HDR10 vs HDR400: a signal format and a brightness tier
By TechCompare · Updated · How we check
HDR10 is a format: the screen can decode the signal. DisplayHDR 400 is a certification: the screen reached 400 nits, kept black at 0.4 nits or less and met VESA's color and speed rules. Only the second says anything about picture quality.
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HDR10
- What the logo tells you
- Nothing about quality. It's the base signal nearly every HDR screen accepts, so a cheap monitor and a top TV both list it.
- Metadata
- Static: one set for the whole video (SMPTE ST 2086 mastering data, plus MaxCLL and MaxFALL).
- Signal curve
- PQ (SMPTE ST 2084). Each code value stands for a set brightness in nits.
- Bit depth
- 10 bits
- Color primaries
- BT.2020
- Without support
- Not backward compatible with SDR. An SDR screen needs the player to convert it.
- License
- Free to use.
- Who made it
- Announced by the Consumer Technology Association (then the CEA) in August 2015.
- What the screen still needs
- Enough brightness and contrast to show the range the video was mastered for. The screen tone maps whatever it can't reach.
Source: Wikipedia, HDR10
HDR10 and HDR400 look like rival standards on a spec sheet, but they answer different questions. HDR10 says which HDR signal a screen accepts. DisplayHDR 400, often shortened to HDR400, says how bright, dark and colorful the screen got in VESA's tests. A monitor can list HDR10 without any DisplayHDR tier.
How this is calculated
HDR10 is the base HDR format. The Consumer Technology Association, then the CEA, announced it in August 2015. It uses the PQ curve, 10-bit color and BT.2020 primaries, with one set of static metadata for the whole video. It's free to use, so nearly every HDR screen accepts it.
Accepting a signal isn't the same as showing it well. A monitor only has to decode HDR10 and tone map it to what the panel can do. One that barely gets brighter than an SDR monitor can still list HDR10, and the picture will look like SDR with different colors.
DisplayHDR 400 sets a floor. Under CTS 1.2 it asks for 400 nits on a small patch, 320 nits on a full screen held for a long time, a black level of 0.4 nits or less, 90% of DCI-P3 and a 10-bit signal. It's a modest floor, but it's measured. If a box says HDR400 and the model isn't on VESA's certified products list, it hasn't passed those tests.
Read the two together. HDR10 tells you HDR content will play. A DisplayHDR tier, or a review with measured numbers, tells you how it will look.
Verdict
Treat HDR10 on a spec sheet as a given and look past it. The DisplayHDR tier, or a review's peak brightness and black level, decides what HDR looks like. A monitor with HDR10 and no tier can still be fine for SDR, but don't expect much from its HDR.
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Frequently asked questions
Is HDR10 better than HDR400?
What does HDR400 mean on a monitor box?
Can a monitor support HDR10 without being bright?
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