Halo and black lift
Look for light around a highlight or a larger nearby region becoming greyer. Zone size, LCD contrast, diffuser behavior, algorithm choices, room light, and viewing angle can all influence the observation.
Observe the algorithm, not an invented zone map
Local Dimming Test
The local dimming test creates scenes that ask a zone-controlled LCD backlight to respond to several bright and dark regions at once. Adjust target count, source level, size, speed, and star density while watching for halos, delayed transitions, nearby black-level lift, visible pumping, or flicker. The page cannot enable local dimming, read its state, or count physical zones.
Compare scenes in a fixed order
Run the local dimming test in four stages
- Establish one picture-mode baseline. Use the display at your ordinary viewing position with a known local-dimming menu setting. Note SDR or HDR mode separately; the browser pattern and device processing may differ between those signal paths.
- Start with four moving targets. Watch the black just ahead of and behind each object. A delayed brightening or darkening may indicate transition behavior. Pause motion to separate a static halo from a time-dependent response.
- Increase target count and star density. Distributed highlights can require more simultaneous backlight decisions. Note whether blacks lift across a broad area, highlights dim, or the picture changes as density increases; do not infer one target per zone.
- Compare checkerboard, sweep, and static stress. The checkerboard tests adjacent bright/dark demands, the inward sweep exposes transition timing, and the static layout lets you study several sizes without motion. Repeat after changing only one device-menu option.
Describe behavior instead of scoring it
What to watch during a local dimming test
Transition delay
A brightened region may appear to lead or trail a moving object. Compare at slow speed, then pause. Browser animation timing also contributes, so this is not a measured backlight response time in milliseconds.
Pumping or flicker
Scene brightness may shift visibly when highlights enter or leave. If it occurs, note the pattern, density, and display setting. The page cannot determine whether firmware, signal conversion, or another processing stage is responsible.
Bright/dark tradeoff
Some algorithms reduce small highlight intensity to preserve a dark background; others allow more halo to keep the highlight bright. A visual comparison shows the chosen behavior but cannot report physical contrast or luminance.
A different purpose from blooming
Several dynamic demands reveal algorithm behavior
The blooming test isolates one square, circle, sparse point set, or subtitle surrogate so the halo around a simple highlight is easy to inspect. This local dimming test instead varies simultaneous targets and movement across the field. It is better suited to observing how a dynamic zone algorithm balances competing regions.
OLED does not use a zone-based LCD backlight, so this workflow should not be described as an OLED local-dimming diagnosis. Self-emissive displays can still change highlight output, apply tone mapping, or show temporal behavior, but the physical mechanism and appropriate interpretation are different.