RESOLVE FX · KEY
Luma
Keyer.
Key brightness.
Do not ask luminance to understand color.
Luma Keyer is the deliberately one-dimensional member of Resolve FX Key: sample luminance, define core range and falloff, then refine the resulting matte only as much as necessary. Its simplicity is an advantage when brightness separates the subject—and a hard limit when it does not.
Luminance only
Matte Finesse 1 / 2
B/W → Composite
The lab is an independent teaching model for range, falloff and matte cleanup. It does not reproduce Resolve’s private sampling math or parameter scales.
Matte Finesse · Bank 1
This lab uses independent educational range masks and simple spatial filtering. Its numeric sliders are not Resolve parameter scales.
Independent teaching model. It demonstrates range versus softness, polarity, matte cleanup and output inspection. It does not reproduce Resolve’s internal luminance coefficients, sampling accumulation, Matte Finesse algorithms, GPU implementation or parameter scales.
Three native Inspector captures + an independent luminance-key lab.
Range · Softness · Matte · Output01ONE DIMENSION, USED DELIBERATELY
Brightness decides membership; downstream tools only reshape the answer.
Blackmagic describes Luma Keyer as HSL Keyer with H and S disabled. That makes its mental model unusually clean: first decide which luminance values belong, then decide how soft and usable the resulting matte should be.
Select brightness, not color
Luma Keyer evaluates luminance only. That is powerful when the target separates tonally and a limitation when foreground and background share similar brightness but differ in color. Extra matte cleanup cannot add chroma information that was never part of the selection.
Range and Softness solve different problems
Sample/Add/Subtract Luma Range define the fully selected core brightness range. Add/Subtract Softness alter the falloff around that core. If another brightness level must belong to the key, change Range; if the level is already selected but the transition is too hard, change Softness.
Matte Finesse is downstream of selection
Pre Filter, Clean, Clip, Blur and In/Out Ratio filter the keyer output. They can help chatter, holes and contamination, but extreme values quickly turn a sampling mistake into a thick, synthetic edge. Build selection first, then clean it, then judge the composite.
Stable behavior reference: Blackmagic Design · Luma Keyer ↗
02THE ACTUAL RESOLVE 21 PANEL
Three native captures anchor the controls to the real interface.
The full capture shows the five sampling icons, Invert, Reset and Matte Finesse Bank 1. Separate native menus verify Garbage Matte and Output choices. Captured values are evidence, not presets.
SELECTION RANGE
Build the luminance family first
- Sample Eyedropper
Creates the initial luminance range. A click samples one value; a drag collects a range. This is the first sampling tool; the other four refine an existing selection.
CheckOn the Edit page, verify the Viewer Overlay is Open FX Overlay; sample a representative area rather than a random pixel.
- Add Luma Range
Expands the core selection to additional luminance values. This changes membership in the key; it is not feathering.
CheckIf target and foreground overlap in brightness, a large Add Range captures unwanted regions at the same time.
- Subtract Luma Range
Removes incorrectly captured luminance values from the fully selected core. Useful after an overly broad drag or for a tonal island inside the target range.
CheckIf many different pieces need subtraction, Reset and a cleaner new sample is often faster.
- Add Softness
Expands the outer falloff between selected and unselected brightness. Useful for motion blur, glow, translucency and natural gradients.
CheckSoftness should not substitute for a missing core range, otherwise large parts of the subject remain semi-transparent.
- Subtract Softness
Narrows the falloff and makes the transition stricter without changing the selection center.
CheckAn overly hard falloff reveals compression noise and tonal banding.
- Invert
Flips the polarity of the sampled range; useful when it is easier to sample what should become opaque than what should be removed.
CheckAfter Invert, recheck Output B/W: correct geometry with wrong polarity looks like a completely broken key.
- Reset
Clears the sampled luminance range while retaining the rest of the effect setup.
CheckUse Reset after changing the selection strategy instead of endlessly repairing an obsolete range.
MATTE FINESSE · BANK 1
Stabilize density and edge only after sampling
- Pre Filter
Pre-smooths problematic structure so compressed or noisy luminance produces less fragmented keying.
CheckKeep it minimal on clean sources: hair, thin lines and texture disappear first.
- Clean Black
Gently pushes contaminated black/background matte regions toward pure black.
CheckHeavy values erode low-opacity detail and fine edges.
- Clean White
Gently fills gray holes inside the white/foreground matte.
CheckCan close legitimate holes and thicken the foreground.
- Black Clip
Rejects dark-gray contamination more aggressively. The captured neutral value is 0.0.
CheckRaise it after Clean Black and inspect semi-transparent edges in motion.
- White Clip
Normalizes light-gray foreground toward white more aggressively. The capture shows the neutral endpoint at 100.0.
CheckAn overly low White Clip quickly turns soft detail into a solid cutout.
