A green-screen workflow uses the background color to help separate the subject, then composites that subject over another image. Good capture makes the separation easier. Keying software cannot reliably recover every hair, transparent object or heavily blurred edge from poor footage.
Plan subject and background separately
Light the screen evenly enough for the intended frame and expose it without clipping. Light the subject for the replacement environment. Choose distance by testing spill, shadows, framing and the available space; there is no universal number of feet that guarantees a clean key.
Keep the subject away from obvious wrinkles or shadows where practical, and check reflective clothing, glass and green objects before committing the scene. Record a short motion test at the actual shutter, codec and frame rate. A static preview can conceal problems that appear when the subject moves.
Understand plate, matte, despill and composite
| Stage | What to inspect |
|---|---|
| Plate | Original screen footage: exposure, focus, wrinkles, spill and motion. |
| Matte | Foreground should remain opaque, background transparent, and fine edges retain appropriate partial transparency. |
| Despill | Remove unwanted screen contamination without stripping legitimate subject colors. |
| Composite | Match perspective, scale, light, contrast, focus and contact with the background. |
Choose the replacement background before lighting the subject
The screen helps separate the subject; it does not make the subject belong in the new scene. Decide the background’s camera height, perspective, light direction and apparent focus before recording. A person photographed with a high, hard key will be difficult to place convincingly inside a room lit softly from a low window.
For a first setup, use a locked camera and a background with a compatible viewpoint. A moving foreground camera needs the replacement environment to respond appropriately, which may require tracking and additional perspective work. Decide whether the final frame includes feet and a floor. A seated waist-up presenter avoids the contact shadows and floor transitions required by a full-body walking shot.
Build a screen setup that stays consistent
Cover the whole movement, not just the starting pose
Frame the largest planned gesture and the edges of moving hair or clothing. The screen needs to cover the area behind that movement. Smooth major wrinkles and remove distracting objects from the working region. A garbage matte can exclude an unused corner later, but it cannot recover a hand that moves beyond the available screen into a complex background.
Light the screen and person for different jobs
Aim for a consistent, unclipped screen color across the region you will key. Give the subject lighting that matches the destination scene. Increasing the screen brightness until it looks luminous can create more reflected color on the subject and reduce useful separation. Check the actual recorded image, not just how the fabric looks to your eye.
Increase subject-to-screen separation where the space permits, and adjust positions to reduce shadows and colored reflections. There is no universal distance that works for every room, lens and framing. Inspect pale clothing, skin, shiny objects and hair for spill. Use properly supported lighting and backdrop equipment, keeping the performer’s movement and exit route clear.
Choose green or blue around the subject
Use a screen color that can be separated from the important foreground colors. A green garment may disappear into a green key; a blue garment creates the analogous problem against blue. Reflective and transparent materials can show the screen through or around them, making either choice more demanding. Do not assume green always produces easier spill removal, or that blue is suitable because a foreground object is blue.
Record a real-motion test before the full performance
Test the actual wardrobe, hair and props. Include a turn, a hand crossing the body and the fastest planned action. View a trial key over the intended background. This catches a problem that a neatly posed still misses: a sharp subject center can coexist with unstable hair, translucent fingers or a badly blurred edge.
Set exposure and white balance consistently so the screen does not drift in appearance during the take. Choose the shutter for the motion you intend to deliver. A shorter exposure can reduce motion blur but changes how movement looks and may require more light. It is not a universal “highest shutter speed” setting. Test the camera’s actual codec and recording mode instead of assuming the highest pixel count guarantees the best key.
Understand what the matte is telling you
The matte is a grayscale description of transparency. In a conventional alpha display, white means opaque, black means transparent and gray represents partial transparency. Hair, glass and motion-blurred edges may legitimately contain gray. Forcing every gray pixel to black or white can destroy those transitions.
Inspect the matte and composite separately. A clean silhouette over black can still show a green fringe over the final background. Conversely, an attractive composite against a dark background can conceal unwanted transparency in clothing. Try contrasting diagnostic backgrounds, then return to the real destination image.
