Green screen
Display a pure green screen to isolate green sub-pixel defects and check color uniformity. The most visible channel for pixel defect detection.
The human eye is most sensitive to green light, which is why green sub-pixel defects are the easiest to spot — and why green is the most-tested sub-pixel channel in any panel inspection.
What a green screen isolates
A pure green at #00FF00 drives only the green sub-pixels at maximum while leaving red and blue completely off. Because the human eye is most sensitive to green wavelengths (peaking around 555nm), green sub-pixel defects are visually the most obvious — a single dead green sub-pixel can be visible from normal viewing distance where a dead red or blue sub-pixel would require close inspection.
This biological fact also explains why green is used as the luminance channel in most image sensors, video codecs, and Bayer camera filter arrays. Panel manufacturers calibrate green sub-pixel brightness with extra care because any defect is immediately obvious to viewers.
Green sub-pixel isolation
Stress only the green sub-pixel channel. Defects in green sub-pixels appear as dark dots against the bright green field — the most visible defect class thanks to human eye sensitivity.
Color uniformity check
Green is the dominant luminance channel. Any brightness variation across the panel is most visible against a green field — perfect for checking uniformity of edge-lit and full-array LCDs.
Green-screen photography
Fullscreen green serves as an impromptu chroma-key backdrop for green-screen photography and video — useful when a dedicated green screen isn't available.
Sub-pixel sensitivity by color (human eye)
The eye's sensitivity to each sub-pixel color determines how visible defects are and how much brightness each channel contributes to perceived luminance. Green dominates both — it's both the most visible defect color and the largest contributor to perceived brightness.
| Sub-pixel | Eye sensitivity | Luminance contribution | Defect visibility | Typical pixel layout |
|---|---|---|---|---|
| Red | Low (~30% of green) | ~30% of Y | Visible but subtle | 1 sub-pixel per pixel |
| Green | Highest (reference) | ~59% of Y | Most visible — single dot from distance | 1–2 sub-pixels per pixel (RGBW) |
| Blue | Low (~10% of green) | ~11% of Y | Subtle, requires close inspection | 1 sub-pixel per pixel |
How to inspect green sub-pixels and uniformity
- 1
Set room to moderate, even ambient light
Green defects are visible enough that you don't need a dark room — normal indoor lighting is fine. Avoid uneven lighting (e.g. a window on one side) that could create false uniformity impressions.
- 2
Display green fullscreen at 100% brightness
Click the green block above to enter fullscreen. Set monitor brightness to 100% to maximize defect contrast and uniformity visibility.
- 3
Scan for dots, then step back for uniformity
Get close (30cm) and scan a 4×4 grid for dot defects. Then step back to normal viewing distance and look for darker or brighter patches — these are uniformity variations in the green channel.
- 4
Cross-check with red and blue
If you see a uniformity patch on green, switch to red and blue fullscreen. If the patch appears on all three, it's a backlight/luminance issue. If it appears only on green, it's a green-channel-specific uniformity problem — rarer but more serious.
Why green dominates display engineering
The human eye's peak sensitivity sits in the green part of the spectrum — a fact that shapes display engineering from sub-pixel layout to color space encoding. The sRGB color space allocates 59% of the luminance signal (Y) to the green channel, versus 30% to red and 11% to blue. This is why a dead green sub-pixel is more visually disruptive than a dead red or blue one — and why panel manufacturers bin green sub-pixels with tighter tolerances.
Green's dominance also explains why some panels use RGBW (red-green-blue-white) pixel structures — adding a white sub-pixel boosts brightness without taxing the color sub-pixels, but at the cost of color saturation. If you own an RGBW panel (common on some LG IPS TVs), the green screen will reveal whether the white sub-pixels are uniform — patchy brightness on green typically indicates white sub-pixel variation.
For chroma-key (green-screen) use, a fullscreen #00FF00 isn't a perfect substitute for a proper green-screen backdrop — most keying software expects a slightly different green (often #00B140 for broadcast) and even illumination. But for impromptu use (a quick product shot, a video call background replacement), the green screen at 60–80% brightness works as a serviceable key. For background on color science and gamma curves that affect green sub-pixel behavior, see the [color gamut test](/color-gamut-test) and our [color depth guide](/blog/color-depth-explained).
Practical tips for green sub-pixel testing
- Defects visible on green from normal viewing distance are immediate return candidates — green sub-pixel health is the highest bar.
- If your panel looks slightly uneven on green but uniform on red and blue, suspect the green channel's white-balance calibration rather than hardware defects.
- For green-screen chroma keying, set monitor brightness to 60–80% — 100% can blow out highlights and create uneven key edges.
- When buying a used monitor, ask the seller to display green fullscreen for 60 seconds — it's the fastest way to surface uniformity issues.
- Avoid the common mistake of testing only green for uniformity — always cross-check with white and gray to confirm the issue is green-specific.
Green screen — common questions
Pair the green screen with these tests
Red Screen
Isolates the red sub-pixel channel and is the primary OLED burn-in diagnostic pattern.
Blue Screen
Isolates the blue sub-pixel channel — completes the primary-color trio.
Uniformity Test
Multi-zone brightness and color uniformity measurement across the panel.
Color Accuracy Test
Measures ΔE color deviation across the full sRGB and DCI-P3 gamut.
Continue your display inspection
The green screen isolates the most visible sub-pixel channel and reveals uniformity issues. Open the full toolset to verify every channel and complete your pixel inspection.