- Blur Radius
Softens the already-built matte and can suppress small chatter.
CheckBlur trades local accuracy for smoother edges; do not use it as the first fix.
- In/Out Ratio
Biases edge treatment relative to the boundary—toward the inside or outside—after blur/finesse.
CheckThis is fine edge compensation, not a full substitute for Shrink/Grow.
MATTE FINESSE · BANK 2
Morphology changes finished alpha geometry
- Operation · Shrink · Grow · Opening · Closing
Shrink/Grow contract or expand the opaque region; Opening helps small white specks, Closing helps small black holes.
CheckChoose the operation for a specific defect, not as a generic quality boost.
- Shape · Circle · Square · Diamond
Shape defines morphology-kernel geometry and is most visible around corners and diagonals.
CheckOrganic edges usually prefer a more neutral shape; compare on hair and diagonals.
- Radius · Iterations
Radius sets the scale of one morphology pass; Iterations repeats it.
CheckRepeated passes quickly destroy thin detail; use the minimum sufficient amount.
GARBAGE MATTE + OUTPUT
Constrain space and inspect the right signal
- Matte Shape · None · Rectangle · Ellipse
Garbage Matte excludes frame regions Luma Keyer should not need to solve. The native menu confirms None, Rectangle and Ellipse.
CheckUse a spatial limiter before aggressive Matte Finesse when the unwanted area is far from the subject.
- Output · Alpha Highlight · Alpha Highlight B/W · Final Composite
B/W shows the matte itself, Alpha Highlight preserves more color context, and Final Composite shows the real result over the lower track.
CheckTune density in B/W, but approve the edge only in Final Composite over both bright and dark backgrounds.
03CORE RANGE ≠ FALLOFF
Fix membership before you polish the boundary.
Most Luma Keyer confusion comes from treating Add Range, Add Softness and Matte Finesse as three strengths of the same operation. They act at different stages.
| Stage | Question it answers | Typical mistake |
|---|---|---|
| Luma Range | Which brightness values fully belong to the selection? | Expanding it to fix a soft edge and accidentally capturing equal-brightness foreground. |
| Softness | How should membership fall off outside the core? | Using a huge falloff to cover brightness values that should have been in the core. |
| Matte Finesse | How should the finished matte be stabilized or repaired? | Trying to repair a fundamentally wrong selection with Clean/Clip/Blur. |
Practical diagnostic: if lowering Clean/Clip/Blur toward neutral reveals the wrong object inside the matte, that is a selection problem, not a cleanup problem.
04FROM SOURCE TO COMPOSITE
Make upstream decisions before downstream repairs.
The workflow is intentionally strict because it makes failures traceable. If the key is wrong, you know whether to revisit luminance membership, spatial constraint, edge cleanup or final compositing.
Build the core range
Sample Eyedropper first; Add/Subtract Luma Range only when actual luminance values are missing or over-selected.
Teaching workflow, not a literal Resolve node graph. The durable rule is upstream before downstream: define luminance membership, then refine matte geometry/density, then judge the real composite.
Related workflows: Qualifier / Windows / Tracker ↗ · node pipeline ↗
05BUILD REPEATABLE KEYS
Four exercises with a visible acceptance condition.
None of these recipes are fixed presets. Their purpose is to teach the order of decisions and a concrete condition for stopping before cleanup destroys the edge.
Isolate a bright product/sign
Build a luminance-only matte without chroma dependence.
PrepareA shot where the target is clearly brighter than its surroundings even if color varies.
- 01
Drag Sample Eyedropper across a representative bright area and enable Invert if the sampled range should become white/opaque.
- 02
In Alpha Highlight B/W refine the core with Add/Subtract Luma Range, then adjust only the falloff with Softness.
- 03
Add minimum Clean Black/White; use Clip only if density is still unstable.
- 04
Check Final Composite over both bright and dark backgrounds.
The target is stable, background does not leak, and soft detail has not turned into a cutout.
Key a dark silhouette
Use luminance polarity instead of a chroma key.
PrepareForeground is clearly darker than the background: a silhouette, window, graphic or practical shadow.
- 01
Sample the dark range and verify polarity in B/W Output.
- 02
Narrow the Range if dark background structures enter the key.
- 03
Use Garbage Matte when unwanted dark objects are spatially separate.
- 04
Inspect the contour in motion; do not treat tracking-like movement by increasing Blur Radius.
The silhouette remains solid without capturing unrelated dark set pieces.
Stabilize a compressed/noisy edge
Reduce chatter without a visible halo.
PrepareThe range is already correct, but the edge chatters because of noise/compression.
- 01
First confirm the issue remains with correct Range/Softness.
- 02
Add a very small Pre Filter.
- 03
If necessary, add minimal Blur Radius and compensate the boundary with In/Out Ratio.
