Black Smearing – Dark Blocks on Black at 3 Speeds

All 14 speeds, patterns and checks

Speeds 3

Drift over black, 480 pixels a second A slow slide, 8 pixels a frame at 60 Hz. A pixel change that takes 20 ms leaves a trail about 9.6 pixels long at this speed: small, but easy to see on dark grey.
Scroll over black, 960 pixels a second About the speed of scrolling a page, 16 pixels a frame at 60 Hz. A 20 ms change leaves a trail about 19 pixels long, the width of a word in small type.
Camera turn over black, 1,920 pixels a second A quick turn in a game, 32 pixels a frame at 60 Hz. Trails from slow dark changes are longest here, about 38 pixels for a 20 ms change, and hardest to ignore.

Show all 14 speeds, patterns and checks (11 more)

Dark patterns 5

Dark grey block on black, level 24 The core of the test: a very dark grey sliding over black. Every edge of the block asks pixels to change between two dark shades, and a slow change there shows as a shadow.
Deep grey block on black, level 48 A little lighter. If the trail behind this block is shorter than behind the level 24 block, the panel slows down as the shades it moves between get darker.
Black block on dark grey The same change the other way round: black moving over dark grey. A smear here trails behind the black block as a darker shadow, the classic look of black smearing in a dark game.
Four dark greys on black Four blocks from level 16 to 64 side by side. Compare their trails in one pass and note which levels drag a shadow and which move cleanly.
Mid grey block on black, for comparison A brighter block on the same black. If this one moves cleanly while the dark blocks trail, the smear comes from slow dark transitions, not from motion blur that affects everything.

What you see and what it means 3

A dark trail behind the dark blocks only The dark greys drag a shadow and the mid grey does not. That is black smearing: pixels changing too slowly between dark shades, so each dark edge lags behind the block.
The same soft edge on every block Every block, dark or mid grey, has a soft edge about one frame of travel wide. That is motion blur from the eye following a held frame, not smearing, and a higher refresh rate shortens it.
A bright halo instead of a trail A light fringe behind a dark block means overdrive is pushing the pixels past their target. Turn overdrive back down one step: the right setting leaves neither a shadow nor a halo.

What to change 3

Raise overdrive one step Overdrive, often listed as response time in a monitor menu, drives pixels harder so they change sooner. Raise it one step, run the dark block again, and stop at the first setting that brings a halo.
Test at the refresh rate you use Trails and halos can change with the refresh rate, and overdrive is often tuned for the top rate. Run the test at the rate your games actually reach, then at the monitor's maximum.
Photograph the trail with a fast shutter Your eye blurs a moving block. A phone camera following the block, or a photo at a short shutter speed, shows the trail itself. Keep the photo as a record of each overdrive step.

How this list was compiled: Speeds, patterns and checks written for this page; the moving shapes are this site's own plain blocks. Every figure was computed: pixels a frame are speed divided by refresh rate, and trail length is speed times the time a pixel change takes (20 ms at 960 pixels a second is 19.2 pixels). Eye-tracking blur on a screen that holds each frame, and its shortening at higher refresh rates: https://en.wikipedia.org/wiki/Display_motion_blur. How overdrive works (a higher first voltage so a pixel changes sooner): https://en.wikipedia.org/wiki/Response_time_compensation. That VA grey-to-grey changes run at about 14 to 30 ms without overdrive and that some stay above 10 ms with it, while others reach about 4 ms, and overshoot (a halo) from overdrive set too strong: https://pcmonitors.info/articles/factors-affecting-pc-monitor-responsiveness. All read 2026-09-24. The page names no panel type as the cause and measures nothing: the trail is judged by eye. Licence: own work

How it works

Black smearing is a dark shadow that trails dark objects moving over black. This test slides very dark greys across black at three speeds, beside a mid-grey block for comparison. Press Start, then pick what you see.

Read the full guide

Smear or blur

If the dark blocks drag a shadow and the mid-grey block moves cleanly, the panel is slow between dark shades: black smearing. If every block has the same soft edge, one frame wide, that is motion blur, which a higher refresh rate shortens.

A black smearing monitor setting to try

Raise overdrive one step and run Dark grey block on black, level 24 again. Stop at the first step that leaves a bright halo, then go back one. Test at the refresh rate your games reach.

Follow the block with your eyes, or film it with a phone moving at the same speed: a still camera only shows blur.

Questions and answers

What is black smear on a monitor?

A black smear monitor fault is a dark trail behind dark objects on a dark background, as when a character walks through a night scene. It comes from pixels changing slowly between dark shades, and it is judged by eye.

Can black smearing be fixed?

It can often be reduced, not removed. A stronger overdrive setting speeds up pixel changes, at the risk of a bright halo. Test each step here and keep the last one before the halo appears.

Does this page measure response time?

No. It shows moving shapes and names what you might see, but it times nothing. For the full set of greys and overdrive halos on light backgrounds, use the monitor ghosting test.

Black Smearing Test for Monitors