Thin Lens Functionalised Focus

TLFF.lua

--[[
@title TLFF
@chdk_version 1.6

#log = 0 "Log?" {Off On}

Notes: 
* This test script only runs on the M3, M10 or M100 with the XIMR version of CHDK. But note, not tested on the M100.
* Go to https://drive.google.com/drive/folders/1drk1xi6kMMIeF5xSqXgnpjGCffF8CVkd?usp=sharing for XIMR builds
* 
* The script is a proof of principle of using a thin lens approximation to estimate focus distance from the sensor plane

Release 0.51 ALPHA
photography.grayheron.net
July 2022
--]] 

bi = get_buildinfo()

set_exit_key("down") -- change as required

set_console_autoredraw(1)
set_console_layout(0,0,45,3)

focus_count = -999
reset_lens = false
INF = 999000 -- infinity trap
count = 0
U = 0

-- Check a couple of things first

if not ((bi.platform == "m3") or (bi.platform == "m10") or (bi.platform == "m100")) then 
    print("Doesn't run on this Cam")
    sleep(3000)
    return
end

if get_gui_screen_width() ~= 360 then 
    print("Need an XIMR build")
    sleep(3000)
    return
end

-- Functions --

function units(xx) -- pretty print of focus distance
  local xr =""
  if xx:int() > 5000 then 
      xr=(xx/1000):tostr(1).."m"
  elseif xx:int() > 1000 then 
      xr=(xx/10):tostr(0).."cm"
  else
      xr=(xx):tostr(0).."mm"
  end
  return xr
end
  
function get_focus_distance_lower() -- returns lower focus distance in mm, but note 'accuracy' is 1cm from Canon
  local  x=-1
  if (bi.platform=="m3") and (bi.platsub=="101a") then
    x=peek(0x00244918, 2)
  elseif (bi.platform=="m3") and (bi.platsub=="120f") then
    x=peek(0x0024495C, 2)
  elseif (bi.platform=="m3") and (bi.platsub=="121a") then
    x=peek(0x0024495C, 2)
  elseif (bi.platform=="m10") then -- same address in 110d, 110f, 110g
    x=peek(0x00272018, 2)
  elseif (bi.platform=="m100") and (bi.platsub=="100a") then
    x=peek(0x001FC7FC, 2)
  else
    print('Wrong platform')
  end
  if x == -1 then return -1 else return x*10 end -- in mm
end

function get_focus_distance_upper() -- returns upper focus distance in mm, but note 'accuracy' is 1cm from Canon
    local  x=-1
    if (bi.platform=="m3") and (bi.platsub=="101a") then
      x=peek(0x00244916, 2)
    elseif (bi.platform=="m3") and (bi.platsub=="120f") then
      x=peek(0x0024495A, 2)
    elseif (bi.platform=="m3") and (bi.platsub=="121a") then
      x=peek(0x0024495A, 2)
    elseif (bi.platform=="m10") then -- same address in 110d, 110f, 110g
      x=peek(0x00272016, 2)
    elseif (bi.platform=="m100") and (bi.platsub=="100a") then
      x=peek(0x001FC7FA, 2)
    else
      print('Wrong platform')
    end
    if x == -1 then return -1 else return x*10 end
end

function lens_name() -- does what it says
    local pname = 0
    if (bi.platform=="m3") then
        if (bi.platsub == "101a") then 
            pname = 0x00244969 
        else
            pname = 0x002449ad 
        end
    elseif (bi.platform=="m10") then
        pname = 0x272065 
    elseif (bi.platform=="m100") and (bi.platsub == "100a") then
        pname = 0x1FC84E 
    end
    local len = peek(pname-1,1)
    local i = 0
    local t = {}
    while i < len do
        local c = peek(pname + i, 1)
        if c == 0 then break end
        table.insert(t, string.char(c))
        i = i + 1
    end
    local name = table.concat(t)
    return name
end

function lens_cal() -- called at the start and when focal length changes: sets lens to MFD
    call_event_proc('InitializeAdjustmentSystem')
    temp = call_event_proc('GetEFLensFocusPositionWithLensCom')
    repeat
        temp = call_event_proc('GetEFLensFocusPositionWithLensCom')
        call_event_proc("EFLensCom.FocusSearchFar")
        sleep(20)
    until temp == call_event_proc('GetEFLensFocusPositionWithLensCom') -- make sure we are at 'infinity'

