416 end
if (t>=25) then tv96set=-448 end
if (t>=30) then tv96set=-480 end
if (t>=40) then tv96set=-512 end
if (t>=50) then tv96set=-544 end
if (t>=60) then tv96set=-576 end
end -- init()
-- store current exposure params (to be called during half shoot, after autoexposure has finished)
function get_exposure_params()
if( t>=10 ) then
set_prop(propcase.TV,tv96set) -- exposure time
end
tv96=get_prop(propcase.TV) -- exposure time
sv96=get_prop(propcase.SV) -- ISO
if get_nd_present() ~= 1 then -- aperture if camera has iris
--av96=get_av96()
av96=get_prop(propcase.AV)
print("remembering tv=",tv96,"sv=",sv96,"av=",av96)
else
print("remembering tv=",tv96,"sv=",sv96)
end
end
-- set previously saved exposure params (to be called during half shoot, after autoexposure has finished)
function set_exposure_params()
--set_tv96_direct(tv96) -- exposure time
--set_sv96(sv96) -- ISO
set_prop(propcase.TV,tv96) -- exposure time
set_prop(propcase.SV,sv96) -- ISO
if get_nd_present() ~= 1 then -- aperture if camera has iris
--set_av96_direct(av96)
set_prop(propcase.AV,av96)
print("overriding tv=",tv96,"sv=",sv96,"av=",av96)
else
print("overriding tv=",tv96,"sv=",sv96)
end
end
--[[
Exposure parameter controlled shoot: if argument dark==false, function stores
Tv, Av, Sv from this shot and shoots a real photo. If dark==true, function
overrides camera exposure parameters to match previously stored ones and shoots a
dark frame. Obviously one must always call this function with false before it can be
called with true.
--]]
function expcontrol_shoot(dark)
-- half shoot and wait for autoexposure (if disabled, it'll finish real fast)
press("shoot_half")
repeat
sleep(10)
until get_shooting() == true
if dark == true then -- if dark frame
set_exposure_params() -- set overrides
closeshutter() -- close shutter
sleep(10) -- wait for shutter to close (don't know if this is required)
end
-- take the photo
press("shoot_full")
sleep(10)
if dark ~= true then -- normal photo, store exposure params
get_exposure_params()
end
release("shoot_full")
sleep(10)
release("shoot_half")
repeat
sleep(10)
until get_shooting() ~= true
end
-- restore user raw mode and dark frame reduction settings:
function restore()
set_raw(rawmode)
set_raw_nr(dfrmode)
end
-- store user raw mode and dark frame reduction settings
rawmode=get_raw()
dfrmode=get_raw_nr()
-- script starts here
init()
set_raw(r) -- enable RAW or DNG
set_raw_nr(1) -- disable Canon's dark frame reduction
j=s
for i=1,n do
print("shooting RAW+JPG", i, "of",n)
expcontrol_shoot(false) -- shoot a photo, store its exposure params
if j >= s then
j=0
print("shooting a dark frame")
expcontrol_shoot(true) -- shoot dark frame using stored exposure parameters
else
j=j+1
end
end
print("shooting final dark frame")
expcontrol_shoot(true)
restore()
print("done")