Monitor Test — Gradients, Banding and Backlight Bleed
Beyond dead pixels, monitors fail in subtler ways: banding in gradients, bright patches at the edges (backlight bleed), colour shifting from one corner to another, and crushed blacks. This page shows the patterns that make each of those visible on your actual screen.
Quick answer: Cycle through the patterns full screen: a smooth gradient should have no visible steps, a dark grey screen should not show large bright patches at the edges, and a flat grey field should look evenly grey across the whole panel. Judgments about bleed and uniformity are easiest in a dark room, straight on, at normal brightness.
| Patterns included | Linear gradient, grey steps, flat grey, black, white, colour fields, checkerboard and a cross-hatch sharpness grid |
|---|---|
| Backlight bleed | Bright patches along edges on a black screen — common on IPS and some VA panels, worse in a dark room |
| Banding | Visible steps in a gradient that should be smooth — usually the panel or a compression/bit-depth setting, not the test |
| Fair testing | Reset picture settings to defaults, disable dynamic contrast and energy saving, and let the screen warm up for 30 minutes |
Reading each pattern
The linear gradient exposes banding and posterisation — steps that indicate 6-bit processing or heavy compression. The grey steps show whether very dark tones are crushed into black. The flat grey field is the fairest uniformity test: move your head rather than the screen, because viewing angle on many panels changes brightness by itself. On a black screen in a dark room, glow in the corners that shifts as you move is normal on IPS panels; bright, stationary patches at the edges are backlight bleed, and that is what manufacturing tolerances are written about.
Things that look like faults but are not
Camera and video compression, dynamic contrast, energy-saving modes and 'game' picture presets all distort test patterns. A monitor's sharpness setting above neutral also creates halos on the cross-hatch grid. Before judging a panel, reset it to defaults and turn off picture enhancement, then re-test — then compare with a second source such as a laptop known to be good.
When to use this test
- A new monitor has arrived and you want to check it properly within the return window
- Dark scenes in games or films look patchy and you want to see whether it is the panel
- You are calibrating a display and need clean reference fields
- Judging whether to accept a refurbished screen with minor bleed