DisplayHDR 400 does not require local dimming. It also permits a black level as high as 0.4 nits. Those two lines alone fix the minimum contrast the certificate guarantees at 400 ÷ 0.4 = 1,000:1 — the same ballpark as an ordinary IPS panel that makes no HDR claim at all. Divide the figures in VESA's published DisplayHDR performance criteria and it becomes clear what the 400, 600 and 1000 in the tier names actually buy.
The tier name refers to peak luminance and nothing else. What makes a screen look like HDR lives in black level, local dimming architecture and the brightness sustained across a full white screen — and those three jump discontinuously between tiers.
400 is peak luminance, not full-screen brightness
VESA measures brightness three ways: peak luminance on a centre patch covering 8% of the screen, a short full-screen flash, and long-duration luminance holding full-screen white for 30 minutes. Only the first appears in the tier name.
Long-duration requirements are 320 nits for DisplayHDR 400 and 500, 350 for 600, 600 for 1000 and 900 for 1400. As a share of peak, that is 80% for the 400 tier, 58% for 600 and 60% for 1000. The 400 tier scores highest on that ratio only because its peak bar is low to begin with, not because it holds brightness better. HDR impact comes from how hard a display can punch a momentary highlight, and at 400 the available swing is simply narrow.
The contrast floor implied by the certification
Divide peak luminance by the allowed black level and you get the contrast ratio that tier guarantees. Real products may do better, but this is the floor the certificate promises. The table below applies the CTS 1.2 figures directly.
| Tier | Peak (cd/m²) | Black level cap (cd/m²) | Guaranteed contrast | Long-duration ÷ peak |
|---|---|---|---|---|
| DisplayHDR 400 | 400 | 0.4 | 1,000:1 | 80% |
| DisplayHDR 500 | 500 | 0.1 | 5,000:1 | 64% |
| DisplayHDR 600 | 600 | 0.1 | 6,000:1 | 58% |
| DisplayHDR 1000 | 1000 | 0.05 | 20,000:1 | 60% |
| DisplayHDR 1400 | 1400 | 0.02 | 70,000:1 | 64% |
| True Black 400 | 400 | 0.0005 | 800,000:1 | 63% |
| True Black 500 | 500 | 0.0005 | 1,000,000:1 | 60% |
| True Black 600 | 600 | 0.0005 | 1,200,000:1 | 58% |
Stepping from 400 to 500 raises peak luminance by 25% but multiplies guaranteed contrast fivefold, because the black cap drops from 0.4 to 0.1 nits. Going from 500 to 600 improves contrast by only 20%, since the black requirement is unchanged. The real jumps cluster at 400→500 and 1000→1400; 500→600 delivers less than its name suggests.
The tier name talks about brightness, but black level is what separates the tiers.
What none, 1D and 2D dimming actually change
Local dimming is the mechanism behind those black levels. VESA requires none at the 400 tier, 1D (edge-lit zone segmentation) at 500 and 600, and 2D (full-array) at 1000 and 1400. Without local dimming the backlight brightens or dims as a single block, so dark areas rising along with bright ones is structurally unavoidable.
The difference between 1D and 2D is the direction the zones are cut. Edge-lit arrays control LEDs along the border in columns or rows, so an entire strip lights up around a bright object. A full array is divided into a grid and can raise only the region around the highlight. The smaller the area one zone covers, the less light bleeds — the same arithmetic laid out in the piece calculating dimming-zone area for mini-LED versus OLED.
| Requirement | HDR 400 | HDR 600 | HDR 1000 | True Black 400 |
|---|---|---|---|---|
| Local dimming | Not required | 1D | 2D | N/A (emissive) |
| DCI-P3 coverage | 90% | 95% | 95% | 90% |
| Full-screen flash (cd/m²) | 400 | 600 | 1000 | 250 |
| Rise time (frames) | 8 | 2 | 2 | 8 |
Rise time deserves a second look. Only the 400 tier and True Black 400 are allowed 8 frames; everything else must hit 2. Slow luminance transitions can therefore pass certification, meaning panels that lag on fast-moving content can sit inside the 400 tier.
Why True Black exists as a separate family
True Black is the family VESA created for OLED and other emissive displays. Because pixels emit and switch off individually, the black-level bar drops to 0.0005 nits — between 40 and 800 times lower than the standard family. That is why True Black 400 lands at 800,000:1 in the table above.
The trade is full-screen output. True Black 400, 500 and 600 require full-screen flash luminance of 250, 300 and 350 nits respectively, below the 400, 500 and 600 nits demanded of the identically numbered standard tiers. The difficulty emissive panels have driving an entire screen evenly is written straight into the spec. For a bright living room in daylight, that line matters more than the contrast figure.
Tiers differ in character within the family too. In announcing True Black 500, VESA described it as matching the 600 and 1000 tiers on colour gamut, black level and bit depth with only a small luminance reduction — optimised for very slim, small displays but applicable to all sizes including monitors. Products split the same way: among the displays ASUS announced at Computex 2026, the ROG gaming OLED carries True Black 600 while the ProArt line carries True Black 500.
Who each tier suits, and who should wait
Here is what the published certification criteria alone support.
- If a DisplayHDR 400 badge is your reason to expect HDR, wait. With no dimming requirement and a 1,000:1 floor, the depth you want in dark scenes is not underwritten by the certificate. As a brighter office panel, 400 still means something.
- For film and gaming in a dark room, True Black fits. The 0.0005-nit black bar lifts contrast into the hundreds of thousands to one. The catch is the 250–350 nit full-screen requirement, which costs you in a bright room.
- For a bright living room or a desk by a window, look at 1000 and up. The 600-nit long-duration bar starts at that tier.
- If 600 costs meaningfully more than 500, the case for it is thin. The identical black requirement leaves only a 20% contrast gap. DCI-P3 coverage does rise from 90% to 95%, so colour work is the argument that holds.
- An unbadged ‘HDR supported’ claim is not a specification. DisplayHDR is awarded only after passing the CTS 1.2 test procedure; without it, none of the floors above apply.
For the signal-format side of the question, the companion piece is the comparison of Dolby Vision and HDR10. Panel certification and content format are two different layers.
