1 The idea
Each depth zone has its own black. Far things sit behind more air, so their black is lifted and tinted. CG must get the black of the zone it stands in.
This is the same exercise as lesson 03, placed in the Integration pack so it leads into haze and light wrap.
2 Hands-on
3 Deep dive
A black point is a colour per place, not one number
A black point is the colour a perfectly black object would show if you placed it at that spot in the frame. The air between camera and object, glare inside the lens and nearby coloured light all lift and tint that black.
In the figure’s plate the near ground is nearly black, while the far ridge sits behind haze, so its black is lifted and tinted by the air. The CG tower stands on that far ridge, so it takes the far zone’s lifted, haze-tinted black, not the near ground’s black and not the darkest pixel in the frame.
| Zone | Where to sample | What its black looks like |
|---|---|---|
| Near (foreground ground) | The darkest patch of the near ground | Lowest, but not 0 |
| Mid (middle hills) | Dark side of a hill at the same distance | Slightly lifted |
| Far (the ridge the tower stands on) | Shadow pockets on the ridge beside the tower | Clearly lifted and tinted by the air |
The rules that decide it
A nearer object must not have more lifted blacks than a farther one, unless a local light or flare explains it. Two depth planes should never share the exact same black, or the eye loses the sense of distance; give the farther plane a touch more lift.
CG should not sit at pure 0, because a real camera always has some grain and bounce light. And don’t force the black to neutral: if the plate’s blacks lean blue or orange, the CG blacks lean the same way.
CG blacks: never darker than the plate beside them, never more lifted than things farther away.
Toe lifts only the darks; Grade lift moves everything
Grade lift pivots at 1: it raises darks and mids but pulls values above 1 down. The CG tower in the figure has a 4.5 sun glint, so a Grade lift would dull it. Toe raises the floor with a soft roll-off and leaves anything above twice the lift value untouched.
The numbers below were tested in Nuke (a 0.1 lift with each node). The toe in this lesson’s figure is a teaching curve that leaves values from 0.4 up alone, not the real Toe2 formula, so its dark values differ slightly from the table.
| Input | Grade lift 0.1 | Toe lift 0.1 |
|---|---|---|
| 0 | 0.10 | 0.10 |
| 0.1 | 0.19 | 0.125 |
| 0.2 | 0.28 | 0.20 (untouched) |
| 1.0 | 1.00 | 1.00 |
| 4.5 (sun glint) | 4.15 (pulled down) | 4.50 |
Where it goes: black match is the last colour step
Finish every grade on the element first, then match the black on its own node, last. Any grade after it moves the black you just matched, and you end up re-fixing it every time you brighten the element. This rule covers the element’s own colour work. If you add depth haze to the element (I2), the haze goes after the Toe, and scene-wide look grades come after the merge; re-check the blacks with the viewer gamma up after each of those.
Keep the viewer gamma pushed up the whole time you work on blacks: the darks open up and zone differences become obvious. Switch to luminance only, so colour doesn’t distract you.
- 1Unpremult
- 2Colour / white grades
- 3Toe black match
- 4Premult
- 5Merge over
4 In real work
In Nuke
- Unpremult → Grade (colour balance and white point) first.
- Toe (class name Toe2): use the colour picker to sample the plate black in the same zone into lift.
- If the element spans several depths, use one Toe per zone, each limited by a mask (Roto or depth).
- Premult → Merge (over) onto the plate. No Grade after the Toe (the one exception is depth haze from I2, if you use it).
- Check: push the viewer gamma up and wipe against the plate.
Common mistakes → the fix
- ✗ Using Grade lift to raise blacks on an element with HDR values✓ Use Toe: it lifts only the darks and leaves values above 1 alone.
- ✗ One black value for the whole frame✓ Sample a black per depth zone; farther zones are more lifted.
- ✗ Adding a Grade after the black-match node✓ Move look changes above it; the black match stays last.
- ✗ Neutralising the black when the plate’s blacks are tinted✓ Sample the plate black in all three channels so the CG carries the same tint.
Before you send the shot
- With the viewer gamma up, the tower’s shadow side sits with the ridge beside it.
- Nothing near has more lifted blacks than something far.
- No two depth planes share exactly the same black.
- No CG pixel sits at exactly 0.
- The 4.5 sun glint is as bright as before the black match.
- The black match is the last grade before Premult (only depth haze, if used, sits after it).
5 Check yourself
Should two depth planes share one black?
🔒 Answer the question above and this card opens
1. The CG tower’s shadow side reads 0, the far ridge’s black beside it about 0.13 / 0.15 / 0.18 (r g b), and the near ground’s black about 0.01. What should you do?
2. The CG tower has a sun glint at 4.5 and needs a 0.1 black lift. Which node is best?
Where the numbers come from: Grade lift 0.1 turns 4.5 into 4.15 (checked in Nuke 17). The toe in the figure is an example curve that only touches values below 0.4, not the exact Toe2 formula. The plate is drawn in code in your browser.