Purpose
A busy image hides broad patches. A single grey makes them easier to see. Use this when a screen looks stained, darker in a corner, or slightly warm on one side.
Preparation
- Sit centred, at your usual distance.
- Keep room light even. A window on one side can look like a panel stain.
- Clean fingerprints with a dry cloth. Do not press.
- Note the brightness and picture mode, but you do not have to change them.
The signal levels
| Label | RGB | Hex |
|---|---|---|
| 5% grey | 13 | #0D0D0D |
| 10% grey | 26 | #1A1A1A |
| 25% grey | 64 | #404040 |
| 50% grey | 128 | #808080 |
| 75% grey | 191 | #BFBFBF |
| 90% grey | 230 | #E6E6E6 |
Each value is Math.round(255 × percent / 100). It is not a measurement of the backlight.
What to look for
Broad clouds, corners that fall off, vertical bands, or a tint that covers part of the field. “Run grey sequence” walks 5%, 10%, 25%, 50%, white and black.
Common false positives
Viewing angle on IPS, grease, a screen protector, and light falling on the glass. A patch that moves when you tilt your head is a different observation from a patch that stays while you sit still.
Limitations
This is not a luminance map and not a dirty-screen score. Two people can describe the same mild cloud differently. Your notes are the record.
Questions
Which grey should I use?
Start with 50% grey, RGB 128 (#808080). Then try 25%, 10% and 5% if you are looking for clouding in the shadows.
Does 50% mean half brightness?
No. It means half of the 8-bit code range, rounded. The panel’s brightness setting, gamma and tone curve change how light that code looks.
The patch moves when I tilt my head. What then?
It could be viewing angle or coating, which is common on IPS panels. Note that it moves. A fixed stain tends to stay when you sit centred.
Can I judge this from a photo?
A camera changes exposure and invents texture. Look with your eyes. If you need a record, photograph the panel from outside the browser and say that in your notes.