RESOLVE FX · LIGHT · STUDIO
Aperture
Diffraction.
Do not start with glow.
Start with the aperture that could have made it.
Aperture Diffraction turns selected bright regions into a virtual-aperture response: isolate emitters, define iris geometry, shape the resulting diffraction, then composite it back. Thinking in those four stages is what keeps a starburst optical instead of decorative.
Emitter map
6 Iris Shapes
Diffraction → Final
The lab is an independent optical teaching approximation. It demonstrates stage order and relationships; it does not reproduce Blackmagic’s private diffraction kernel or parameter scales.
Aperture Controls
Diffraction + Compositing
Independent teaching approximation. The lab demonstrates stage order, emitter gating, polygon symmetry, anisotropy, chroma separation and final mixing. It does not reproduce Blackmagic’s private diffraction kernel, source-isolation math, exact parameter scales, quality modes or GPU implementation.
Five native Inspector captures + an independent diffraction teaching model.
Source · Iris · Diffraction · Composite01SOURCE BEFORE STYLE
The effect becomes predictable when emitter selection, aperture geometry and final mix stay separate.
Blackmagic describes the effect as diffraction on virtual aperture blades applied to scene highlights. The practical implication is simple: every downstream control assumes the emitter map is already meaningful.
Decide what emits before shaping the optics
Source Regions is the upstream gate. Brightness/Gamma/Smooth, Color Mode/Color Filter and morphology define the emitter map. If a white wall qualifies instead of the lamp, no attractive Iris Shape can make the result physically convincing.
Aperture geometry and diffraction result are different stages
Iris Shape, Aperture Size, Blade Curvature, Rotation, H vs V Ratio and Angle describe the virtual aperture. Result Gamma/Scale act on the already-computed diffraction response. Keep the cause geometry separate from result shaping.
Final mix should not hide upstream mistakes
Brightness, Colorize and Blend make sense after a clean emitter map and stable optical geometry. If rays appear in the wrong places or point the wrong way, Global Blend only makes the error quieter; it does not repair it.
Stable optical behavior reference: Blackmagic Design · Aperture Diffraction ↗
02THE ACTUAL RESOLVE 21 PANEL
Five native captures anchor the guide to the current interface.
The full panel records the main control hierarchy, while dedicated captures confirm the Input Alpha, Quality and Iris Shape menus plus Compositing Controls. Source Regions is collapsed in the supplied full-panel capture, so its stable behavior is documented from Blackmagic reference material rather than invented pixels.
OUTPUT / ROUTING
Diagnostic views, Input Alpha and Quality
- Source Regions · Diffraction Alone · Final Result
The three top buttons expose source isolation, the generated diffraction pattern and the final composite. They are not different algorithms; they are three views into stages of the same effect.
CheckTune threshold in Source Regions, geometry in Diffraction Alone, and approve only in Final Result.
- Input Alpha
Masks The Source Regions constrains auto-detected emitters with embedded alpha. Is Used For Compositing keeps source detection but applies alpha at compositing. Is The Source Of The Glow makes embedded alpha itself the emitter map.
CheckDo not confuse embedded Input Alpha with a separate Effect Mask: alpha changes internal Light FX routing, while Effect Mask only gates node contribution.
- Quality
Full is for final detail evaluation, Half (Faster) speeds interactive tuning, and Quarter (Fast) is useful for finding the broad shape on a heavy timeline.
CheckReturn to Full before render/QC; a performance mode should not become a hidden part of the look.
SOURCE REGIONS
Build a clean emitter map first
- Color Mode
Source analysis can preserve color in qualifying highlights or run faster as grayscale brightness analysis. Color mode is useful when emitter chroma is part of the separation.
CheckIf color does not improve separation, grayscale is usually easier to reason about and cheaper to process.
- Brightness
The brightness threshold decides which pixels enter the source region and are allowed to generate diffraction. It is the main upstream control preventing ordinary bright surfaces from glowing.
CheckJudge it in Source Regions, not Final Result; downstream Brightness/Blend can easily hide a bad threshold.
