Nits (brightness) – HDfury Vertex glossary
Nits measure how bright a screen is. HDR uses nits to describe bright highlights and what a display can show.
A nit is a unit for how much light a screen gives off. More nits means a brighter picture.
Think of it like a ruler, but for light instead of length. An HDR movie uses nits to say how bright each part of the picture should be, and the screen tries to follow.
Can the HDfury Vertex change HDR brightness (nits)?
PARTLYPartly. The Vertex does not make the picture brighter. It shows the brightness values the source sends and can replace them with your own (max/min luminance, MaxCLL, MaxFALL); how the display reacts depends on the display.
How to use it with the Vertex:
- Read the incoming Max/Min Luminance, MaxCLL and MaxFALL (in cd/m²) on the OLED HDR pages (p.19).
- In the USB GUI, open the HDR INFOFRAME tab and enter your own values in the Custom HDR metadata generator (p.32–33).
- Tick Enable Custom HDR to send them; this setting stays on after hotplugs and power cycles (p.32).
- Turn it off again in the GUI, with RS232 #set hdrcustom off (p.51) or the IR code vertex_hdrcustomoff (p.77).
What it is
One nit is one candela per square metre (cd/m²), the standard unit for the brightness (luminance) of a screen. Normal SDR video is usually made for a screen of about 100 nits. HDR video can ask for much brighter highlights: the PQ curve used by HDR10 and Dolby Vision can describe up to 10,000 nits, and films are often mastered on monitors of 1,000 or 4,000 nits.
No home screen shows 10,000 nits. When a film asks for more nits than your TV or projector can make, the display has to squeeze the bright parts into its own range. That is called tone mapping. This is why the same HDR film can look different on a bright TV and on a projector, which usually makes far fewer nits than a TV.
HDR signals often carry a few brightness numbers as metadata: the peak and minimum brightness of the mastering monitor, MaxCLL (the brightest single pixel in the film) and MaxFALL (the brightest average frame). The display may use these numbers to plan its tone mapping.
On the Vertex
The Vertex does not make your screen brighter or darker. It only reads, passes or rewrites the brightness numbers that travel with the signal. The OLED HDR pages show the incoming values, such as Max/Min Luminance, MaxCLL and MaxFALL in cd/m², so you can see what the source sends (p.19).
In the USB GUI, the HDR INFOFRAME tab has a CUSTOM HDR METADATA GENERATOR. There you set Max Luminance, Min Luminance, MaxCLL and MaxFALL yourself and send them with the signal (p.32–33). The factory values in that generator are 4000 max, 0.005 min, MaxCLL 1000 and MaxFALL 400 (manual screenshot, p.32). Changing these numbers only changes what the display is told; how it reacts depends on the display.
Common questions
How many nits do I need for HDR?
There is no single number. More nits lets a screen show bright highlights closer to how they were mastered, but good tone mapping matters just as much, especially on projectors.
Is a nit the same as a lumen?
No. Lumens measure the total light a projector puts out; nits measure how bright a surface looks. The nits you get from a projector depend on the lumens, the screen size and the screen material.
Can the Vertex make HDR brighter?
Not directly. It can change the HDR brightness numbers sent to the display (p.32–33); some displays then choose a different tone-mapping curve, others ignore them.