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This script uses the camera's neutral density (ND) filter to achieve two different exposure levels for the same scene. Conventional HDR scripts vary exposure by changing shutter speed, lens aperture or ISO sensitivity setting - each of which changes the image somewhat between each shot (blur, DOF, grain). Using the ND filter allows both shot to be at identical settings for better matching during image stacking.
The script should run on any CHDK equiped camera that has an ND filter. It does not use key presses or propset values.
The only adjustment available is an exposure offset. The script first takes a picture with normal exposure settings and then inserts the ND filter and takes a second shot with the same exposure settings. The second shot will always be darker than the first. You might need to adjust the normal exposure level if this sequence does not work for you.
Info on ND filter : http://chdk.wikia.com/wiki/ND_Filter
CHDK forum thread > http://chdk.setepontos.com/index.php?topic=9558
--[[ @title ND Filter HDR @param e Exposure Offset (stops) @default e 0 @range e -4 4 --]] -- release AF lock on exit function restore() set_aflock(0) set_nd_filter(0) end -- setup set_console_layout(1, 0, 45, 12) print("ND HDR started...") if (get_nd_present()==0) then print("Note : ND filter not present?") else -- switch to shooting mode if ( get_mode() == false ) then sleep(1000) set_record(1) while ( get_mode() == false) do sleep(100) end end sleep(200) -- check exposure and focus print("shoot half") press("shoot_half") repeat sleep(50) until get_shooting() == true set_aflock(1) release("shoot_half") repeat sleep(50) until get_shooting() == false av=get_av96() sv=get_sv96() tv=get_tv96() print( "start tv=", tv, "av=", av, "sv=", sv, "offset=",e*96 ) -- shoot twice print("shot 1 .. ND filter out") set_nd_filter(2) set_tv96_direct(tv+e*96) set_av96_direct(av) set_sv96(sv) shoot() print("shot 2.. ND filter in") set_nd_filter(1) set_tv96_direct(tv+e*96) set_av96_direct(av) set_sv96(sv) shoot() end restore() print("...done")