Nuke node to automate the blending of multiple bracketed exposures into a single high dynamic range hdr image. Includes a script to sort the input nodes based on exposure time.

README.md

ExposureBlend

ExposureBlend is a Nuke node to automate the blending of multiple bracketed exposures into a single high dynamic range hdr image.

A sort function is included, which can analyze hundreds of input images and parse them out into groups of bracketed exposure sets. The sort function depends on the Exif:DateTimeOriginal metadata key being present in order to detect bracket sets.

Full credit goes to Santi Svirsky for the technique.

Have fun!

ExposureBlend.nk

set cut_paste_input [stack 0]
push $cut_paste_input
Group {
 name ExposureBlend
 label "\[value brackets] Brackets"
 addUserKnob {20 ExposureBlend_tab l ExposureBlend}
 addUserKnob {7 time_th l "time threshold" t "threshold duration in seconds between exposure bracket sets" R 1 10}
 time_th 2
 addUserKnob {1 capture_time l "capture time" t "Enter the metadata key for the exposure capture time metadata key in your source images"}
 capture_time exr/Exif:DateTimeOriginal
 addUserKnob {22 sort_selected_reads l "Sort Selected Reads" t "Sort selected read nodes by exposure time, and create an ExposureBracketBlender for each exposure set.\n\n" T "from __future__ import with_statement\nimport nuke\nimport os, math\nfrom datetime import datetime\n\ndef hex_color(r, g=None, b=None):\n    # Return hex code for given rgb tuple. g and b are optional. If not specified, a greyscale value will be returned.\n    # r g and b should be between 0 and 1\n    if not g:\n        g = r\n    if not b:\n        b = r\n    return int('%02x%02x%02x%02x' % (int(r)*255,int(g)*255,int(b)*255,1), 16)\n\ndef unselect():\n    _ = \[n.setSelected(False) for n in nuke.allNodes(recurseGroups=True)]\n\ndef sort():\n    # For selected read nodes:\n    # Sort by exposure time, seperate by bracked set\n\n    grid_x = int(nuke.toNode('preferences').knob('GridWidth').value())\n    grid_y = int(nuke.toNode('preferences').knob('GridHeight').value())\n\n    node = nuke.thisNode()\n    time_th = node\['time_th'].getValue()\n\n    nuke.root().begin()\n    nodes = nuke.selectedNodes('Read')\n    if not nodes:\n        nuke.message(\"Please select a number of read nodes to sort.\")\n        return\n\n    unselect()\n    node.setSelected(True)\n    nuke.nodeCopy('%clipboard')\n    unselect()\n\n    task = nuke.ProgressTask('Sorting \{0\} Exposure Brackets'.format(len(nodes)))\n\n\n    # http://strftime.org\n    capture_time = node\['capture_time'].getValue()\n    data = \{n:(n.metadata().get('input/exposure_time'), datetime.strptime(n.metadata().get(capture_time), r'%Y:%m:%d %H:%M:%S')) for n in nodes\}\n\n    # bracket_sets is a list that will contain lists of exposure bracket sets\n    bracket_sets = \[]\n    bracket = \[]\n\n    # Loop through all images, group into exposure brackets by calculating time difference\n    data_by_time = sorted(data.items(), key=lambda x: x\[1]\[1])\n\n    for i, exposure in enumerate(data_by_time):\n        read = exposure\[0]\n        etime = exposure\[1]\[0]\n        ctime = exposure\[1]\[1]\n        task.setProgress( int( float(i) / len(data_by_time) * 100) )\n        if task.isCancelled():\n            break\n        task.setMessage('Getting next exposure time: \\t\{0\}'.format(read.name()))\n        if i < len(data_by_time)-1:\n            next_ctime = data_by_time\[i+1]\[1]\[1]\n\n        task.setMessage('Calc time diff: \\t\{0\}'.format(read.name()))\n        time_diff = next_ctime - ctime\n\n        task.setMessage('Printing info: \\t\{0\}'.format(read.name()))\n        # print(\"===> \", read.name())\n        # print(etime)\n        # print(ctime.isoformat())\n        # print(time_diff.total_seconds())\n\n        task.setMessage('Append lists: \\t\{0\}'.format(read.name()))\n        if time_diff.total_seconds() > time_th:\n            # print \"New bracket Detected!