How to Use a Green Screen (Chroma Key) on Your Phone
Shot against a green screen? Chroma key gives the cleanest cut-out there is — crisp edges, even around hair and fast motion. Here’s how to key it on your phone, and how to shoot it so the key is easy.
A green screen is still the gold standard for putting yourself somewhere else — it gives the cleanest edges of any technique. ExpoCut keys it on-device: pick the color, and your subject lands on any background you like.
Step 1 — Add the clip and a background
Put a background layer down first
An image, a stock video, or a generative scene — whatever your subject should stand in front of.
Add your green-screen clip on top
It sits above the background, covering it for now.
Open Chroma Key and pick the color
Tap the green (or blue) to key it out. That color turns transparent and the background shows through.
Green clip on top (V2) · background layer below (O1)
Chroma Key
Step 2 — Tune the key
Pick the key color — green by default
Tune Similarity, Smoothness & Spill Suppress
A first key is rarely perfect. Raise Similarity so:
- All the green disappears (push it up until the background is gone), but
- The subject’s edges stay intact (don’t push so far that hair or edges get eaten).
The sweet spot is the smallest amount of keying that fully removes the screen. Add a little Spill Suppress to neutralise any green that lingers on edges.
Chroma key or auto-remove? Use chroma key when you filmed on a green/blue screen — crisper edges. Use automatic background removal when you shot on a normal backdrop.
Shoot it so the key is easy
Most “bad keys” are bad footage. On set:
- Light the screen evenly — no shadows or hot spots on the green.
- Step forward — keep your subject a couple of feet off the screen so green doesn’t spill onto them.
- Don’t wear green (or blue, if it’s a blue screen).
- Avoid motion blur — more light and a steadier shot mean cleaner edges.
Step 3 — Sell it
Match your subject to the new scene with a light grade, and add a touch of background blur for depth. A subject that shares the scene’s color and focus reads as genuinely “there.”
Where to go next
- No green screen? remove the background automatically.
- Build the backdrop: generative backgrounds & shaders.
- Blend subject and scene: color grading on your phone.
Light it flat, stand forward, key the color, and grade to match — that’s a clean green-screen composite, made on a phone.
Frequently asked questions
How do I remove a green screen from a video?
Add your green-screen clip, select it, open Chroma Key, and pick the green as the key color. ExpoCut makes that color transparent so whatever layer you put underneath shows through. Tune the threshold until the edges are clean.
Green screen vs. automatic background removal — which is better?
If you actually filmed on a green/blue screen, chroma key wins — it gives crisper edges, especially around hair and fast movement. If you shot on a normal background, use automatic background removal instead. Both are on the clip's tools.
Why does my key look rough around the edges?
Usually uneven lighting or green spill. Light the screen evenly (no shadows), keep your subject a step or two in front of it so green doesn't bounce onto them, and avoid wearing anything green. Then fine-tune the key threshold.
Key it clean
Drop a green or blue screen and put your subject anywhere. Crisp chroma keying — even around hair and motion — right on your phone.
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