The surround — the dimly lit area behind and around your display — should meet SMPTE and ITU standards for accurate viewing. This tool maps how your bias light will illuminate that zone based on your installation geometry: strip placement, setback distance, LED density, and display orientation.
Each segment of the LED strip acts as a point light source. Intensity at any wall point follows the inverse square law: I = cos(θ) / d² where d is the distance and θ is the angle from the beam axis. The heatmap shows this directly — areas further from the strip are genuinely dimmer.
The setback (distance from back of display to wall) is the primary driver of how widely light spreads. A larger setback lets light diverge before hitting the wall, producing a wider, softer halo. A display mounted flush produces a narrow, intense band close to the strip positions.
Gallery mounts — flush or near-flush wall mounts — are increasingly common, and they present a real tradeoff. With only a fraction of an inch between the back of the display and the wall, there is very little room for light to escape sideways, so the visible surround will be narrower and dimmer than a standard installation. This is physically unavoidable. The workaround is to run the strip at a higher drive level so that the light reaching the visible surround is still bright enough to meet the ~10% reference surround luminance target. That's achievable in practice — reference bias lighting doesn't need to be particularly bright — but you should go in with realistic expectations about spread.
The temptation in a gallery mount is to move the strip to the very edge of the display to maximize the light that escapes. Resist this. The 2″ inset recommendation exists for exactly the reasons described below — hotspot reflections, uniformity, and chromaticity integration all get worse as the strip approaches the edge. Moving the strip outward to compensate for low setback trades one problem for several others. The better answer is simply more drive current, not a different strip position.
Display tilt shifts the intensity peak. Tilted slightly down (common for high wall mounts) redirects the beam upward on the wall, brightening the area above center.
Why 2″ inset? Three distinct problems arise from placing the strip too close to the edge.
Hotspot reflections: at typical viewing distances, individual LED points become visible as discrete reflections in the wall surface — particularly on semi-gloss or lightly textured walls.
Brightness uniformity: LEDs have a 120° beam angle and need throw distance for adjacent beams to overlap and fill in. With too little setback and a tight inset, each LED lands as a distinct bright spot rather than a smooth continuous surround. The integration cross-section below shows this directly — 20 LEDs/m requires more throw to fill the gaps than 30 or 60 LEDs/m.
The hidden zone: the area of wall directly behind the display — where beam overlap is lowest and individual LEDs are closest — is not visible from a normal seating position. The light reaching the visible surround around the display has already traveled further, allowing adjacent beams to blend. In practice, brightness uniformity is a concern for the zone behind the screen, not the lit area you actually see. Depending on your seating position, viewing angle, and display thickness, you may or may not have a sightline to this area.
Shadows: anything within the light strip perimeter — the display chassis, VESA mount, cables — will cast shadows on the wall behind the display, which is hidden from view. Objects outside the strip perimeter, such as VESA arms or cables routed along the outside of the strip, may cast shadows on the visible wall. This does not affect the performance of the bias light, but some people find it visually distracting. Keeping all hardware and cables within the strip perimeter is good practice.
Chromaticity uniformity: this one is subtle but measurable, and it applies to every undiffused phosphor-converted white LED — which covers virtually all white LEDs, from commodity to high-CRI. The blue InGaN emitter sits at the center of the die; the phosphor conversion (yellow-green in standard chips, a richer multi-phosphor blend in high-CRI chips) surrounds it as a halo. Without sufficient throw distance these two zones don't fully mix, and different parts of the wall receive light with slightly different chromaticity coordinates. The variation is invisible to the eye but will show up on a spectrophotometer. High-CRI chips still exhibit this because, despite their richer phosphor blend, they rely on a pronounced blue emitter peak. Chips engineered with a less dominant blue peak have a smaller inherent emitter-to-phosphor delta to begin with, making integration somewhat more forgiving — but the principle applies universally to all undiffused phosphor-converted sources.