\\n------------------------------------------------------------\\n\\n\"\n            bracket.append((read, etime, ctime, time_diff.total_seconds()))\n            bracket_sets.append(bracket)\n            bracket = \[]\n        else:\n            bracket.append((read, etime, ctime, time_diff.total_seconds()))\n        # Add last images to the last exposure set\n        if i == len(data_by_time)-1:\n            bracket_sets.append(bracket)\n            bracket = \[]\n\n\n    pos = (node.xpos(), node.ypos() - grid_y*12)\n    # Loop through each exposure set, sort by exposure time dark to bright\n    # Sort horizontally\n    for i, eset in enumerate(bracket_sets):\n        if task.isCancelled():\n            break\n        esetsort = sorted(eset, key=lambda x: x\[1])\n        set_size = len(esetsort)\n        print(\"Exposure set \{0\} contains \{1\} images: \\n\\t\{2\}\".format(i, set_size, \"\\n\\t\".join(\[\"\{0\}     \\t\\t- \{1\} \\t: \{2\} \\t- \{3\}\".format(e\[0].name(), os.path.basename(e\[0]\['file'].getValue()), e\[1], e\[2]) for e in esetsort])))\n\n        task.setMessage('Sorting exposure set: \\t\{0\}'.format(i))\n        # Create new exposure blender if we have a complete exposure set\n        if set_size > 1:\n            nuke.nodePaste(\"%clipboard\")\n            new_brack = nuke.selectedNode()\n            unselect()\n            new_brack.setXYpos(pos\[0], pos\[1]+grid_y*10)\n            new_brack\['brackets'].setValue(set_size)\n            # Set base exposure to 1 up from middle frame\n            # new_brack\['exposure'].setValue(esetsort\[-2]\[1])\n            new_brack\['exposure'].setValue(esetsort\[int(math.ceil(float(set_size)/2))]\[1])\n\n        for j, e in enumerate(esetsort):\n            if task.isCancelled():\n                break\n            cur_node = e\[0]\n            etime = e\[1]\n            ctime = e\[2]\n            cur_node.setXYpos(pos\[0], pos\[1])\n            cur_node\['tile_color'].setValue(hex_color(float(j)/set_size*0.8+0.2))\n            if set_size > 1:\n                new_brack.connectInput(0, cur_node)\n\n            pos = (pos\[0] + grid_x, pos\[1])\n            # space between big exposure time diffs\n            # if e\[3] > 100:\n            #     pos = (pos\[0] + grid_x*4, pos\[1])\n\n        pos = (pos\[0] + grid_x, pos\[1])\n\n    nuke.delete(node)\nsort()" +STARTLINE}
 addUserKnob {22 ungroup l Ungroup t "Ungroup this ExposureBracketBlender so you can manipulate the graph more easily.\n\nUseful if you need to keep only pieces of certain exposures, for example if there is motion in the frame." -STARTLINE T "def unselect():\n    _ = \[n.setSelected(False) for n in nuke.allNodes(recurseGroups=True)]\n\ndef expand_group():\n    # nuke.expandSelectedGroup() # not an option: reverses input order\n    node = nuke.thisNode()\n    node.begin()\n    brackets = node\['brackets'].getValue()\n    \n    # Copy used nodes inside group\n    _ = \[n.setSelected(True) for n in nuke.allNodes()]\n    for n in nuke.selectedNodes(): # remove unused brackets\n        lastchar = n.name()\[-1]\n        if lastchar.isdigit():\n            if int(lastchar) >= brackets:\n                n.setSelected(False)\n    nuke.nodeCopy('%clipboard')\n\n    # Paste nodes to root \n    nuke.root().begin()\n    unselect()\n    nuke.nodePaste('%clipboard')\n    copied_nodes = nuke.selectedNodes()\n    \n    # Move ungrouped nodes to 0th input of node\n    input0 = nuke.toNode('Input0')\n    offset = (input0.xpos() - node.input(0).xpos(), input0.ypos() - node.input(0).ypos())\n    _ = \[n.setXYpos(n.xpos() - offset\[0], n.ypos() - offset\[1]) for n in copied_nodes]\n    \n    # Reconnect Input nodes\n    for i in range(node.inputs()):\n        inputNode = nuke.toNode('Input\{0\}'.format(i))\n        inputNode.setInput(0, node.input(i))\n\n    # Delete Inputs and Output\n    _ = \[nuke.delete(n) for n in copied_nodes if n.Class() in \['Input', 'Output']]\n    \n    # Move ExposureBlend node out of the way\n    node.setXYpos(node.xpos()-400, node.ypos())\n    \n\nexpand_group()"}
