Where should you sample an uneven green screen?
Start with a midtone on the actual screen, away from the subject and shiny spots. Hold tolerance steady and check the darkest and brightest areas in the matte. If either remains, try another clean sample or split the backdrop into separate keys.
A row passes if all pixels in the backdrop patches at (30, 40), (150, 40) and (270, 40) are removed and all pixels in the subject patch at (150, 120) remain, using 20 × 20 pixel patches.
| Test date | Tool and version | Same source or frame | Setting changed | Result |
|---|---|---|---|---|
| 2026-11-11 | Node 24.22.1 | uneven-green-screen-source.png, still | Shadow (35, 25) | Fail. The highlight patch retained 400 backdrop pixels. |
| 2026-11-11 | Node 24.22.1 | uneven-green-screen-source.png, still | Midtone (160, 25) | Pass. All backdrop patches cleared and the subject patch retained 400 pixels. |
| 2026-11-11 | Node 24.22.1 | uneven-green-screen-source.png, still | Highlight (275, 25) | Fail. The shadow patch retained 400 backdrop pixels. |
Source file uneven-green-screen-source.png · Download the original PNG
Download the parameter sheet and reproduction script.
Why the middle sample worked
The test plate has three uniform green bands. Their green-channel values are 100, 124 and 148, with red and blue fixed across the screen. The script removes a pixel if each RGB channel lies within 26 levels of the sampled color. The middle sample is 24 levels away from either extreme, so it covers all three bands. The shadow and highlight samples are 48 levels apart, so either extreme leaves the opposite band in the matte. The warm subject remained outside the threshold in all three runs.
We changed only the sample coordinates. Each failed row left the entire opposite patch visible, while the middle patch cleared in every run. The subject check stayed constant and showed that the improvement on this plate came from reaching more backdrop pixels. The downloadable script and parameter sheet use the same coordinates for every row.
How to choose a point on footage
Pick an unobstructed patch near the middle of the screen's brightness range. Inspect a shadow, a bright patch and a piece of the subject you want to keep in the matte view. If cleaning the screen eats into the subject, mask the affected region and tune its key separately. Check more than one frame when the subject or lighting moves. This synthetic plate varies only the green channel and does not measure spill, noise or motion.
For the eyedropper workflow and a gradient example, see Sleek's sampling instructions and Online PNG Tools' background remover.