HDR Fast Shooter

A Lua script to implement rapid HDR shooting.

There are many HDR (or exposure stacking) scripts on the CHDK wiki and forum. However, many of them are camera specific as they use script driven key presses or set property case values that depend on the OS release of the camera.

Listed below is an HDR script that is camera model independent. It measures what the camera thinks is the correct current exposure and then makes a user specified number of exposures at faster and slower shutter speeds than what the camera specified. Using HDR stacking software on the PC, it will be possible to use some (or all) of these images to create a final high dynamic range image.

The script will take each picture as quickly as the camera will allow. The focus is locked in at the start using a "half press" and the script fires each successive exposure as soon as the camera is ready. Note that you probably want to disable the camera's flash - the actual exposure when the flash fires will ruin the HDR effect.

This script should work on every CHDK equipped camera - contains no camera specific key presses or property case settings. Remember to save with the .lua file name extension ( e.g.fastHDR.lua ).

​--[[
 @title HDR Fast Shooter
 @param n Number of Steps
 @default n 5
 @param s tV step size
 @default s 96 
 --]]

 -- restore user raw mode and dark frame reduction settings:
 function restore()
    set_aflock(0)
 end

 -- setup 
 set_console_layout(10, 0, 40, 14)
 props=require("propcase")
 propset=get_propset()
 pTV=props.TV
 if( propset > 3) then pTV2=props.TV2 end
 print("Started...")


 -- make sure we are in shooting mode
 if ( get_mode() == false ) then
   sleep(1000)
   set_record(1)
   while ( get_mode() == false) do
       sleep(100)
   end
  sleep(1000)
 end

 -- timestamp the start
 z = get_day_seconds()

 -- focus and get exposure
 press("shoot_half")
 repeat
     sleep(50)
 until get_shooting() == true	
 set_aflock(1)
 tv96val=get_tv96()-(n*(s/2))

 -- take the shots as fast as possible
 for i=1, n, 1 do
    print("step=", i, "tv96=", tv96val)
    ecnt=get_exp_count()
    set_prop(pTV,tv96val)
    if( propset > 3) then set_prop(pTV2,tv96val) end
    press("shoot_full_only")
    repeat
      sleep(20)
    until(get_exp_count()~=ecnt)
    release("shoot_full_only")
    tv96val = tv96val+s
 end

 -- all done so cleanup
 z = get_day_seconds() -z
 print("...done in", z, "seconds")
 restore()

Original Version

• runs 50% slower than the version shown above

--[[ 
@title HDR Medium Fast Shooter 
@param n Number of Steps 
@default n 5 
@param s tV step size 
@default s 96  
--]] 
function fastshoot(a1,s1,t1)
  set_av96(a1)
  set_sv96(s1)
  set_tv96_direct(t1)
  press("shoot_full_only")
  repeat 
     sleep(50)
  until get_shooting() == true	
  release("shoot_full_only")
  repeat
     sleep(50)
  until get_shooting() == false
end
set_console_layout(10, 0, 40, 14) 
print("Started...")
if ( get_mode() == false ) then
 sleep(1000)
 set_record(1)
 while ( get_mode() == false) do
     sleep(100)
 end
end
sleep(1000)
press("shoot_half") 
repeat
  sleep(50)
until get_shooting() == true 
release("shoot_half") 
repeat
sleep(50)
until get_shooting() == false
set_aflock(1)
av=get_av96() 
sv=get_sv96() 
tv=get_tv96() 
print( "av96=", av, "sv96=", sv, "tv95=", tv )
tv96val=tv-n*s/2
for i=1, n, 1 do
   print("step=", i, "tv96=", tv96val)
   fastshoot(av,sv,tv96val)
   tv96val = tv96val+s
end
set_aflock(0)
print("...done")