As some may have been following in my previous posts, I’ve been trying to write a Lua script to help with both focus and exposure bracketing in my Magic Lantern enhanced Canon. My goal remains to write an automatic script for this, ie one button push: but until the Lua and ML coding gets ‘fixed’, I’ve decided to settle on a manual-based ‘helper script’.
At first, I thought I could achieve more than I have, but even the might of the ML gurus (David Milligan et al) could not ‘educate’ me enough to sort out the ‘complexities’ of semaphore errors :-)
I thus offer the following as a user-driven, ‘workflow helper script’. It is aimed at those that are interested in landscape (sic) focus AND exposure bracketing, ie together.
The script assumes your lens reports position and depth of field and is in Live View. You, obviously, must have the Lua module loaded.
In addition, the user needs to ensure that ML ETTR is switch on (I prefer to trigger from the SET button) and that ML exposure settings preference is set, eg 3 x 2Ev. The script provides the option to switch bracketing from current exposure, ie symmetrically about the current exposure, or, following an ETTR SET exposure, from the ETTR. The script switches to the correct sequence, according to if ETTR is used or not.
In addition the script provides a convenient way to take a ‘bookend’ exposure, ie a dark frame, which is toggled on and off via the RATE button (the user can change the button in the script). This also handles exposure bracketing to allow a single frame capture, even if you are doing exposure bracketing (see below).
The workflow that I use with this script goes like this:
Setup Phase
1. Ensure ML-ETTR enabled (I personally use the SET button). Also select diffraction aware in the ML DoF menu, and switch DoF on;
2. Ensure the number of frames (Auto or a number) and Ev delta is set in the ML-Bracketing menu. Note bracketing doesn’t need to be switched on at this stage;
3. Go the the Landscape Stacking Helper (by default positioned in the Audio ML Menu, but this can be changed in the script);
4. Select the Exposure bracketing strategy you need, ie ‘None’, symmetrically ‘From here’ or ‘From ETTR’ exposure;
5. Select the bracket to bracket focus overlap. This is an additional helper feature that attempts to show you are x% overlapping, but note, according to the lens it doesn’t always show/work;
6. Select if you wish to use image ‘bookends’, which will allow you to quickly take a dark frame or two dark frames to help differentiate between various bracket sets;
7. Finally, in the script menu, turn on the script and do a half shutter press to get rid of the menu or go to LV to remove the script’s menu;
Use Case 1 - Simple Focus Bracketing (without bookends)
1. Switch on Live View, compose, set exposure and focus on the nearest point in your focus stack;
2. Press shutter (eg with your choice of delay etc in the normal Canon menu, or use a remote) and grab the first image;
3. In the top right of the ML top bar you will see a yellow rectangle, indicating the next bracket needs to be moved towards infinity;
4. Rotate the lens (or use ML Follow Focus) to move the lens towards infinity until the yellow box turns Green or Red;
5. If it turns Green this indicates you are in the % overlap region. If it turns red this means you have negative overlap, ie a focus gap, and you should move the lens towards the macro end until it goes green or just yellow. According to the lens, focus point or aperture settings, you may not see green;
6. Press the shutter and grab the next image;
7. Repeat the above until Inf (infinity) is seen in the coloured box (consider taking an insurance image beyond this point if you wish, ie focus point actually at or near infinity;
8. To start another bracket set, simply move the lens to the closest object and take the first image to reset the helper and repeat as above.
Use Case 2 - Simple Focus Bracketing (with bookends)
1. The ‘problem’ with the above (simple) workflow is that if subsequent bracket sets are similar, ie no change in composition, you may have problems in post differentiating the bracket sets (unless you remember how many images in each set. For this reason I have included a simple ‘bookend’ tool;
2. To use the bookend tool, ensure it is switched on, in the helper menu;
3. At the start of the focus bracketing, simple press the RATE button (unless you have changed this in the script). The LV image will go black. Press the shutter, to grab this dark ‘bookend’ image, and then press RATE again, to toggle back to the correct/original exposure;
4. Carry on as in Use Case 2 until the final focus bracket is reached;
5. Press RATE to switch to dark frame mode, grab a final bookend image, and press RATE to reset the exposure. You now have a focus set bookended by dark frames, thus allowing you to easily differentiate this set in post processing.
