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Chroma Key Diagnostics

Green Screen Lighting & Keying Test

A green screen only works if it is lit evenly. This measures how uniform your screen actually is across nine zones, finds the dominant key colour, flags shadows and hotspots, and shows you a live key so you can see exactly where the edge breaks before you go live.

Camera off

Step 1

Choose a View

The uniformity map divides your frame into nine zones and shades each by how far its brightness sits from the frame average. Even shading means even lighting.

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Step 2

Measurements

Screen Uniformity

  • Uniformity Score:—
  • Brightest Zone:—
  • Darkest Zone:—
  • Spread:—

Key Colour

  • Detected Hue:—
  • Saturation:—
  • Screen Coverage:—
  • Edge Cleanliness:—

Problems Found

  • Shadow Zones:—
  • Hotspots:—
  • Colour Spill:—
  • Overall:—

Notes

Why evenness matters more than the screen itself

Chroma keying works by removing every pixel within a tolerance range of one colour. If your screen is brightly lit on one side and shadowed on the other, those are effectively two different colours, and no single tolerance setting removes both cleanly. Widening the tolerance until the dark corner keys out starts eating into your hair and clothing; narrowing it until you look clean leaves a grey patch floating behind you.

This is why an expensive screen lit badly performs worse than a cheap sheet lit evenly. The fabric is rarely the limiting factor — the lighting almost always is.

Fixing what this test finds

Low uniformity scoreUse two lights aimed at the screen from opposite sides at roughly 45 degrees, rather than one light in the middle. The goal is flat, boring illumination across the whole surface.
Shadow zonesUsually your own shadow falling on the screen. Move further forward, away from the screen — a metre of separation removes most of it.
HotspotsA light too close or aimed directly at one area. Move it back, or bounce it off a wall to spread it.
Colour spillGreen light bouncing off the screen onto you, giving your edges a green rim. Increase your distance from the screen and light yourself separately from the screen.
Poor edge cleanlinessOften wrinkles in the fabric creating micro-shadows. Steam, iron, or stretch the screen taut.

Scope of this test

The uniformity and hue figures here are measured from your live feed, and the live key uses the same class of colour-distance approach that conferencing and streaming software applies. It is a diagnostic preview, not a production keyer — it will not match the exact output of any specific application, because each uses its own proprietary tuning.

What it is genuinely reliable for is the thing that actually determines your result: whether your screen is lit evenly enough to key cleanly at all. That answer is the same regardless of which software you use afterwards.

Benchmark Reference

Verdict Thresholds at a Glance

VerdictUniformityOther conditions
Ready to key≥ 75/100Zero shadow zones and spill ≤ 3% of frame.
Usable50 – 74/100Improvements available but workable.
Will key poorly< 50/100Fix lighting before relying on this screen.

These are this tool's own real verdict thresholds, computed from your nine-zone luminance map live.

Step-by-Step

How to Run the Test

  1. Click "Start" and allow camera access when prompted, with your green screen filling the frame.
  2. Step out of frame briefly so the tool can map the screen's uniformity without your body blocking zones.
  3. Read your uniformity score, shadow zones, and spill percentage.
  4. Switch to the live key view to preview roughly how a real chroma key would look with your current lighting.

Common Issues

Fixing What This Test Finds

Low uniformity scoreUse two lights aimed at the screen from opposite sides at roughly 45 degrees, rather than one light in the middle. The goal is flat, boring illumination across the whole surface.
Shadow zonesUsually your own shadow falling on the screen. Move further forward, away from the screen — a metre of separation removes most of it.
HotspotsA light too close or aimed directly at one area. Move it back, or bounce it off a wall to spread it.
Colour spillGreen light bouncing off the screen onto you, giving your edges a green rim. Increase your distance from the screen and light yourself separately from the screen.
Poor edge cleanlinessOften wrinkles in the fabric creating micro-shadows. Steam, iron, or stretch the screen taut.
Camera access blockedClick the camera icon in your browser's address bar to confirm this site is allowed, or check your OS's camera privacy settings.

Common Questions

Frequently Asked Questions

How do I know if my green screen is lit evenly?
The uniformity map divides your frame into nine zones and shades each by how far its brightness sits from the average. Even shading means even lighting, which is what determines whether keying works at all.
Why does my green screen key badly?
Almost always uneven lighting rather than the fabric. A brightly lit side and a shadowed side are effectively two different colours, and no single tolerance setting removes both cleanly.
What is green screen spill?
Green light bouncing off the screen onto you, giving your edges a coloured rim. Increase the distance between you and the screen, and light yourself separately from it.
Do I need an expensive green screen?
No. A cheap sheet lit evenly outperforms an expensive screen lit badly. Wrinkles matter though — steam or stretch the fabric, since creases create micro-shadows that break the key.
Will my key look exactly like this preview in OBS or Zoom?
Not exactly — this uses the same class of colour-distance approach real keyers use, but each application tunes its own algorithm differently. It is reliable for telling you whether your lighting is even enough to key well at all, which is the same regardless of which software you use.
Can I use a blue screen instead of green?
Yes, physically either works, though this tool is tuned to detect and analyze green specifically. Green is more common because most cameras' sensors are more sensitive to green light, giving a cleaner signal to key from.