- Gamma · Smooth
Gamma reshapes density inside the qualified regions; Smooth suppresses fine texture so it is not replicated into the diffraction pattern.
CheckToo much Smooth turns a point emitter into a broad shapeless region and changes the optical response.
- Color Filter · Eyedropper
Color Filter can constrain the emitter map to a selected hue/color family, with the eyedropper sampling a reference from the image. It is useful when bright sources of different colors sit next to each other.
CheckCheck the sample across frames; a moving or color-changing source can fall outside an overly narrow filter.
- Operation · Shrink · Grow · Opening · Closing
Morphology acts on the existing source matte: Shrink contracts it, Grow expands it, Opening helps remove small white specks, and Closing fills small holes.
CheckThis is repair geometry, not a new detector. If the wrong pixels qualify, return to Brightness/Color Filter instead of pushing morphology.
APERTURE CONTROLS
Describe the virtual aperture before adding intensity
- Iris Shape
Triangle, Square, Pentagon, Hexagon, Heptagon and Octagon define polygonal symmetry of the virtual aperture and change the directional structure of the starburst.
CheckChoose shape before Result Gamma/Scale; intensity should not compensate for unsuitable geometry.
- Preview Shape · Preview Diffraction Pattern
Preview Shape displays the aperture directly; Preview Diffraction Pattern lets you inspect the optical response without the composite. This is a fast way to separate cause from result.
CheckIf geometry already looks wrong in preview, do not move on to Colorize/Blend; fix the aperture first.
- Aperture Size · Blade Curvature
Aperture Size changes the character and scale of the virtual-aperture response; Blade Curvature softens/reshapes the arms relative to a hard polygon.
CheckDo not confuse Aperture Size with Result Scale: the first belongs to the optics stage, the second reshapes the already-computed result.
- Rotation · H vs V Ratio · Angle
Rotation turns the optical pattern, H vs V Ratio introduces horizontal/vertical anisotropy for anamorphic-like structure, and Angle sets the orientation of that stretch.
CheckFor believable optics, orientation motion should follow camera/lens logic; arbitrary animation quickly reads as motion graphics.
- Chroma Shift
Chroma Shift separates color components in the diffraction response and adds wavelength-like color separation around the rays.
CheckLarge values quickly become stylized. Start at zero and add only as much separation as survives motion/QC.
DIFFRACTION CONTROLS
Shape the already-computed optical response
- Result Gamma
Result Gamma redistributes energy inside the diffraction result, especially between bright arms and weaker light between them.
CheckInspect Diffraction Alone; source contrast in Final Result can hide an overly aggressive gamma setting.
- Result Scale
Result Scale changes the scale/prominence of the computed pattern after aperture geometry. It moves between a more diffuse response and a clearer star-like structure without changing the polygon shape itself.
CheckIf the result needs extreme scaling, recheck Aperture Size; the problem may be one stage upstream.
COMPOSITING CONTROLS
Only now set energy and art-directed color
- Normalize brightness
Normalize brightness stabilizes overall diffraction level as emitter strength/size changes, helping the result vary less across frames and sources.
CheckIt is not a substitute for clean Source Regions; normalization can stabilize a wrongly selected emitter, but it remains wrong.
- Brightness · Colorize · Color
Brightness sets the energy of the finished diffraction layer. Colorize controls the amount of art-directed tint and Color chooses the hue. These controls should change presentation, not repair pattern shape.
CheckJudge neutral color first, then add Colorize. This makes it easier to see whether tint is hiding bad source/geometry choices.
- Global Blend · Blend
Blend is the final dry/wet for the fully computed FX. It preserves internal source/geometry decisions and changes only the amount of the finished result in the frame.
CheckIf the full effect is structurally correct but too visible, lower Blend. If ray placement/shape is wrong, fix upstream.
03THREE ALPHA ROLES, THREE OUTPUT VIEWS
Input Alpha changes routing; output views change what you inspect.