- 04
A/B hair, thin lines and motion blur; back off when structure disappears.
Chatter is reduced without making the contour thick, soft or lagging.
Simplify the key with Garbage Matte
Avoid forcing luminance selection to solve a distant unrelated object.
PrepareThe desired subject and a false brightness match occupy different frame regions.
- 01
Keep the luminance range optimized for the subject.
- 02
Choose Rectangle or Ellipse and constrain the working area.
- 03
Add only enough garbage-matte edge softness to avoid a spatial seam.
- 04
Check motion/tracking needs: a static garbage shape must not drift away from a moving subject.
The false match is excluded spatially without damaging the core luma range.
06CHOOSE THE DIMENSION THAT SEPARATES
Luma Keyer is excellent when luminance is the useful signal—and the wrong tool when it is not.
A cleaner workflow often comes from switching keyers early rather than forcing one-dimensional brightness selection to solve a color problem.
| Tool | What separates pixels | Use it when |
|---|---|---|
| Luma Keyer | Luminance only | Brightness itself isolates highlights, shadows, silhouettes, screens, signs or tonal plates. |
| HSL Keyer ↗ | Adds Hue and Saturation as independent criteria. | When different colors share similar brightness and luminance alone cannot separate them. |
| 3D Keyer ↗ | Stroke-based multidimensional color selection. | For screen keying and complex color families when quick drag sampling is preferable to H/S/L constraints. |
| Alpha Matte Shrink and Grow ↗ | Morphology of an existing alpha without a new selection. | When matte membership is already correct but edge geometry needs Shrink/Grow/Opening/Closing. |
07DIAGNOSE THE STAGE, NOT THE SLIDER
A bad matte usually tells you whether selection, cleanup, space or composite is wrong.
Treat each symptom as evidence. Moving several downstream controls at once may make one frame look better while making the key less understandable and less stable.
01The foreground disappears together with the background
Brightness overlap exceeds Luma Keyer’s discriminating power. Tighten the sample, use Garbage Matte or switch to HSL/3D Keyer; do not compensate with heavy Clean/Clip.
02The edge looks synthetic and too thick
Move Clean/Clip/Blur closer to neutral, recheck Range/Softness and rebuild the matte. Use In/Out Ratio only as a small compensation.
03The matte looks good in B/W but the composite has a halo
Judge the edge in Final Composite over bright and dark backgrounds. Reduce Blur, adjust In/Out Ratio and verify semi-transparent detail was not clipped.
04The key chatters frame to frame
First verify source luminance and sample-range stability. Then use minimal Pre Filter/Blur. If the target moves relative to a garbage shape, solve that spatial/tracking problem separately.
05Everything became “backwards” after Invert
This is polarity, not a new selection. Switch to Alpha Highlight B/W and decide which side should be white/opaque before returning to cleanup.
Playback beats a still
Chatter, edge pumping and garbage-matte drift often disappear in a still. Inspect several seconds around difficult motion.
Check two backgrounds
A bright background exposes dark fringe; a dark one exposes bright fringe. One convenient background can hide a matte error.
Do not confuse luma key with a luma grade
Luma Keyer creates an alpha/compositing decision. If the goal is simply to grade highlights/shadows inside a Color node, Qualifier or tonal grading tools may be simpler.
08FAQ
Practical Luma Keyer questions.
How is Luma Keyer different from HSL Keyer?
It uses luminance only. Blackmagic describes it as HSL Keyer with H and S turned off. That makes it simpler and can be robust on compressed material, but it cannot separate equal-brightness objects by color alone.
When should I use Add Luma Range versus Add Softness?
Range adds brightness values to the fully selected core. Softness only expands the transition around an already selected range.
Why start with Alpha Highlight B/W?
Because B/W separates alpha geometry/density from the attractiveness of the composite. It makes holes, leaks and clipping easier to see. Final approval still happens in Final Composite.
Can heavy Matte Finesse rescue a bad sample?
It can sometimes hide a symptom, but it cannot restore missing discriminating information. If membership is wrong, return to sampling or choose a keyer with the right dimensions.
Does Garbage Matte replace a tracker?
No. Rectangle/Ellipse is a spatial limiter. If the subject moves substantially, the shape must follow the task through an appropriate tracking/roto workflow.
09SOURCES & BOUNDARIES
Current control labels come from native project captures; stable keying behavior is cross-checked against Blackmagic documentation.
The lab is intentionally independent. It demonstrates luminance-range membership, falloff, polarity and simple matte cleanup, but does not claim Resolve’s internal luminance coefficients, sampling accumulation, Matte Finesse implementation, GPU behavior or parameter scale. Matte Finesse Bank 2 is documented as stable Resolve FX Key behavior; the supplied native full-panel capture is showing Bank 1.