Hi,
i'm from germany.
My motives are mushrooms or insects. I use zoom and lenses to reach distance and enlargement. Someone i want to use stacking pictures.

The first picture of the graph paper is scaled, the second one a cutting of the full resolution.

telescope lens :
- possible distance with sharp picture of motive 170-210mm
- max. Enlargement 60x

telescope lens + microscope lens:
- possible distance with sharp picture of motive 65-70mm
- max. Enlargement 145x

telescope lens + 2 microscope lenses :
- possible distance with sharp picture of motive ~10mm
- max. Enlargement 220x

I want to use Depth of Field Calculator for calculate necessary next focus. There are my problems.
With ~10x zoom (growing). I get mistakes. get_dof is negative but why? Why dof becomes smaler, it shoot become bigger.

get_dof.lua -- manual i change the focus (bigger as 10x)and start the script

--[[ 
@title get_dof-LUA
]] 

print_screen (100*get_time("m")+get_time("s")) 

sleep (3000) 

    d = get_focus ()
    e = get_dof ()
    g = get_focus ()
    h = get_hyp_dist ()
    print ( "get_focus " .. d ..  " get_dof " .. e  .. " get_focus " .. g .. " get_hyp_dist " .. h )

sleep (500)

get_dof (sx200is-100d-0.9.9-1042-full.zip)

get_focus 1081 get_dof 52 get_hyp_dist 45556
get_focus 1076 get_dof 35 get_hyp_dist 65469
get_focus 1077 get_dof 31 get_hyp_dist 75370
get_focus 1078 get_dof -1 get_hyp_dist -63573
get_focus 1078 get_dof -1 get_hyp_dist -58967
get_focus 1078 get_dof -1 get_hyp_dist -25691

get_dofinfo.lua

--[[

@title get_dofinfo-LUA

@param s steps 20

@default s 20

]]



print_screen (100*get_time("m")+get_time("s")) 


sleep (3000)

f = get_focus ()

print ( "get_focus: " ..  f) 




for i=1,s do

    d = get_dofinfo()

   sleep (500)

    print("d.focus: " .. d.focus .. " d.aperture: " .. d.aperture .. " d.dof: " .. d.dof .. " focal_length:" .. d.focal_length ) 

   sleep (500)

    h = d.focus+d.dof/2

   sleep (500)

   set_focus (h)

   sleep (500)
end

get_dofinfo (sx200is-100d-1.1.0-full_rev_552.zip de)

get_focus: 14756
d.focus: 14756 d.aperture: 5657 d.dof: 13148 focal_length:33066
d.focus: 14756 d.aperture: 5657 d.dof: 13148 focal_length:33066
d.focus: 14756 d.aperture: 5657 d.dof: 13148 focal_length:33066
d.focus: 14756 d.aperture: 5657 d.dof: 13148 focal_length:33066
d.focus: 14756 d.aperture: 5657 d.dof: 13148 focal_length:33066
d.focus: 14756 d.aperture: 5657 d.dof: 13148 focal_length:33066
d.focus: 14756 d.aperture: 5657 d.dof: 13148 focal_length:33066
d.focus: 14756 d.aperture: 5657 d.dof: 13148 focal_length:33066
d.focus: -1 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: -1 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: -1 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: -1 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: -1 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: -1 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: 30397 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: 30397 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: 30397 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: 30397 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: 30397 d.aperture: 5657 d.dof: -1 focal_length:33066
d.focus: -1 d.aperture: 5657 d.dof: -1 focal_length:33066

By hand it functions, but it is not the best way.

fokus-stacking.lua

--[[
@title Fokus-Stacking-LUA
@param a Fokus-Schritte [10] +
@default a 10
@param b Schrittweite [10]
@default b 10
@param d Anstieg [3]
@default d 31
@param h Ruhepause [3000]
@default h 3000
]]

print_screen (100*get_time("m")+get_time("s"))                        

if a<1 then a=10 end
if b<1 then b=10 end
if d<1 then d=3 end
if h<1 then h=3000 end


sleep (h)
f = get_focus ()

for i=1,a do
--  g=f+(d*(i^5)/(m*10^5)+i)*10*b
-- d größer -> kleinerer Anstieg
-- b vielfaches der Schrittweite
    m = math.pow(10,5)/5
    l = math.pow(i,5)
    k = 10*l/(d*m)+i
    g = f+k*b
    sleep (500)
if g<54670 then
    set_focus (g)
      shoot ()
    print ( "Foto: ".. i .. " Fokus: " .. g )
else
    print ( "max. Fokus" )
    sleep (3000)

end
end

set_focus (f)

Can someone find a solution?

bye,
Nando