MaxCLL & MaxFALL – HDfury Vertex glossary
Two HDR10 light-level values: the brightest pixel and the brightest average frame in the content.
MaxCLL and MaxFALL are two numbers sent with HDR10 video that tell the screen how bright the film gets.
MaxCLL is the brightest single dot in the whole film; MaxFALL is the brightest average of one whole picture.
The screen can use them to plan how to fit very bright scenes into what it can show.
Can the HDfury Vertex show and change MaxCLL and MaxFALL?
YESYes. It decodes the incoming HDR metadata, including MaxCLL and MaxFALL, on the GUI, OSD and OLED HDR pages, and the custom HDR generator lets you set both (1–65535) and send them instead (p.32–33, p.42).
How to use it with the Vertex:
- Read the values on OLED page 3 or 4 (HDR 1 / HDR 2) (p.42).
- Or look at CAPTURED HDR METADATA in the HDR INFOFRAME tab (p.32).
- Set MaxCLL and MaxFALL in the generator, then Create IF and Send HDR (p.33).
- Untick Enable Custom HDR to stop sending your values (p.33).
What it is
MaxCLL (Maximum Content Light Level) is the light level of the brightest pixel anywhere in the content. MaxFALL (Maximum Frame-Average Light Level) is the highest average light level of any single frame. Both are given in cd/m² (nits).
They are part of HDR10 static metadata, next to the mastering display's maximum and minimum luminance. A display can use them to decide how much tone-mapping a title needs. Many titles send 0 or leave them out, which means 'unknown'.
On the Vertex
The Vertex decodes captured HDR metadata into readable text on the GUI and the OSD (p.32), and the OLED has two HDR pages (p.42).
In the Custom HDR metadata generator you can set MaxCLL and MaxFALL yourself, together with Max Luminance and Min Luminance. Each field accepts 1 to 65535 (p.33). Create IF builds the metadata and Send HDR injects it (p.33).
Common questions
What does it mean when MaxCLL and MaxFALL are 0?
0 means 'unknown'. Many discs and streams leave them out, and the display then uses other information, such as the mastering display's maximum brightness.
Can I change MaxCLL and MaxFALL with the Vertex?
Yes, in the Custom HDR metadata generator on the HDR INFOFRAME page. Each field accepts 1 to 65535; Create IF builds the metadata and Send HDR injects it (p.33).
Where can I see the values of what I am watching?
The Vertex decodes captured HDR metadata on the GUI and the OSD (p.32), and the OLED has two HDR pages (p.42).