Monitor test

Black screen and white screen

Clean the screen first, as Dell advises: dust wipes off, a pixel fault stays. On black, look for lit dots and, on an LCD, light at the edges: backlight bleed or IPS glow. On white, look for dim areas and for dark dots, the sign of a dead pixel.

Black level and contrast

The black level pattern shows squares at levels 1 to 20 of 255 on black. White saturation shows 235 to 254 on white. RTINGS's settings guide says you should see every square, the faintest ones only just. Missing dark squares mean crushed shadows, and missing light squares mean clipped whites. A gray background means black level is set too high. The contrast bars should step evenly.

Turn off local dimming first: RTINGS finds it can crush dark detail. Turn off HDR too, since Microsoft says it can wash out SDR in Windows.

Gamma and gradients

Set 100% zoom and your native screen resolution, then step back from the gamma chart until its one-pixel stripes blur. The patch that matches them is your gamma. RTINGS says most monitors default to 2.2. Stripes, jumps or tints in the gradients are color banding.

Sharpness and uniformity

If the text and line blocks have halos, sharpness is set too high; if they blur, it's too low, RTINGS explains. Colored fringes around text come from the subpixel layout of QD-OLED and WOLED panels, and they fade as pixel density rises.

On the gray field and the grid, look for dark corners and clouds: RTINGS counts both as poor gray uniformity. A faint logo left on an OLED's gray is image retention or burn-in. If a TV cuts off the grid's border, it is cropping the picture; LG's Just Scan setting stops that for HD signals (720p, 1080i, 1080p).

Signs of a bad monitor

Dell's guidelines count a dot that stays in one spot as a pixel fault. Lines across the screen and patches bigger than a pixel are a different fault. Two more signs only show in motion: ghosting trails behind moving objects, and a fast monitor whose refresh rate is stuck at 60 Hz.

Phone and laptop screens

Before you start, turn off True Tone, Night Shift and Auto-Brightness on an iPhone, Night Light and adaptive brightness on a Pixel, or Night light and content-based brightness on Windows. Each one changes the picture on its own.

How the monitor test works

Every pattern is made at your screen's own pixel count, at 8 bits per channel (256 levels), in sRGB. Those are the web's defaults: MDN gives 8 bits as a canvas's default depth, and the W3C's CSS Color 4 makes sRGB the default color space. A color profile on your computer can adjust the patterns after they leave the page, and we can't see that.

Nothing is measured here; you judge by eye. The patterns are based on Han-Kwang Nienhuys's Lagom LCD monitor test pages (2008), redrawn from scratch.