    repeat -- to find some useful data
        call_event_proc("EFLensCom.MoveFocus", -1, 1)
        sleep(20)
    until get_focus_distance_lower() < 81000
    xc = get_focus_distance_lower() -- Canon lower focus distance 'infinity' start
    sleep(20)
    far_count = call_event_proc('GetEFLensFocusPositionWithLensCom')
    print("far count:"..far_count)
    temp = call_event_proc('GetEFLensFocusPositionWithLensCom')
    repeat
        temp = call_event_proc('GetEFLensFocusPositionWithLensCom')
        call_event_proc("EFLensCom.FocusSearchNear")
        sleep(10)
    until temp == call_event_proc('GetEFLensFocusPositionWithLensCom') -- make sure we are at MFD
    near_count = call_event_proc('GetEFLensFocusPositionWithLensCom')
    MFD = fmath.new(get_focus_distance_lower(),1)
    k = (MFD*(MFD-4*F)):sqrt()
    total_count = far_count - near_count -- lens max number of steps at the current focal length
    reset_lens = false
    print("FL = "..F:int())
    print("Total count = "..total_count)

    -- Use the following to log focus against counts
    if log == 1 then
        print_screen(1)
        print("--")
        print("FL= "..F:int().."mm")
        print("Stepper Motor Counts")
        for j = 1, total_count do 
            print(j)
        end
        print("TLFF distances (mm)")
        for j = 1, total_count do 
            x = TL_focus_pos(j)
            print(x:int())
        end
        print("--")
        print_screen(0)
    end
end

function TL_focus_pos(nn) -- functioalised estimate of focus from the stepper motor position
    local a = fmath.new(get_focus_distance_lower(),1)
    local b = fmath.new(get_focus_distance_upper(),1)
    local c = ((2*a*b)/(a+b)):int()
    local d = MFD
    -- use a, b or c to 'scale'' the basic functional form
    return (total_count*MFD - 2*F*nn)/(total_count-nn) - (a*nn)/(total_count)
end

function set_up()
    dof = get_dofinfo()
    F = fmath.new(dof.focal_length,1000) -- focal length in mm (real) 
end

function lens_info()
    if lens_name() == "EF-M11-22mm f/4-5.6 IS STM" then -- calculate lens thickness from manufacturer's data
        return true
    elseif lens_name() == "EF-M28mm f/3.5 MACRO IS STM" then
        return true
    elseif lens_name() == "EF-M55-200mm f/4.5-6.3 IS STM" then
        return true
    elseif lens_name() == "EF-M18-55mm f/3.5-5.6 IS STM" then
        return true
    elseif lens_name() == "EF-M15-45mm f/3.5-6.3 IS STM" then
        return true
    else -- lens not recognised
        return false
    end
end

function check_focus()
    dof = get_dofinfo()
    dirty = false
    local test_count = call_event_proc('GetEFLensFocusPositionWithLensCom')
    local test_n = fmath.new(av96_to_aperture(get_user_av96()),1000)
    local test_F = fmath.new(dof.focal_length,1000) 
    if test_F ~= F then -- recalibrate lens and update focus position
        dirty = true
        reset_lens = true
    elseif test_count ~= focus_count then -- update focus position
        dirty = true
    end
    F = test_F
    focus_count = test_count
end

function update() -- update focus position estimate in the console
    count = call_event_proc('GetEFLensFocusPositionWithLensCom') - near_count
    x = TL_focus_pos(count)
    if x:int() < INF and count <= total_count then
        print(units(x)..",Lower = "..get_focus_distance_lower()..",Upper = "..get_focus_distance_upper()..",count = "..count)
    else
      print("oo")
    end
end

-- Main Section --

if lens_info() == false then -- then don't use
    print("Can't use for now")
    sleep(3000)
    return
end

call_event_proc('FA.Create') -- assume only need to call this once
sleep(100)
set_up()
lens_cal()

finish = false

repeat -- stay here
    check_focus()
    if reset_lens then lens_cal() end -- focal length changed so recalibrate lens
    if screen_needs_refresh() then dirty = true end
    if dirty then update() end
    sleep(100) -- adjust a required
until finish  -- exit via pressing ALT exit button