 addUserKnob {22 create_equalize_exposure l "Create EqualizeExposure" t "Create an EqualizeExposure node on selected" -STARTLINE T "def unselect(): \n    _ = \[n.setSelected(False) for n in nuke.allNodes('recurseGroups=True')]\ndef create_mult(exp_val=1, target=None):\n    if target:\n        unselect()\n        target.setSelected(True)\n    mult = nuke.createNode('Multiply')\n    mult\['channels'].setValue('rgb')\n    mult.setName('EqualizeExposure')\n    mult.addKnob(nuke.Tab_Knob('exposure_tab', 'exposure'))\n    mult.addKnob(nuke.Double_Knob('exposure', 'exposure'))\n    mult\['value'].setExpression('exposure/\[metadata input/exposure_time]')\n    mult\['exposure'].setValue(exp_val)\n    return mult\n    \nnode = nuke.thisNode()\nexp_val = node\['exposure'].getValue()\nnuke.root().begin()\nsel = nuke.selectedNodes()\nmults = list()\nif sel:\n    for n in sel:\n        mults.append(create_mult(exp_val, n))\nelse:\n    mults.append(create_mult(exp_val))\n_ = \[n.setSelected(True) for n in mults]"}
 addUserKnob {41 brackets T P.brackets}
 addUserKnob {41 exposure T P.exposure}
 addUserKnob {41 noise_floor l "noise floor" T P.noise_floor}
 addUserKnob {41 falloff T P.falloff}
 addUserKnob {41 center T P.center}
 addUserKnob {20 keyer_ranges_grp l "Keyer Ranges" t "Show the Keyers for each bracket, for visualization" n 1}
 keyer_ranges_grp 0
 addUserKnob {41 kr_0 l "" +STARTLINE T Keyer0.range}
 addUserKnob {41 kr_1 l "" +STARTLINE T Keyer1.range}
 addUserKnob {41 kr_2 l "" +STARTLINE T Keyer2.range}
 addUserKnob {41 kr_3 l "" +STARTLINE T Keyer3.range}
 addUserKnob {41 kr_4 l "" +STARTLINE T Keyer4.range}
 addUserKnob {41 kr_5 l "" +STARTLINE T Keyer5.range}
 addUserKnob {41 kr_6 l "" +STARTLINE T Keyer6.range}
 addUserKnob {20 endGroup n -1}
}
 Input {
  inputs 0
  name Input9
  xpos 950
  ypos 206
  number 9
 }
 Keyer {
  operation "luminance key"
  range {{lerp(P.noise_floor,0,(number+1)/P.brackets)} {lerp(A,lerp(A,P.center,P.falloff),1-(number+1)/P.brackets)} {lerp(D,lerp(D,P.center,P.falloff),(number+1)/P.brackets)} 0.99999}
  name Keyer9
  label "num \[value number]"
  xpos 950
  ypos 248
  addUserKnob {20 Params}
  addUserKnob {3 number}
  number 9
  addUserKnob {6 start -STARTLINE}
  start {{number==0}}
  addUserKnob {6 end -STARTLINE}
  end {{number==(P.brackets-1)}}
 }
 Multiply {
  channels rgb
  value {{"exposure/\[metadata input/exposure_time]"}}
  name EqualizeExposure9
  label "\[value value]"
  xpos 950
  ypos 296
  addUserKnob {20 exposure_tab l exposure}
  addUserKnob {7 exposure}
  exposure {{P.exposure}}
 }
 Premult {
  name Premult9
  xpos 950
  ypos 374
 }
 Input {
  inputs 0
  name Input8
  xpos 840
  ypos 206
  number 8
 }
 Keyer {
  operation "luminance key"
  range {{lerp(P.noise_floor,0,(number+1)/P.brackets)} {lerp(A,lerp(A,P.center,P.falloff),1-(number+1)/P.brackets)} {lerp(D,lerp(D,P.center,P.falloff),(number+1)/P.brackets)} 0.99999}
  name Keyer8
  label "num \[value number]"
  xpos 840
  ypos 248
  addUserKnob {20 Params}
  addUserKnob {3 number}
  number 8
  addUserKnob {6 start -STARTLINE}
  start {{number==0}}
  addUserKnob {6 end -STARTLINE}
  end {{number==(P.brackets-1)}}
 }
 Multiply {
  channels rgb
  value {{"exposure/\[metadata input/exposure_time]"}}
  name EqualizeExposure8
  label "\[value value]"
  xpos 840
  ypos 296
  addUserKnob {20 exposure_tab l exposure}
  addUserKnob {7 exposure}
  exposure {{P.exposure}}
 }
 Premult {
  name Premult8
  xpos 840
  ypos 374
 }
