DisplayHDR 400, 600, 1000 and True Black: What the HDR Ratings Mean

HDR10 is a way of sending video: it carries a wider range of brightness and colour information than standard video. A monitor can advertise HDR10 simply because it can read that signal and map it onto its own, limited panel. This is sometimes called HDR input support rather than real HDR performance.

DisplayHDR is a VESA certification programme. Manufacturers submit a monitor to defined tests, and passing sets a tier. The number in the name corresponds to the minimum peak brightness in nits (candelas per square metre) that the display must sustain in the test patterns, such as 400, 600 or 1000.

Because the tiers are tested, they are more informative than a general HDR label. They are still a minimum bar, not a ranking of picture quality, and two monitors with the same tier can differ in panel type, contrast and colour. Use the tier as a filter, and use independent measurements for the details.

An LCD monitor uses a backlight that shines through the panel. Without local dimming, one backlight lights the whole screen, so bright highlights and dark areas share the same light and blacks look grey. Local dimming divides the backlight into zones that can dim independently. More zones generally mean better control, though the behaviour depends on the implementation, and some monitors show a halo around bright objects on dark backgrounds.

An OLED panel lights each pixel itself, so a black pixel is off. That explains why the True Black tiers have much lower peak brightness numbers than the LCD tiers while still looking contrasty in a dark room. In a bright room, the higher peak brightness of a high-tier LCD can look more impressive.

Peak brightness is also only available for part of the screen or part of the time. Many displays limit brightness when large areas are bright. Reviews that list brightness for a small window and for a full-screen white image, as well as black level and zone count, give a more honest picture.

When you read a review, look for several numbers rather than one. Peak brightness in a small window shows highlights, a larger window and full-screen white show how brightness drops with bigger bright areas, and black level shows contrast. Local dimming zone count and any blooming photos help with LCD models.

Colour volume matters as well. A wide gamut with good brightness gives richer colour in HDR, and gamut coverage figures are usually listed as a percentage of DCI-P3 or Rec. 2020. Treat these as the reviewer's measurements and note the test conditions.

Finally, remember the content. Not every game or video is mastered well for HDR, so a modest HDR tier can look fine in some titles and poor in others. Test with the content you actually watch if the retailer's return policy allows it.