Tone Compression in Nuke

I recently packaged up a Nuke setup for compressing values in images to a single “compressor” node and wanted to share it. It’s sometimes useful to be able to compress or roll off high values in comps, either for technical reasons (to match the pixel limit of the sensor that captured the plate or extract just the detail or colour info) or for more creative reasons (pulling down the top end of a comp without breaking anything). This can be done using Nuke’s build in nodes such as the SoftClip or combining a string of Clamp nodes to gradually roll off highlights. However the opposite is also useful sometimes too - compressing either just shadows, or highlights as well to flatten the entire image in a smooth way. I wanted to emulate Adobe’s methods of shadow/highlight control in their Camera Raw Utility, which manages to compress in a very subtle and understated way, rarely with any artefacts. I also built into this Nuke setup a way to push tone compression in a “tone mapping” sort of way for a HDR aesthetic, which uses frequency information as well as simple pixel values. The general method uses multiplication of highlights in log space (flipped for the shadows) in separated frequencies.

The shadow/highlights parameter is a ratio to balance how much of either you affect. 0.5 is an equal mix, and the image will compress at the top and bottom end.

Shadow and highlight ranges control how much of the tones will be affected.

Tonemapping will flatten the image in a HDR-like way, with the radius slider controlling the pixel frequencies defining the edges in the image.

For subtle “rolloff” use, lower radius values down to 0 work fine, and tonemapping can be left alone.

Example 3D scene before any compression

Highlight compression, shadow compression, extreme tonemapping

The script for the tool:

set cut_paste_input [stack 0]
version 12.1 v2
push $cut_paste_input
Group {
name CT_Compressor
tile_color 0xca86600
selected true
xpos 48
ypos 6810
addUserKnob {20 CTCompressor l "CT Compressor"}
addUserKnob {7 compress R 0 2}
addUserKnob {7 balance l shadows/highlights}
balance 0.5
addUserKnob {26 ""}
addUserKnob {7 shadowRange l "shadow range" R 0 2}
shadowRange 1
addUserKnob {7 highlightRange l "highlight range" R 0 2}
highlightRange 1
addUserKnob {26 ""}
addUserKnob {7 restore l tonemapping}
restore 0.3
addUserKnob {7 detail l radius R 0 3}
detail 0.5
}
Input {
inputs 0
name image
selected true
xpos 1190
ypos 141
}
Log2Lin {
operation lin2log
name Log2Lin3
xpos 1149
ypos 405
}
Dot {
name Dot13
xpos 1162
ypos 473
}
set N736f7440 [stack 0]
Dot {
name Dot3
xpos 885
ypos 473
}
Dot {
name Dot2
xpos 879
ypos 1227
}
push $N736f7440
Group {
name diffusion
xpos 1120
ypos 584
addUserKnob {20 User}
addUserKnob {41 size T Blur1.size}
}
Input {
inputs 0
name Input1
xpos -8
ypos -105
}
Dot {
name Dot1
xpos 26
ypos -79
}
Dot {
name Dot2
xpos 278
ypos 24
}
set N731e4b80 [stack 0]
Blur {
size {{parent.Blur1.size*16}}
name Blur5
xpos 911
ypos 137
}
push $N731e4b80
Blur {
size {{parent.Blur1.size*8}}
name Blur4
xpos 623
ypos 119
}
push $N731e4b80
Blur {
size {{parent.Blur1.size*4}}
name Blur3
xpos 486
ypos 118
}
push $N731e4b80
Blur {
size {{parent.Blur1.size*2}}
name Blur2
xpos 358
ypos 111
}
push $N731e4b80
Blur {
size {{(parent.parent.compress*50)*detail}}
name Blur1
xpos 244
ypos 114
}
Dissolve {
inputs 2
which 0.5
name Dissolve1
xpos 314
ypos 176
}
Dissolve {
inputs 2
which 0.25
name Dissolve2
xpos 486
ypos 176
}
Dissolve {
inputs 2
which 0.125
name Dissolve3
xpos 623
ypos 176
}
Dissolve {
inputs 2
which 0.0625
name Dissolve4
xpos 817
ypos 176
}
Output {
name Output1
xpos 817
ypos 436
}
end_group
Dot {
name Dot19
xpos 1154
ypos 650
}
set Na5efeab0 [stack 0]
push $N736f7440
Dot {
name Dot1
xpos 1573
ypos 473
}
Merge2 {
inputs 2
operation from
name Merge12
xpos 1613
ypos 623
}
Dot {
name Dot18
xpos 1564
ypos 1152
}
push $Na5efeab0
Dot {
name Dot15
xpos 1141
ypos 706
}
set N13f70cd0 [stack 0]
push $N13f70cd0
Invert {
channels rgb
name Invert4
xpos 1136
ypos 763
}
Multiply {
channels rgb
value {{parent.shadowRange}}
name Multiply1
xpos 1136
ypos 789
}
ColorCorrect {
highlights.offset {{1-((compress*(1-balance))+1)}}
lookup {shadow {}
  midtone {}
  highlight {curve x0.265168488 0 s0 x1.309550405 0.9974999428 s0}}
name shads
xpos 1136
ypos 815
}
Multiply {
channels rgb
value {{1/parent.Multiply1.value}}
name Multiply2
xpos 1136
ypos 841
}
Invert {
channels rgb
name Invert2
xpos 1136
ypos 867
}
Dot {
name Dot11
xpos 1180
ypos 997
}
set N57f919c0 [stack 0]
Merge2 {
inputs 2
operation divide
name Merge10
xpos 1457
ypos 969
}
push $N57f919c0
Merge2 {
inputs 2
operation multiply
mix {{1-restore}}
name Merge11
xpos 1167
ypos 1090
}
Merge2 {
inputs 2
operation plus
name Merge13
xpos 1167
ypos 1148
}
Merge2 {
inputs 2
operation max
name Merge1
xpos 1188
ypos 1223
}
Dot {
name Dot4
xpos 1222
ypos 1358
}
set N803fc9d0 [stack 0]
Dot {
name Dot12
xpos 958
ypos 1383
}
Dot {
name Dot5
xpos 984
ypos 2047
}
push $N803fc9d0
Group {
name diffusion2
xpos 1236
ypos 1501
addUserKnob {20 User}
addUserKnob {41 size T Blur1.size}
}
Input {
inputs 0
name Input1
xpos -8
ypos -105
}
Dot {
name Dot1
xpos 26
ypos -79
}
Dot {
name Dot2
xpos 278
ypos 24
}
set N729fcdb0 [stack 0]
Blur {
size {{parent.Blur1.size*16}}
name Blur5
xpos 911
ypos 137
}
push $N729fcdb0
Blur {
size {{parent.Blur1.size*8}}
name Blur4
xpos 623
ypos 119
}
push $N729fcdb0
Blur {
size {{parent.Blur1.size*4}}
name Blur3
xpos 486
ypos 118
}
push $N729fcdb0
Blur {
size {{parent.Blur1.size*2}}
name Blur2
xpos 358
ypos 111
}
push $N729fcdb0
Blur {
size {{(parent.parent.compress*50)*detail}}
name Blur1
xpos 244
ypos 114
}
Dissolve {
inputs 2
which 0.5
name Dissolve1
xpos 314
ypos 176
}
Dissolve {
inputs 2
which 0.25
name Dissolve2
xpos 486
ypos 176
}
Dissolve {
inputs 2
which 0.125
name Dissolve3
xpos 623
ypos 176
}
Dissolve {
inputs 2
which 0.0625
name Dissolve4
xpos 817
ypos 176
}
Output {
name Output1
xpos 817
ypos 436
}
end_group
Dot {
name Dot6
xpos 1270
ypos 1567
}
set N754f9120 [stack 0]
push $N803fc9d0
Dot {
name Dot7
xpos 1672
ypos 1389
}
Merge2 {
inputs 2
operation from
name Merge2
xpos 1712
ypos 1539
}
Dot {
name Dot8
xpos 1669
ypos 1972
}
push $N754f9120
Dot {
name Dot9
xpos 1270
ypos 1614
}
set N71ff84b0 [stack 0]
push $N71ff84b0
Multiply {
channels rgb
value {{parent.highlightRange}}
name Multiply3
xpos 1252
ypos 1663
}
ColorCorrect {
highlights.gain {{1-(compress*(balance))}}
lookup {shadow {}
  midtone {}
  highlight {curve x0.265168488 0 s0 x1.014901519 0.9974999428 s0}}
name highlights
xpos 1252
ypos 1689
}
Clamp {
channels rgb
minimum 1e-05
maximum_enable false
name Clamp1
xpos 1258
ypos 1716
}
set N71ef3050 [stack 0]
Multiply {
channels rgb
value {{1/parent.Multiply3.value}}
name Multiply4
xpos 1252
ypos 1753
}
Dot {
name Dot10
xpos 1306
ypos 1800
}
set N71dfdc20 [stack 0]
Merge2 {
inputs 2
operation divide
name Merge3
xpos 1543
ypos 1796
}
push $N71dfdc20
Merge2 {
inputs 2
operation multiply
mix {{1-restore}}
name Merge4
xpos 1272
ypos 1876
}
Merge2 {
inputs 2
operation plus
name Merge5
xpos 1272
ypos 1968
}
Merge2 {
inputs 2
operation min
name Merge6
xpos 1293
ypos 2043
}
Dot {
name Dot14
xpos 1308
ypos 2139
}
Log2Lin {
name Log2Lin4
xpos 1274
ypos 2206
}
set N716f9f10 [stack 0]
push 0
push 0
push 0
push 0
push 0
push 0
push 0
push $N71ef3050
push $N716f9f10
Output {
name Output1
xpos 1271
ypos 2776
}
Viewer {
inputs 10
frame 1129
frame_range 989-989
colour_sample_bbox {-0.06591796875 0.1059570312 -0.0654296875 0.1062011719}
name Viewer1
xpos 2490
ypos -10
}
end_group