 Input {
  inputs 0
  name Input7
  xpos 730
  ypos 206
  number 7
 }
 Keyer {
  operation "luminance key"
  range {{lerp(P.noise_floor,0,(number+1)/P.brackets)} {lerp(A,lerp(A,P.center,P.falloff),1-(number+1)/P.brackets)} {lerp(D,lerp(D,P.center,P.falloff),(number+1)/P.brackets)} 0.99999}
  name Keyer7
  label "num \[value number]"
  xpos 730
  ypos 248
  addUserKnob {20 Params}
  addUserKnob {3 number}
  number 7
  addUserKnob {6 start -STARTLINE}
  start {{number==0}}
  addUserKnob {6 end -STARTLINE}
  end {{number==(P.brackets-1)}}
 }
 Multiply {
  channels rgb
  value {{"exposure/\[metadata input/exposure_time]"}}
  name EqualizeExposure7
  label "\[value value]"
  xpos 730
  ypos 296
  addUserKnob {20 exposure_tab l exposure}
  addUserKnob {7 exposure}
  exposure {{P.exposure}}
 }
 Premult {
  name Premult7
  xpos 730
  ypos 374
 }
 Input {
  inputs 0
  name Input6
  xpos 620
  ypos 206
  number 6
 }
 Keyer {
  operation "luminance key"
  range {{lerp(P.noise_floor,0,(number+1)/P.brackets)} {lerp(A,lerp(A,P.center,P.falloff),1-(number+1)/P.brackets)} {lerp(D,lerp(D,P.center,P.falloff),(number+1)/P.brackets)} 0.99999}
  name Keyer6
  label "num \[value number]"
  xpos 620
  ypos 248
  addUserKnob {20 Params}
  addUserKnob {3 number}
  number 6
  addUserKnob {6 start -STARTLINE}
  start {{number==0}}
  addUserKnob {6 end -STARTLINE}
  end {{number==(P.brackets-1)}}
 }
 Multiply {
  channels rgb
  value {{"exposure/\[metadata input/exposure_time]"}}
  name EqualizeExposure6
  label "\[value value]"
  xpos 620
  ypos 296
  addUserKnob {20 exposure_tab l exposure}
  addUserKnob {7 exposure}
  exposure {{P.exposure}}
 }
 Premult {
  name Premult6
  xpos 620
  ypos 374
 }
 Input {
  inputs 0
  name Input5
  xpos 510
  ypos 206
  number 5
 }
 Keyer {
  operation "luminance key"
  range {{lerp(P.noise_floor,0,(number+1)/P.brackets)} {lerp(A,lerp(A,P.center,P.falloff),1-(number+1)/P.brackets)} {lerp(D,lerp(D,P.center,P.falloff),(number+1)/P.brackets)} 0.99999}
  name Keyer5
  label "num \[value number]"
  xpos 510
  ypos 248
  addUserKnob {20 Params}
  addUserKnob {3 number}
  number 5
  addUserKnob {6 start -STARTLINE}
  start {{number==0}}
  addUserKnob {6 end -STARTLINE}
  end {{number==(P.brackets-1)}}
 }
 Multiply {
  channels rgb
  value {{"exposure/\[metadata input/exposure_time]"}}
  name EqualizeExposure5
  label "\[value value]"
  xpos 510
  ypos 296
  addUserKnob {20 exposure_tab l exposure}
  addUserKnob {7 exposure}
  exposure {{P.exposure}}
 }
 Premult {
  name Premult5
  xpos 510
  ypos 374
 }
 Input {
  inputs 0
  name Input4
  xpos 400
  ypos 206
  number 4
 }
 Keyer {
  operation "luminance key"
  range {{lerp(P.noise_floor,0,(number+1)/P.brackets)} {lerp(A,lerp(A,P.center,P.falloff),1-(number+1)/P.brackets)} {lerp(D,lerp(D,P.center,P.falloff),(number+1)/P.brackets)} 0.99999}
  name Keyer4
  label "num \[value number]"
  xpos 400
  ypos 248
  addUserKnob {20 Params}
  addUserKnob {3 number}
  number 4
  addUserKnob {6 start -STARTLINE}
  start {{number==0}}
  addUserKnob {6 end -STARTLINE}
  end {{number==(P.brackets-1)}}
 }
 Multiply {
  channels rgb
  value {{"exposure/\[metadata input/exposure_time]"}}
  name EqualizeExposure4
  label "\[value value]"
  xpos 400
  ypos 296
  addUserKnob {20 exposure_tab l exposure}
  addUserKnob {7 exposure}
  exposure {{P.exposure}}
 }
 Premult {
  name Premult4
  xpos 400
  ypos 374
 }
 Input {
  inputs 0
  name Input3
  xpos 290
  ypos 206
  number 3
 }
 Keyer {
  operation "luminance key"
  range {{lerp(P.noise_floor,0,(number+1)/P.brackets)} {lerp(A,lerp(A,P.center,P.falloff),1-(number+1)/P.brackets)} {lerp(D,lerp(D,P.center,P.falloff),(number+1)/P.brackets)} 0.99999}
  name Keyer3
  label "num \[value number]"
  xpos 290
  ypos 248
  addUserKnob {20 Params}
  addUserKnob {3 number}
  number 3
  addUserKnob {6 start -STARTLINE}