Use Case 3 - Focus and Exposure Bracketing (with bookends)
1. Ensure bookends are enabled and that the required exposure bracketing strategy has been set up in the ML menu (let’s assume we are going to take three brackets from an initial ETTR exposure);
2. Press SET to set the ETTR base exposure;
3. Focus on the closest focus point;
4. Press RATE and take two (sic) dark frames (as we will need to differentiate an exposure bracket set within a focus bracket set. This become especially important if you decide to use Auto bracketing, where the exposure bracket may change between different focus sets. Also note that if using auto bracketing, you will need to give a half-shutter press to clear the auto bracketing screen feedback - I have put in a feature request to ‘fix this’, ie return the screen after an auto bracketing capture);
5. Press RATE to return to the ETTR base exposure;
6. Press the shutter (or remote) to take the first exposure bracket set at the first focus bracket point;
7. Press RATE, Press the shutter/remote and Press RATE to bookend the first focus set;
8. Move the lens to the next focus point using the colour indicator;
9. Press RATE, Press shutter and Press RATE to bookend the start of the next focus/exposure set;
10. Press the shutter/remote to take the exposure bracket set at the this focus bracket point;
11. Keep doing the above until Infinity reached (consider grabbing an insurance focus/exposure set with the focus point at or near infinity (note the infinity warning is when Depth of Field Far reaches infinity);
12. Finally, press RATE, Press shutter twice (sic) and Press RATE to bookend the entire set. You will now have a set of images on your card with a pattern like this:
Dark
Dark
Focus1/Exposure1
Focus1/Exposure2
Focus1/Exposure3
Dark
Focus2/Exposure1
Focus2/Exposure2
Focus2/Exposure3
Dark
Dark
Finally, the usual caveats: you use the script at your own risk. I have tested it with my 5D3 and a 24-105 F/4L lens; and I welcome feedback regarding making the script better.
For those that wish to explore, here is the script (UPDATED 13-March-16):
--[[
Manual Landscape bracketing helper script
Version 0.3.6
Garry George Feb 2016
http://photography.grayheron.net/
Workflow helper script for focus and exposure bracketing.
Try using ML follow focus to control the lens, as opposed to rotating lens by hand.
Yellow means move more towards the infinity end, Red means move more towards macro end,
Green means at the sweet spot. If Green not seen, move to just being in the Yellow from being in the Red.
************************
* Must be in liveview! *
************************
--]]
a1 = lens.dof_near
b1 = lens.dof_far
c1 = 0
fp = lens.focal_distance
inf = 1000000
started = false
bookended = true
current_tv = camera.shutter.ms
factor = .2
event.keypress = function(key)
if keymenu.submenu["Turn On/Off"].value == "Off" then
started = false
return true
else
if key == KEY.RATE then
if keymenu.submenu["Bookends"].value == "yes"
then
if bookended then
current_tv = camera.shutter.ms
camera.shutter.ms = 1
if keymenu.submenu["Exposure bracketing"].value ~= "None" then i = menu.set("Shoot","Advanced Bracket",0) end
bookended = false
else
camera.shutter.ms = current_tv
if keymenu.submenu["Exposure bracketing"].value ~= "None" then i = menu.set("Shoot","Advanced Bracket",1) end
bookended = true
end
return false
else
return true
end
end
if key == KEY.FULLSHUTTER
then
b1 = lens.dof_far -- in mm
fp = lens.focal_distance -- in cm
c1 = b1 - (b1 - fp*10)*factor
started = true
return true
end
end
end
lv.info
{
name = "Landscape Stacker Info",
value = "",
priority = 100,
update = function(this)
this.value = ""
if fp == 0 then
this.value = ""
else
if keymenu.submenu["Turn On/Off"].value == "On"
then
if started then
a2 = lens.dof_near
this.value = ""
if a2 > b1 then
this.background = COLOR.RED
elseif a2 < c1 then
this.background = COLOR.YELLOW
this.foreground = COLOR.BLACK
else
this.background = COLOR.GREEN1
end
if lens.dof_far >= inf then
this.value = "Inf"
else
this.value = " "
end
end
else
this.value = ""
end
end
end
}
keymenu = menu.new
{
parent = "Audio",
name = "Landscape Stacking Helper",
help = "First focus at nearest point in bracket set",
help2 = "and take first picture",
depends_on = DEPENDS_ON.LIVEVIEW,
submenu =
{
{
name = "Turn On/Off",
help = "Switches the script on/off",
help2 = "Simply enables addition button functionality",
depends_on = DEPENDS_ON.LIVEVIEW,
choices = {"Off","On"},
},
{
name = "Bracket to bracket overlap",
help = "Amount to overlap each bracket",
help2 = "% of FP-2-DoF(far) distance",
choices = {"20","10", "5"},
update = function(this)
factor = tonumber(keymenu.submenu["Bracket to bracket overlap"].value)/100
end,
},
{
name = "Bookends",
help = "Toggles a dark frame exposure",
choices = {"no","yes"},
},
{
name = "Exposure bracketing",
help = "Set options in the ML bracketing menu",
choices = {"None","From here", "From ETTR"},
update = function(this)
if keymenu.submenu["Exposure bracketing"].value == "None" then
i = menu.set("Shoot","Advanced Bracket",0)
else
i = menu.set("Shoot","Advanced Bracket",1)
if keymenu.submenu["Exposure bracketing"].value == "From ETTR" then i = menu.set("Advanced Bracket","Sequence",2) end
if keymenu.submenu["Exposure bracketing"].value == "From here" then i = menu.set("Advanced Bracket","Sequence",1) end
end
end
}
}
}
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