This distinction became especially important once Resolve FX Light gained explicit glow-from-alpha behavior. A prepared alpha can constrain source detection, wait until compositing, or replace automatic emitter detection altogether.
| Input Alpha mode | What alpha does | Best diagnostic |
|---|---|---|
| Masks The Source Regions | Alpha gates where automatically detected bright regions may become emitters. | Source Regions |
| Is Used For Compositing | Emitter detection remains source-driven; alpha participates when the generated result is composited. | Final Result |
| Is The Source Of The Glow | Embedded alpha becomes the emitter map itself—ideal for prepared Fusion/VFX mattes. | Source Regions → Diffraction Alone |
Do not confuse these modes with an Effect Mask. Input Alpha is embedded in the RGBA image and changes the internal Light FX routing; an Effect Mask is an external coverage gate for where the node contributes.
04FROM EMITTERS TO FINAL MIX
Build upstream decisions before downstream polish.
A strict optical order makes failures traceable. If something looks wrong, the failure can be assigned to source selection, aperture cause, diffraction-result shaping or final presentation instead of random slider hunting.
Build Source Regions
Use Input Alpha routing plus Brightness/Gamma/Smooth/Color Filter until the emitter map contains only intended light sources.
Teaching signal flow, not a literal Resolve node graph. The durable rule is source before optics, optics before result shaping, and final mix last.
Related workflows: Color node pipeline ↗ · Fusion Aperture Diffraction ↗
05BUILD REPEATABLE OPTICAL LOOKS
Four exercises with an acceptance condition—not magic presets.
The values depend on shot resolution, exposure, source size and intended optics. The useful part of a recipe is the order of decisions and the condition for stopping.
Night headlights without making the whole frame glow
Create local starbursts only from genuine point-like sources.
PrepareA night shot with headlights/lamps plus bright but non-emissive surfaces.
- 01
Open Source Regions and raise Brightness until walls/road markings leave the emitter map.
- 02
Choose Hexagon or Square and inspect Diffraction Alone with neutral Result Gamma/Scale.
- 03
In Final Result enable Normalize brightness, set Brightness, and only then reduce Blend if needed.
Each physical source produces a readable pattern while ordinary white image detail stays quiet.
Prepared alpha as the emitter map
Use a VFX/Fusion alpha instead of automatic RGB thresholding.
PrepareRGBA with a prepared alpha whose white regions mark only the intended emitters.
- 01
Set Input Alpha = Is The Source Of The Glow and inspect Source Regions.
- 02
Keep the source stage simple: alpha already defines the emitters, so do not rediscover them with aggressive thresholding.
- 03
Tune optical geometry in Diffraction Alone, then return to Final Result for compositing.
Diffraction deterministically follows the prepared matte instead of random bright RGB pixels.
Anamorphic-like horizontal diffraction
Build a stretched optical response without turning the effect into arbitrary glow.
PrepareA contrasty point source or sign where effect orientation is easy to read.
- 01
Start from clean Source Regions and one readable Iris Shape.
- 02
Adjust H vs V Ratio, then Angle/Rotation while viewing Diffraction Alone.
- 03
Add a small Chroma Shift only after geometry, then return to Final Result and Blend.
The stretch reads as coherent optical geometry; chroma remains a secondary accent rather than the main effect.
A broad bright region as optical bloom
Show that Aperture Diffraction is useful beyond sharp starbursts.
PrepareA window, hazy sun, or large practical light with a broad bright region.
- 01
Tune Source Regions so the emitter has a stable shape without fine noisy texture.
- 02
Use Aperture Size/Blade Curvature and Result Scale for a more diffuse response.
- 03
Compare against normal Glow; stop if polygon arms become distracting for the shot.
The result is a structured optical bloom still tied to virtual-aperture behavior without reading as a hard star.
06CHOOSE THE LIGHT MODEL
Use Aperture Diffraction when aperture-driven structure is part of the look.
