The Contrast Number and the Room It Requires
A 1,000,000:1 contrast ratio measured in a dark lab with local dimming active tells you exactly one thing: what the panel can do when the test is designed to flatter it.
What the Spec Actually Measures
Full-on/full-off contrast ratio is sequential, not simultaneous. The panel displays a full-white field; luminance is measured. Then a full-black field; luminance is measured again. The ratio of those two readings becomes the headline number. At no point does bright content sit next to dark content on the same screen — which is precisely what every piece of real content requires.
The measurement happens in a darkened room, eliminating ambient light from the denominator entirely. On an LCD, local dimming is almost always active, so the backlight behind the black field dims to its minimum — a state that rarely applies to a mixed-luminance scene. On OLED, a full-black frame draws near-zero current from every pixel simultaneously, a condition that triggers power-management behaviour not present during normal viewing. The resulting black-level figure is the best the panel will ever produce, and it is being compared to the brightest white the panel will ever produce.
Put that panel in a living room with 200 lux of ambient illumination, display a dark scene with a bright highlight, and the effective contrast collapses. Ambient light reflects off the screen surface, raising the black floor. Local dimming halos bleed light into shadow areas. The ratio that reaches your eye is determined by screen reflectance, zone count, and the optical stack — none of which appear in the contrast ratio figure.
The number is real. The conditions that produced it are just nowhere near yours.