Bulb_ND.lua

--[[ 
Bulb ND Script V1
Release 0.1
Jan 2017

Simply takes an ND image using the currently set shutter value, but assumes an ND filter is fitted.
To use:
1. Compose and set shutter WITHOUT the ND filter fitted
2. Set ND values in menu and delay (in LV delay is automatically 3s)
3. Press SET to intiate script
4. Fit ND filter
5. Run script by doing a half shutter press

Pushing any button, other than the halfshutter, clears the script, ie you will need to renter the menu to rerun

*******************************************************************************************************
*																				  				  *
* If you reference this script, please consider acknowledging me at http://photography.grayheron.net/ *
*																				  				  *
*******************************************************************************************************
--]]

temp = 0
ND_shutter = 0

function my_shoot()
	if ND_shutter > 30 then
		camera.bulb(ND_shutter)
	else 
		camera.shutter.ms = ND_shutter*1000
		camera.shoot(false) -- Note may need to change to camera.shoot(64,false) on some Lua builds
	end
end

function run_script()
	menu.close()  -- just in case
    local save_current_shutter = camera.shutter.apex
	ND_shutter = camera.shutter.apex - scriptmenu.submenu["ND Full Stop Value?"].value - scriptmenu.submenu["ND Fractional value?"].value/10
	msleep(scriptmenu.submenu["Delay?"].value * 1000)
	ND_shutter = 2^(-ND_shutter) -- convert to seconds
    my_shoot()
	camera.shutter.apex = save_current_shutter -- reset to non ND shutter value
end

function mytest(key)
	if key == KEY.HALFSHUTTER then
		run_script()
		event.keypress = nil
		return false
	else
		event.keypress = nil
		return true
	end
end

function start()
	menu.close()  -- just in case
	if  scriptmenu.submenu["ND Full Stop Value?"].value ~= 0 then
		event.keypress = mytest -- set up keypress handler
	end
end

scriptmenu = menu.new
{
    parent = "Shoot", -- change this to position the script into other ML menu locations
    name = "Bulb ND",
    help = "Set shutter without ND fitted",
    submenu =
	{
		{
			name = "Run Script",
			select = function(this) 
			if key.last == KEY.SET then task.create(start) end
			end,
			help = "Runs the main script after pressing SET",
			help2 = "Now fit ND and press halfshutter",
		},
		{
			name = "ND Full Stop Value?",
			help = "In stops",
			min = 0,
			max = 16,
			value = 0,
			warning = function(this)
			temp = camera.shutter.apex - scriptmenu.submenu["ND Full Stop Value?"].value - scriptmenu.submenu["ND Fractional value?"].value/10
			temp = math.ceil((2^(-temp))*1000)/1000
			if temp > 30 then temp = math.ceil(temp) end
			return "ND Shutter (s): ".. tostring(temp)
			end,
		},
		{
			name = "ND Fractional value?",
			help = "In tenths",
			min = 0,
			max = 9,
			value = 0,
			warning = function(this)
			temp = camera.shutter.apex - scriptmenu.submenu["ND Full Stop Value?"].value - scriptmenu.submenu["ND Fractional value?"].value/10
			temp = math.floor((2^(-temp))*1000)/1000
			if temp > 30 then temp = math.floor(temp) end
			return "ND Shutter (s): ".. tostring(temp)
			end,
		},
		{
			name = "Delay?",
			help = "In seconds",
			min = 0,
			max = 5,
			value = 0,
		}
	}
}