Landscape Focus Bracketing Script
- Written for/on: G7X and G1X
- Also works on: Should work on any camera that runs CHDK
- Required CHDK build: Anything recent as of 2018
Latest version of script may be downloaded from: https://gist.github.com/pigeonhill/10a43f5ba543bc758f1ce21d28981a89
Notes & Usage Unlike macro focus bracketing, where the focus step is the same each time and very small; in landscape focus bracketing we need to calculate the focus for each step. To get the full benefits from this script, it is useful to remember that, ignoring diffraction, at the near and far depth of fields the defocus blur is, by definition, the so-called Circle of Confusion. This blur is usually accepted as being 30 microns for a 35mm full frame camera, and scaled by the crop factor for other formats, eg 11 microns on the G7X.
Having said this, 30 microns, is not the 'best focus' quality but you will not see the differences on your Facebook images, only when you create high (focus) quality prints that will be scrutinised close up, eg in a competition. As you need a line pair (black and white pixels, to see a line, it is not sensible to consider CoCs less than, say, 2 sensor pixels.
Defocus blur is, of course, zero at the point of focus. Also, at the Hyperfocal distance (H), the blur at infinity will be the CoC. It is useful to note that any blur at infinity can be 'dialed in', by simply focusing at a distance either side of H. Thus, on my G7X, with a CoC of 11 microns, if I focus at twice H, then the infinity blur will be CoC/2. Likewise, at H/4, the infinity blur will be 4*CoC.
The script scales everything relative to H and the following chart illustrates how defocus blur varies with respect to H. Note the chart shows an estimate of the near and far DoFs that can be used in your head: the script uses a more ‘accurate’ estimate.
When focus bracketing we must at least ensure the previous image's far DoF is the same as the next image's near DoF: assuming we are focusing near to far as we are in this script. However, many wish to introduce some 'insurance' and have an overlap between the focus brackets. The script provides four options for this overlap: none, 2*CoC/3, CoC/2 and diffraction aware.
With diffraction aware overlap, the script calculates the infinity defocus blur to use, that ensures that the defocus blur and diffraction blur, taken together in quadrature, are equal to the CHDK CoC. This overlap blur criterion will never be less than the CHDK set CoC/3.
The following illustrates the overlap between image n and n+1. Note that using the overlap feature comes at the cost of needing to take more brackets
Having achieved the perfect focus brackets, the script will then create an additional bracket beyond H, ie to cover the infinity focus quality. The options being 2H, 3H or 4H, giving infinity blurs of CoC/2, CoC/3 or CoC/4. If diffraction aware is being used for the overlap, the last image will be around CoC/3.
By default the script creates a dark image at the beginning and end of the focus bracket set, to help differentiate the sequence in post. You can turn this off via the menu.
At each focus point you can also ask the script to create two additional exposure brackets at either -xEv & +xEv, -xEv & --xEv or at +xEv and ++xEv. X can be 1 or 2Ev from the base exposure. These options cover all the usual exposure bracketing options, eg if in Av mode it would be usual to choose the -/+ logic. If using M mode and following an ETTR approach, then a +/++ logic would be the best choice.
In addition to the 'normal' bracketing option, the script offers two additional schemes. First, an ISO-less bracketing option (ISO 800 or ISO 1600) that assumes (sic) the camera is ISO-less above ISO 800 or 1600 (check your camera to ensure you select the right ISO so the sensor read noise swamps the banding). Thus there is no point in taking brackets in the camera above this, ie just push in post. The ISO option is good for hand-holding situations and the script assumes your base ISO is 100.
As an illustration, the chart on the right, from the DXOMark site, shows the G1X vs G7X. As can be seen the G7X can be assumed to be fully ISO invariant, which means doing ISO bracketing is pointless, ie simply push a single base exposure in post (as long as you are not too underexposed ;-))
On the other hand the G1X is only ISO-less above about 1600. Hence take a single additional bracket at, say, ISO1600.