Many overbuilt Light FX setups begin by choosing the most complex plugin instead of the simplest light model that matches the visual problem.
| Tool | Primary visual model | Use it when |
|---|---|---|
| Aperture Diffraction | Virtual aperture → structured diffraction | The shot needs starburst/polygon-driven optical structure tied to selected highlights. |
| Glow ↗ | Soft spread / bloom | When you want controllable soft glow without strong polygon/starburst geometry. |
| Lens Flare ↗ | Multi-element flare system | When you need a complex flare with presets and separate ghost/glare elements rather than one diffraction response. |
| Light Rays ↗ | Directional rays from bright regions | When the goal is volumetric/directional beams rather than virtual-aperture diffraction. |
07DIAGNOSE THE STAGE, NOT THE PRETTINESS
A broken starburst usually points to a specific stage.
Use Source Regions and Diffraction Alone as diagnostic instruments, not presentation modes. They remove visual context precisely so you can tell whether the source or the optical response is wrong.
01Diffraction appears on almost every bright detail.
Return to Source Regions. Raise Brightness, reduce excessive Smooth/Grow, and use Color Filter if needed. Do not treat this with Global Blend.
02The starburst looks good but ignores the prepared VFX matte.
Check embedded alpha upstream and Input Alpha. A prepared emitter map requires Is The Source Of The Glow; Effect Mask is a different routing role.
03The pattern looks like generic blur/glow with no readable optics.
Open Diffraction Alone. Return Result Gamma/Scale near neutral, choose Iris Shape, then tune Aperture Size/Blade Curvature until the structure reads clearly.
04The horizontal streak appears randomly rotated.
Separate Rotation from anisotropy Angle. Set H vs V Ratio first, then orientation; inspect camera motion if the parameters are animated.
05Colored fringes look like a digital RGB split.
Return Chroma Shift to zero, establish believable monochrome geometry, then add only a small amount back.
06Intensity jumps as highlight size changes across frames.
Check Source Regions stability and try Normalize brightness. If the emitter map itself flickers, normalization cannot replace correct threshold/tracking upstream.
07The preview is fast but final detail differs.
Check Quality. Half/Quarter are for speed; return to Full before QC/render and reevaluate fine rays/texture.
08FAQ
Practical Aperture Diffraction questions.
How is Aperture Diffraction different from Glow?
Glow primarily models soft light spread. Aperture Diffraction derives the response from a virtual aperture, producing polygon/starburst structure tied to Iris Shape, blades and diffraction. On broad bright regions it can also resemble bloom, but its underlying structure is different.
Which Iris Shape is “correct”?
There is no universally correct shape. It is an art-directed optical assumption: choose geometry consistent with the intended lens/camera and shot design. Hexagon is a useful neutral starting point, not a universal truth.
When should I use Is The Source Of The Glow?
Use it when an emitter matte has already been prepared upstream—for example in Fusion or a VFX pipeline—and you want embedded alpha to directly define where diffraction is generated instead of automatic highlight detection.
What should I tune first: Brightness or Aperture Size?
Start with Source Regions, then aperture geometry, then Result Gamma/Scale, and only then Compositing Brightness. Otherwise intensity hides selection/geometry problems.
Can it create an anamorphic-like look?
Yes. H vs V Ratio creates anisotropy, Angle/Rotation set orientation, and a restrained Chroma Shift adds optical color separation. It is an art-directed optical behavior, not a physical model of a specific lens.
Why use Diffraction Alone if Final Result exists?
Because the source image and its contrast can hide the pattern. Diffraction Alone makes Iris Shape, Aperture Size, Blade Curvature, Result Gamma/Scale and Chroma Shift easier to judge directly.
Why is the effect computationally heavy?
It builds a spatial diffraction response around selected emitters and provides separate Quality modes. Use Half/Quarter while finding the look, but judge final detail at Full.
09SOURCES & BOUNDARIES
Current UI labels come from native captures; optical and alpha-routing behavior is cross-checked against Blackmagic documentation.
The supplied full-panel capture has Source Regions collapsed. Therefore the article does not pretend to show an expanded current Resolve 21 Source Regions screenshot. Its control semantics are treated as documented stable behavior, while the five supplied images remain the UI evidence for the current panel, Input Alpha, Quality, Iris Shape and Compositing Controls.