CHDK Manual Focus and Subject Distance Overrides

Subtitle :  Getting the "set_focus()" command in CHDK scripts,  or the "Override Subject Distance" menu item in the Enhanced Photo Operations menu,  to work.

set_aflock()

• set_aflock(1) causes the Canon firmware to stop focussing when shooting

• does an initial focus measurement and sets focus at that value when called

• set_aflock(0) restores camera automatic focussing.
• seems to works on almost all cameras
• using set_aflock() may be necessary on some camera for set_focus() to work (elph310). On other cameras, it has no effect on whether set_focus() works.
• on some cameras,  the set_aflock() command must be issued after a "half-press" focus completes and before the half press is released
• if you call set_aflock() and then set_focus() (in a mode on your camera where that works) then the focus for all subsequent shots will stay at the value specified in set_focus().  If set_aflock() has not been called then set_focus() will only apply to the next shot - after that the camera will revery to auto focus.

set_focus()

• script command that may or may not actually set the focus setting (in mm) the next time the camera shoots.
• on some cameras, set_focus() will only work if the camera is in Canon AFL mode (ex: A1200)
• on some cameras, set_focus() will only work if the camera is in Canon MF mode (ex: SX50HS)
• on some cameras, set_focus() will work when set_aflock(1) has been called (ex: elph310)
• on some cameras, set_focus() will only work when the camera is in P mode (or at least not in AUTO)
• on some cameras, set_focus works every time regardless of mode (ex: G10, SD940)

Notes :

1. Canon AFL mode is typically achieved via simulated button presses using click() - see your camera manual for the correct sequence. May require holding a "half press" while another key is clicked.
2. Canon MF mode is may be achieved via simulated button presses, post_levent_for_npt call, and/or call_event_proc calls.
3. When in Canon MF mode,  focus will be set immediately when a set_focus() command is issued.  Otherwise the focus will not take effect until after the "half-pres" part of the shooting sequence.

Forum Links

http://chdk.setepontos.com/index.php?topic=9533.0

http://chdk.setepontos.com/index.php?topic=8016.msg94251#msg94251

http://chdk.setepontos.com/index.php?topic=6672.msg75166#msg75166

Test Script

--[[
@title MF Test Suite

@param     f MF Mode
@default f 0
@values  f None AFlock AFL MF1 MF2 MF3
--]]

set_console_layout(1 ,1, 45, 14 )
print( "f-tester v1/2")
sleep(1000)
if ( get_mode() == false ) then
    set_record(1)
    while ( get_mode() == false ) do sleep(100) end
end

if( f==1) then            -- set_aflock()
    print("aflock mode")
    set_aflock(1)
end

if( f==2) then            -- enable Canon AFL lock focus via key presses 
    print("AFL mode")
    local count = 0
    local timeout = false
    press("shoot_half")
    repeat  
        sleep(50)
        count = count + 1
        if (count > 40 ) then timeout = true end        
    until (get_focus_ok() == 1 ) or (timeout == true) 
    if (timeout == true) then print("Warning : focus attempt timed out")
    else  click("left")
    end
    sleep(100)
    release("shoot_half")
end


if( f==3) then             -- MF1 lock focus via key presses 
    print("MF1 mode")
    click("up")
end

if( f==4) then             -- MF2 lock focus using levent for key press
    print("MF2 mode")
    post_levent_for_npt("PressSw1AndMF") 
end

if( f==5) then             -- MF3 lock focus using event_proc for key press  
    print("MF3 mode")
    call_event_proc("SS.Create")
    call_event_proc("SS.MFOn")
end

sleep(1000)
print("Focus state=".. get_focus_mode())
for focus=100,300,100  do
    set_focus(focus)
    sleep(2000)
    press("shoot_half")
    sleep(1000)
    before=get_focus()
    click("shoot_full")
    release("shoot_half")
    after=get_focus()
    if ((focus-after)/5 == 0) then fstr=" : okay" else fstr=" : fault" end
    print("Set:"..focus," Before:"..before," After:"..after..fstr)
    sleep(2000)
    press("shoot_half")
    sleep(1000)
    before=get_focus()
    click("shoot_full")
    release("shoot_half")
    after=get_focus()
    if ((focus-after)/5 == 0) then fstr=" : locked" else fstr=" : unlocked" end
    print("    "..focus," Before:"..before," After:"..after..fstr)
    sleep(1000)
end