  start {{number==0}}
  addUserKnob {6 end -STARTLINE}
  end {{number==(P.brackets-1)}}
 }
 Multiply {
  channels rgb
  value {{"exposure/\[metadata input/exposure_time]"}}
  name EqualizeExposure3
  label "\[value value]"
  xpos 290
  ypos 296
  addUserKnob {20 exposure_tab l exposure}
  addUserKnob {7 exposure}
  exposure {{P.exposure}}
 }
 Premult {
  name Premult3
  xpos 290
  ypos 374
 }
 Input {
  inputs 0
  name Input2
  xpos 180
  ypos 206
  number 2
 }
 Keyer {
  operation "luminance key"
  range {{lerp(P.noise_floor,0,(number+1)/P.brackets)} {lerp(A,lerp(A,P.center,P.falloff),1-(number+1)/P.brackets)} {lerp(D,lerp(D,P.center,P.falloff),(number+1)/P.brackets)} 0.99999}
  name Keyer2
  label "num \[value number]"
  xpos 180
  ypos 248
  addUserKnob {20 Params}
  addUserKnob {3 number}
  number 2
  addUserKnob {6 start -STARTLINE}
  start {{number==0}}
  addUserKnob {6 end -STARTLINE}
  end {{number==(P.brackets-1)}}
 }
 Multiply {
  channels rgb
  value {{"exposure/\[metadata input/exposure_time]"}}
  name EqualizeExposure2
  label "\[value value]"
  xpos 180
  ypos 296
  addUserKnob {20 exposure_tab l exposure}
  addUserKnob {7 exposure}
  exposure {{P.exposure}}
 }
 Premult {
  name Premult2
  xpos 180
  ypos 374
 }
push 0
 Input {
  inputs 0
  name Input1
  xpos 70
  ypos 206
  number 1
 }
 Keyer {
  operation "luminance key"
  range {{lerp(P.noise_floor,0,(number+1)/P.brackets)} {lerp(A,lerp(A,P.center,P.falloff),1-(number+1)/P.brackets)} {lerp(D,lerp(D,P.center,P.falloff),(number+1)/P.brackets)} 0.99999}
  name Keyer1
  label "num \[value number]"
  xpos 70
  ypos 248
  addUserKnob {20 Params}
  addUserKnob {3 number}
  number 1
  addUserKnob {6 start -STARTLINE}
  start {{number==0}}
  addUserKnob {6 end -STARTLINE}
  end {{number==(P.brackets-1)}}
 }
 Multiply {
  channels rgb
  value {{"exposure/\[metadata input/exposure_time]"}}
  name EqualizeExposure1
  label "\[value value]"
  xpos 70
  ypos 296
  addUserKnob {20 exposure_tab l exposure}
  addUserKnob {7 exposure}
  exposure {{P.exposure}}
 }
 Premult {
  name Premult1
  xpos 70
  ypos 374
 }
 Input {
  inputs 0
  name Input0
  xpos -40
  ypos 206
 }
 Keyer {
  operation "luminance key"
  range {{lerp(P.noise_floor,0,(number+1)/P.brackets)} {lerp(A,lerp(A,P.center,P.falloff),1-(number+1)/P.brackets)} {lerp(D,lerp(D,P.center,P.falloff),(number+1)/P.brackets)} 0.99999}
  name Keyer0
  label "num \[value number]"
  xpos -40
  ypos 247
  addUserKnob {20 Params}
  addUserKnob {3 number}
  addUserKnob {6 start -STARTLINE}
  start {{number==0}}
  addUserKnob {6 end -STARTLINE}
  end {{number==(P.brackets-1)}}
 }
 Multiply {
  channels rgb
  value {{"exposure/\[metadata input/exposure_time]"}}
  name EqualizeExposure0
  label "\[value value]"
  xpos -40
  ypos 296
  addUserKnob {20 exposure_tab l exposure}
  addUserKnob {7 exposure}
  exposure {{P.exposure}}
 }
 Premult {
  name Premult0
  xpos -40
  ypos 374
 }
 Merge2 {
  inputs 10+1
  operation plus
  name MergePlus
  xpos -40
  ypos 504
 }
 Dot {
  name P
  tile_color 0xff0000ff
  label " P"
  note_font_size 24
  note_font_color 0xa5a5a501
  xpos -6
  ypos 570
  addUserKnob {20 Params_tab l Params}
  addUserKnob {3 brackets}
  brackets 7
  addUserKnob {7 exposure R 0 10}
  exposure 1
  addUserKnob {7 noise_floor l "noise floor" R 0 0.1}
  noise_floor 0.008
  addUserKnob {7 falloff}
  falloff 1
  addUserKnob {7 center}
  center 0.18
 }
set Nd881b370 [stack 0]
 Shuffle {
  red alpha
  green alpha
  blue alpha
  name ShuffleAlpha
  xpos -150
  ypos 566
 }
push $Nd881b370
 MergeExpression {
  inputs 2
  expr0 Ar==0?0:Br/Ar
  expr1 Ag==0?0:Bg/Ag
  expr2 Ab==0?0:Bb/Ab
  channel3 alpha
  expr3 Aa==0?0:Ba/Aa
  name MergeDivideReverse
  xpos -40
  ypos 614
 }
 Dot {
  name OUT
  xpos -6
  ypos 700
 }
 Output {
  name Output
  xpos -40
  ypos 751
 }
end_group

