Ghosting test

Ghosting, overshoot and blur

Match what you see around the shape to one of the four faults RTINGS names in its monitor motion tests.

• Ghosting A faint trail behind the shape: pixels still changing from the last frame's color.
• Overdrive overshoot A bright or dark halo the shape doesn't have: pixels pushed past their target shade. Reviews call it inverse ghosting.
• Motion blur A soft smear on both edges, even on a fast panel. Most of it comes from your eyes tracking the shape while each frame holds still.
• Dark smearing On a VA panel, a dark trail behind the black block on the mid and light bands, where pixels rise slowly out of black.

A shape that jumps instead of trailing has skipped a refresh, and the FPS test counts those as dropped frames.

Overdrive settings

Overdrive drives pixels harder to shorten the trail. DisplayNinja lists the names monitor menus use: Overdrive, OD, Response Time, or TraceFree on ASUS, with levels such as Normal, Fast and Faster. Too strong a level overshoots. RTINGS measured a 236% overshoot error on the ASUS XG27AQ at its strongest setting, on one transition to 20% gray.

The best level changes with the refresh rate, so tune it at the rate you play at, and confirm that rate with the refresh rate test. RTINGS also finds that a cold LCD responds more slowly, so let the screen warm up first.

GtG and MPRT

GtG (gray to gray) is how long a pixel takes to change shade; ghosting and overshoot happen during that change. MPRT (moving picture response time) is how long each frame stays on screen; RTINGS notes that on a normal sample-and-hold screen that is the whole refresh.

A web page can't see the pixels change, so here slow GtG shows up as trails and halos, with no time in ms. Response time also decides how much you gain from a faster refresh rate, whether you're weighing 60Hz vs 120Hz or 144Hz vs 240Hz.

Why a 1 ms monitor still blurs

Your eyes follow a moving object while the screen holds each frame still, so the image smears across your retina. RTINGS explains it with the Blur Busters Law: each millisecond of persistence adds 1 px of blur for every 1,000 px/s of motion. In RTINGS' motion photos, this hold causes most of the blur, not slow pixels. At 960 px/s that is 16 px of blur on a 60 Hz screen and 6.7 px at 144 Hz, even with pixels that change instantly. Move per refresh, in the test above, is that blur for your own screen and speed.

A 1 ms GtG rating can't shorten that hold. A higher refresh rate or a strobe mode can, and the frame rate comparisons list the blur at each common rate. In RTINGS' strobing tests, backlight strobing and black frame insertion cut persistence, at the cost of a dimmer picture and possible flicker. Brands sell it under names such as ULMB 2 (NVIDIA), ELMB (ASUS) and PureXP (ViewSonic).

How the ghosting test works

When you press Start, we time your screen's frames to measure its refresh rate. The shapes start moving on a first estimate after about a second. If your screen is faster than 60 Hz but the test finds 60, a setting, a cable or the browser is holding it back, and the refresh rate test names the likely cause.

• Counted refreshes. The shapes move a set distance per refresh, not per unit of time, so once the rate is locked a skipped refresh still moves them the full distance.
• Speeds. 960 px/s is the long-standing norm, and RTINGS now uses 1,920 px/s. They are in CSS pixels, the unit pages are laid out in.
• Flashing. Each pass of a shape flashes a point 3 or 4 times, so we keep the shapes small. The area that changes from one frame to the next stays under a quarter of the 341 by 256 CSS px block that the W3C's WCAG 2.3.1 (Level A) measures flashes in. Narrow screens also lose the fastest speed, as an extra margin.
• Backgrounds. Black, 50% gray and light gray, because RTINGS found that an overdrive level that helps dark scenes can overshoot in bright ones.
• Your eyes, not a camera. A camera on a tripod does not record persistence blur, so reviewers such as RTINGS use a pursuit camera that slides along with the pattern.

Nothing moves until you press Start, and it stops when you switch tabs.