1 The idea
Symptom: the robot looks like a sticker on the plate, even though its overall colour and light seem fine. Probe its darkest crevice: almost 0. The crevice of the right-hand rock, at about the same distance, reads about 0.013 / 0.012 / 0.011. Nothing in a real plate is pure black, because air and lens glare sit between the camera and every object.
In real work the cause is often a lookdev grade that gave the CG "punch" and sank its blacks. The fix is a Toe as the element’s last colour operation: raise the black floor to the plate’s black at the same distance, without touching the mids and highlights. Don’t match the near rock at the bottom left: it is closer to camera, so its black is deeper (about 0.007 / 0.006 / 0.004: warmer from the sand bounce, and darker in every channel).
Toe: floor = lift, only the darks move2 Hands-on in the mini compositor
Task: set the "Toe (black match)" lift to r 0.013, g 0.012, b 0.011 so the robot’s black equals the rock at its distance
Push the Viewer gamma to about 2 and compare the robot’s crevices with the rock’s, before and after
3 Deep dive
Black is not one number, it is a colour per distance
Nothing in a real photo is truly black. Between the camera and every object there is air, dust and glare inside the lens, so distant things have a lifted, tinted black floor, while near things go deeper.
A simple sanity rule: a nearer object must not have a more lifted black than a farther one, unless a light or flare explains it. CG darker than everything around it pops out like a sticker.
| Measured in this lesson’s plate | Darkest (r g b) | Meaning |
|---|---|---|
| Near rock, bottom left | 0.007 0.006 0.004 | Near: deepest (luma 0.006) |
| Right rock, robot’s distance | 0.013 0.012 0.011 | The robot’s target (luma 0.012) |
| Far rock, right of centre | 0.026 0.022 0.017 | Far: lifted (luma 0.023) |
Why a Toe, not a Grade lift
A Grade lift pivots around white: it raises the blacks but also pulls values above 1 down, dulling the CG’s lights and highlights. A Toe raises only the black floor and fades out before the mids. In Nuke 17, Toe stops acting at 2× its lift value.
- 1Unpremult
- 2Grade mids/highs
- 3Toe (black match) last
- 4Premult
- 5Merge over
The black match is the element’s last colour operation
How to measure it properly
Switch the black-raising node off and sample the CG’s darkest spot. Then find something in the plate at a similar distance, in shadow, and sample its darkest crevice. Put that value in the lift and switch the node back on.
Check with the Viewer gamma up at about 2–3: the CG’s black should melt into the rock crevice beside it, neither deeper nor floating above. If the CG sits between two zones, use a value in between.
4 In real work
In Nuke
- Read CG → Unpremult → Grade (mids/highs) → Toe → Premult → Merge over
- Viewer: Ctrl/Cmd-click samples a pixel; Ctrl/Cmd-Shift-drag samples an area average
- Toe: enter the plate’s black at the same distance in lift, per r g b
- With several distances, use one Toe per element or per depth zone
Common mistakes → the fix
- ✗ Matching the CG black to the darkest pixel in frame✓ Compare with things at the CG’s distance; the darkest pixel is usually near camera.
- ✗ Using a Grade lift to raise the whole element’s blacks✓ Use a Toe, which touches only the blacks; a lift drags the whole range and dulls highlights.
- ✗ Grading again after the black match✓ Keep the black match last, or the measured black drifts.
- ✗ Giving every distance the same black✓ Lift the far ones a little more, or the image loses depth.
Before you send the shot
- CG black compared with things at its distance, Viewer gamma up
- Nothing near has a higher black than something far
- The Toe is the element’s last colour operation
- The CG’s highlights and lights didn’t dull
5 Check yourself
What makes the robot look pasted on in this case?
🔒 Answer the question above and this card opens
1. The robot is mid-distance. A near rock’s black is 0.006; a rock at the robot’s distance is 0.012. What black should the robot get?
2. Why is a Grade lift a poor black match for CG with lights above 1?
Where the numbers come from: The rock’s black was measured from this plate (the minimum in the right rock’s crevice). The Toe here is a teaching version: floor = lift, values from 0.4 up untouched; Nuke’s own Toe stops acting at 2× the lift (checked in Nuke 17). Same principle.