Hi Jed,
I'm trying to use your script, but when i use it (import script), nuke shell return an error (before using any function of the node) : "ERROR: ExposureBlend.Extract0._m: Nothing is named "metadata"" (error is repeted from Extract0 to 9).
And when i try to use the node (sort selected Reads), it sorts the exr file and then disappear before doing any modification or exposureblend...
Any help will be greatly appreciated :)
And i must thank you for your other scripts - specially Debayer which is awesome

Hi Jed,

Is there an updated version of this tool? This one looks slightly different to the one shown here:
https://youtu.be/Xn5GTLK0ewc?t=1370
as it has Expression nodes rather than Keyer nodes and lacks the ranges dropdown (maybe that's only created when the button scripts completes). Also there's a few hardcoded assumptions which cause it to fail like the exif key for DateTime and the format of the ExposureTime value

thanks

Hello @frenchie1980,
Thanks for the flag, I just pushed an update from nuke-config into this gist.

Yeah there are a few improvements that could be made to this tool for sure. In addition to the DateTime exif key and the exposure time value it owuld be useful to add a user parameter to set the threshold between exposures for the exposure set detection. Maybe I'll have time to get to this one of these days...

Thanks so much Jed,

Wow that nuke-config repo looks like a goldmine. Will have a look through it. Since I need this exposureblend tool (or something like it) now, I'm gonna make some local amends for things like the exif field and simple fixes of any non-py3 print statements. Then happy to put in a PR for you to check out

pushed a few little updates for python 3 support (jeeze finally), and also exposed a parameter for specifying the threshold in seconds between bracketed exposure sets.