The second additional scheme makes use of the 'Zero-Noise' approach, as suggested by Guillermo Lujik. In this mode a second time bracket is taken at +4Ev from the first one. To use the ZN option, simply ETTR to capture the highlights and the script will create a +4Ev additional image for the shadow areas.
Because focus bracketing can create large sequences, the script will warn you if the requested bracket sequence is more than your maximum number, which is set to 10 focus steps, but this can be changed as you wish in the script. Note that 10 focus steps will result in 30 images if you have exposure bracketing switched on.
In macro mode, eg using Macro2X or X2DelX, the script will take as many images as required, ie without warning how many!
In order to cover various needs, the user can select from the following focusing scenarios:
- From the current focus to the blur-defined Infinity
- From the minimum focus to the current focus
- From current focus to a specified number of mm beyonds
- From the minimum focus to the blur-defined Infinity
Finally, the script will create a log file #2306, where the focus positions (mm) for each image will be recorded. You can delete this file from within the script. The default is no log file.
To use the script, simply focus on the nearest point of interest and place the camera in manual focus mode. On the G7X you seem to need to do at least one focus operation to get CHDK to set the correct H, thus it is good practice to ensure H is stable, ie by looking at the CHDK DoF feedback. That is constant, for the aperture and focal length you are at, irrespective of focus.
The script is started in the normal way, eg by doing a shutter press.
Here is a test image where I focused on our cat's mouse, at about a foot away from the camera, and used diffraction aware overlap. The script took 7 perfectly abutted F/4 focus images, accounting for diffraction, and two additional exposure brackets at each focus station, ie 21 images. The post processing was carried out in Lightroom, with a round trip to Helicon Focus.
The second example is using the macro mode, ie X2DelX here.
Finally, you will find information about this script and other photography matters on my blog at photography.grayheron.net
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Script Code Save to your /SCRIPTS/ folder as usual. Note the following may not be the latest version, which is always available at:
☀https://gist.github.com/pigeonhill/10a43f5ba543bc758f1ce21d28981a89
--[[
@title Landscape Bracketing
'Perfect' focus brackets from near to blur defined 'infinity': overlap defined at a fraction of camera's CoC
Plus option of two additional exposure brackets at each focus step, at 1Ev, 2Ev or 3Ev using -/+ or -/-- or +/++ logic
More info at https://chdk.wikia.com/wiki/Landscape_Focus_Bracketing_:_perfect_near_to_far_focus_brackets
Camera should be in manual focus mode and M mode
Release 1.9981
Tested on a G7X & G1X
(c) Garry George
@chdk_version 1.5
@param u Focus stack mode?
@default u 0
@values u X2Inf Mac2Inf Mac2X X2delX
@param g Overlap at?
@default g 3
@values g CoC 2CoC/3 CoC/2 diff
@param p Exposure bracket delta?
@default p 0
@values p None 1Ev 2Ev 3Ev 800 1600 ZN
@param j Exposure bracket logic?
@default j 0
@values j 0/-/+ 0/-/-- 0/+/++
@param m Delta from X (mm)
@default m 25
@range m 1 200
@param n Max number of focus brackets?
@default n 10
@range n 4 30
@param c Script Delay (s)
@default c 3
@range c 0 5
@param b Bookends?
@default b 1
@values b No Yes
@param q Infinity focus quality?
@default q 1
@values q CoC/2 CoC/3 CoC/4
@param v Show bracket pos?
@default v 1
@values v No Yes
@param k Log?
@default k 0
@values k No Yes
@param e Delete Log File?
