SDR to HDR
Glossary

What is a nit in video?

A nit is one candela per square metre (cd/m²), the standard unit for how much light a display emits. SDR reference white is defined at 100 nits. HDR content is typically mastered on a display capable of 1,000 or 4,000 nits, and consumer HDR televisions peak somewhere between about 400 and 2,000.

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The numbers worth remembering

Reference pointBrightness
SDR reference white (BT.709)100 nits
Typical HDR mastering display1,000 or 4,000 nits
Consumer HDR TV peak, common range400 to 2,000 nits
PQ curve maximum10,000 nits

The PQ curve's 10,000-nit ceiling is headroom for the future, not a target. No consumer display comes close, and content mastered above 4,000 nits is rare.

Peak versus sustained

A display's advertised peak brightness is usually measured on a small window, often 10% of the screen area, held briefly. The same panel driven at full screen may deliver a fraction of that. This is why MaxFALL, the frame-average figure, exists alongside MaxCLL: a display needs to know both the brightest pixel and how much of the frame is bright, because sustaining a bright full-screen image is a thermal problem, not an optical one.

What "ten times the headroom" means

The common claim that HDR gives ten times the range comes from comparing SDR's 100-nit reference white to a 1,000-nit mastering target. It is a fair description of the encoding, not a promise about your display. What you actually see depends on the panel, and a 500-nit monitor showing a 1,000-nit master is tone-mapping every highlight above its ceiling.

Questions people ask

How many nits do I need for HDR to be worth it?

Roughly 400 sustained is where the difference starts being visible, and 600 to 1,000 is where it becomes obvious. Below about 350 a display accepts an HDR signal and then tone-maps it into a range that cannot show the headroom, which is why cheap HDR monitors disappoint.

Is a brighter display always better?

For highlights yes, up to a point, but peak brightness alone is misleading. A panel's advertised figure is usually measured on a small window held briefly; full-screen sustained output is often a fraction of it. Black level matters as much, which is why OLED at 800 nits can outperform LCD at 1,500.

Related: the numbers behind the headroom.

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