Use the right repair for the right problem
- Garbage matte: exclude unused surroundings so the keyer does not have to solve an irrelevant dark corner or stand. Keep the mask clear of the entire subject movement.
- Core or hold-out protection: preserve a foreground area that the key has made transparent, such as a logo whose color resembles the screen. Follow the area through the shot.
- Matte refinement: improve the boundary and opacity without casually erasing fine detail.
- Despill: reduce unwanted screen-colored contamination on the retained subject. This corrects color; it is not the same operation as making the background transparent.
Adobe documents garbage and hold-out mattes, and separately documents Keylight, Key Cleaner and Advanced Spill Suppressor. The distinction between extraction, edge cleanup and spill control is useful in other compositing workflows too, though their controls have different names.
Finish the composite and choose the correct export
After extracting the subject, compare the foreground and background for contrast, color, light direction, scale, focus and grain. Check contact shadows when a person stands on a visible floor. A technically clean key can still look pasted on if the photography does not agree.
If delivering a cutout, choose a format and codec that actually support alpha and confirm the alpha interpretation in the receiving application. An ordinary viewing copy may show a solid background even when a separate cutout exists. If delivering the completed scene, render the foreground and background together and inspect the full moving export.
The downloadable synthetic-key.comp is useful for studying a simple node connection: generated source, Delta Keyer and composite. Its flat-color ellipse does not contain the uneven lighting, hair, reflections or motion of camera footage. Keep that distinction when comparing the lab below with your own test.
A documented Resolve/Fusion starting workflow
Blackmagic’s Resolve 18 Fusion training guide teaches Delta Keyer as a screen-keying tool. The guide is versioned; the current Studio test described below is separate evidence.
- Confirm input interpretation and use the foreground clip as the source.
- Add a Delta Keyer in the Fusion workflow and sample a representative screen area.
- View the matte as well as the composite. Limit the working region where appropriate, keeping the full subject movement.
- Refine background and foreground separation without crushing all soft edge detail.
- Control spill and merge over the intended background, then inspect the whole moving shot.
Do not copy a threshold value from an unrelated shot. The required settings depend on the screen, lighting, compression and subject.
Current-version test: a synthetic still
On October 30, 2026, we built and rendered a simple node test in DaVinci Resolve Studio 21.1.1.10 on macOS. Fusion generated an orange ellipse over a flat green background. Delta Keyer removed that background, and a Merge placed the cutout over blue. The exported alpha measured 0 at a background sample and 255 at the opaque subject center. The saved composition was also reimported.
Download the Fusion composition, instructions and rendered stills (ZIP). The project uses generated nodes and has no external media dependency. Its screen RGB inputs are 0.05, 0.7 and 0.08, matched by the keyer’s background inputs; these values describe this synthetic recipe only.
Failure and repair checks
| Problem | First check | Likely limit |
|---|---|---|
| Uneven screen | Lighting, wrinkles, shadows and a representative sample. | Aggressive thresholds can erase subject detail. |
| Green edge | Subject/screen separation, reflective surfaces and despill. | Removing green globally can damage legitimate colors. |
| Hair disappears | Matte refinement and source sharpness. | Fine partly transparent detail cannot be treated as a hard cutout. |
| Motion looks cut out | Blur and temporal consistency through the whole shot. | A clean single frame does not establish a good moving key. |
| Composite looks pasted on | Perspective, lighting, contact, focus and grain. | A technically clean matte does not solve mismatched photography. |
No original green-screen shoot or camera-recorded sample clip is claimed here. The CGI breakdown supplies an original conceptual illustration; day-for-night explains why convincing finishing also depends on capture decisions.
Keying can be demanding on the editing system. Use the editing-laptop guide as a starting list of buying considerations, then verify current model specifications, software requirements and prices before purchasing. Test the actual codec and composite instead of inferring performance from a laptop’s marketing label.