@default e 0
@values e No Yes
--]]
capmode = require("capmode")
if (capmode.get_name() ~= "M") then
print("Switch to M mode")
return -- exit script
end
if get_focus_mode() ~= 1 then
print("Switch to MF mode")
return -- exit script
end
if e == 1 then
local fp = io.open("A/CHDK/DATA/LBS.CFG")
local str = fp:read("*all")
fp:close()
temp = string.sub(str, 1, 1)
temp = "A/CHDK/DATA/LBS."..temp
fp = io.open (temp,"r")
if fp == nil then
print("No ConFig file found")
return
else
str = fp:read("*all")
fp:close()
if string.find(str,"e=0") == nil then
str = string.gsub(str,"#e=1","#e=0")
fp = io.open (temp,"w")
fp:write(str)
fp:close()
os.remove("A/CHDK/LOGS/LOG_2306.TXT")
print("Log File Deleted")
return -- exit script
end
end
end
press("shoot_half") -- get current exposure
t = get_tick_count()
repeat
sleep(50)
if get_tick_count() - t > 5000 then
print("Unknown Error")
release("shoot_half")
return
end
until (get_shooting() == true)
release("shoot_half")
s = get_tv96()
av = get_av96()
if (get_focus() == -1) then
print("@ Infinity")
return -- exit script
end
dof = get_dofinfo()
x = dof.focus
x_start = x
last_x = x
if u == 1 or u == 2 then -- change focus to min focus
set_focus(10)
press("shoot_half")
repeat
x = get_focus()
sleep(100) -- seems to work on G7X & G1X, may need changing on other cams
until x == get_focus()
release("shoot_half")
end
base_h = dof.hyp_dist
temp = 0
temp1 = 0
temp2 = 0
ok = true
fl = dof.focal_length/100
log = {}
count = 0
-- A few Functions
function bookend()
if b == 1 then
set_tv96(960)
set_av96(640)
shoot()
set_tv96_direct(s)
set_av96_direct(av)
end
end
function refocus(xx)
local dis = 0
set_focus(xx)
press("shoot_half")
repeat
dis = get_focus()
sleep(200) -- seems to work on G7X & G1X, may need changing on other cams
until dis == get_focus()
sleep(500)
release("shoot_half")
end
function X_bracket()
set_tv96_direct(s)
count = count + 1
if p == 0 then
shoot()
elseif p < 4 and j == 0 then
shoot()
set_tv96_direct(s-96*p)
shoot()
set_tv96_direct(s+96*p)
shoot()
elseif p < 4 and j == 1 then
shoot()
set_tv96_direct(s+96*p)
shoot()
set_tv96_direct(s+2*96*p)
shoot()
elseif p < 4 and j == 2 then
shoot()
set_tv96_direct(s-96*p)
shoot()
set_tv96_direct(s-2*96*p)
shoot()
elseif p == 4 then
local iso = get_sv96()
set_sv96(sv96_market_to_real(iso_to_sv96(100)))
shoot()
set_sv96(sv96_market_to_real(iso_to_sv96(800)))
shoot()
set_sv96(iso)
elseif p == 5 then
local iso = get_sv96()
set_sv96(sv96_market_to_real(iso_to_sv96(100)))
shoot()
set_sv96(sv96_market_to_real(iso_to_sv96(1600)))
shoot()
set_sv96(iso)
elseif p == 6 then
shoot()
set_tv96_direct(s-96*4)
shoot()
end
set_tv96_direct(s)
end
h = base_h -- no overlap case: brackets 'touch' at CHDK CoC
if g == 1 then -- adjust h to achieve the requested overlap, ie 'touching' at 2*CoC/3 or CoC/2 or at the diffraction aware defocus blur
h = (h*3)/2
elseif g == 2 then
h = 2*h
elseif g == 3 then -- use diffraction aware overlap: Assume CHDK CoC is total blur, formed in quadrature from defocus and diffraction blurs
temp1 = 1000*dof.coc -- total blur set up for imath
temp2 = (1342*dof.aperture)/1000 -- set up for imath. From diff_blur = 2.44*0.55*N (um)
if temp1 > temp2 then -- can use diffraction aware overlap
temp = imath.sqrt(imath.mul(temp1,temp1) - imath.mul(temp2,temp2)) -- diffraction aware defocus blur
temp2 = imath.div(temp1,temp)
if temp2 > 3000 then
h = 3*h
print("Warning: High Diff: using CoC/3")
else
h = (h*temp2)/1000
end
else -- diff blur > total blur
h = 3*h
print("Warning: Diff>Defocus: using CoC/3")
end
end
if u == 2 or u == 3 then
dof = get_dofinfo()
x = dof.focus -- register actual x
last_x = x
sleep(c*1000)
bookend()
if u == 3 then x_start = x_start+m end
repeat -- to capture focus brackets from min focus up to x
X_bracket()
temp = get_exp_count().." @ "..x.."mm"
if v == 1 then print(temp) end
x = (x*(h*10 - 2*fl))/(h*10 - 2*x*10) -- position of next focus bracket
if (x - last_x) == 0 then x = last_x + 1 end
if x < last_x or x == -1 then
print("Unknown Error")
refocus(x_start)
return
end
refocus(x) -- request move to x
dof = get_dofinfo()
x = dof.focus -- register actual x moved by cam
last_x = x
until ((x <= 0) or (x > x_start))
refocus(x_start)
dof = get_dofinfo()
x = dof.focus -- register actual x moved by cam
X_bracket()
bookend()
temp = get_exp_count().." @ "..x.."mm"
if v == 1 then print(temp) end
sleep(1000)
return -- exit script
end
if (x > base_h or x == -1) then
print("@/beyond H")
sleep(c*1000)
X_bracket()
temp = get_exp_count().." @ "..x_start.."mm"
if v == 1 then print(temp) end
sleep(1000)
return -- exit script
else
num = ((10*(h + x))/(2*x) + 5)/10
end
if num > n-1 then -- accounting for last bracket at infinity focus
print("Warning")
temp2 = num + 1
print("^ max # brackets to "..temp2)
return -- exit script
end
sleep(c*1000)
bookend()
refocus(x_start) -- explicitly refocus to start
dof = get_dofinfo()
x = dof.focus
last_x = x
if k == 1 then log[#log + 1] = "\n"..os.date() end
X_bracket()
temp = get_exp_count().." @ "..x.."mm"
if v == 1 then print(temp) end
if k == 1 then log[#log + 1] = temp end
repeat -- to capture focus brackets up to just past h/3
x = (x*(h*10 - 2*fl))/(h*10 - 2*x*10) -- position of next focus bracket
if x <= last_x or x == -1 then
print("Unknown Error")
refocus(x_start)
return
end
refocus(x) -- request move to x
dof = get_dofinfo()
x = dof.focus -- register actual x moved by cam
last_x = x
X_bracket()
temp = get_exp_count().." @ "..x.."mm"
if v == 1 then print(temp) end
if k == 1 then log[#log + 1] = temp end
until ((x <= 0) or (x > h/3))
temp1 = h
temp2 = base_h*(q+2)
refocus(temp1) -- take shot at h
X_bracket()
temp = get_exp_count().." @ "..temp1.."mm"
if v == 1 then print(temp) end
if k == 1 then log[#log + 1] = temp end
if temp2 > temp1 then -- take additional infinity focus shot
refocus(temp2)
X_bracket()
temp = get_exp_count().." @ "..temp2.."mm"
if v == 1 then print(temp) end
if k == 1 then log[#log + 1] = temp end
end
bookend()
temp = count.." focus brackets"
print(temp)
if k == 1 then log[#log + 1] = temp end
temp1 = ((10*dof.coc*base_h)/temp2 + 5)/10
temp = "Infinity blur "..temp1.."um"
if k == 1 then log[#log + 1] = temp end
if p ~= 0 and k == 1 then log[#log + 1] = "Exposure offset = "..p.."Ev" end
refocus(x_start)
if k == 1 then
print_screen(-2306)
for i = 1, #log do
print(log[i].."\n")
end
end