MaxFALL, the Maximum Frame-Average Light Level, is a static HDR metadata value that states, in candelas per square meter (nits), the highest average brightness of any single frame in a program. In HDR video it travels together with MaxCLL, the brightest single pixel, and with the mastering display description, so that a television can judge how demanding the content will be before it starts tone mapping.
The value is defined in the CTA-861.3 specification and is part of the HDR10 static metadata set. It describes the content itself, not the monitor it was graded on, and a single number covers the entire film or episode.
How MaxFALL is calculated
MaxFALL is computed from the linear light values of the finished master, after the PQ transfer function has been decoded back to absolute luminance. The calculation follows a fixed sequence that analysis tools run over every frame.
- For each pixel, take the largest of its R, G and B components in nits; this is the pixel light level.
- Average the pixel light levels over the active picture to get the frame-average light level.
- Repeat for every frame of the program.
- The highest frame average found anywhere is the MaxFALL value.
Because MaxFALL uses the maximum RGB component rather than true luminance, a frame filled with saturated blue or red can score higher than its visual brightness suggests. The value is an integer in nits, and zero means unknown, which tells the display to make no assumption.
Measurement tools do not always agree on details such as whether letterbox bars count toward the average or how a brief flash frame is treated. Two analyzers can therefore report somewhat different MaxFALL values for the same master, so facilities usually standardize on one measurement tool for deliveries.
Typical values and what they mean
Most HDR programs have a MaxFALL far below their MaxCLL, because only small specular highlights reach peak brightness while large areas stay near SDR levels. The ranges below are typical orientation values, not limits from the specification.
| Content type | Typical MaxFALL | Reason |
|---|---|---|
| Dark drama or thriller | Below 100 nits | Low-key scenes with few bright areas |
| General feature film | About 100 to 300 nits | Mostly SDR-like levels with bright highlights |
| Bright nature or sports | About 300 to 600 nits | Large sunlit skies, snow or stadium lighting |
| Demo or showcase content | Can exceed 1,000 nits | Full-screen bright imagery by design |
A high MaxFALL is not a quality mark. It signals that the program contains full-frame bright scenes, which many displays cannot reproduce at full brightness for long.
Why displays care about frame-average brightness
HDR televisions, especially OLED panels, can reach a high peak only on a small window of the screen. When a large area turns bright, automatic brightness limiting reduces output to stay within power and heat limits. A display that knows the program MaxFALL can plan its tone mapping curve to anticipate that behavior instead of reacting abruptly.
In practice, display manufacturers decide independently how much weight to give the value. Some televisions use MaxCLL and MaxFALL as hints, others rely mainly on the mastering display peak or analyze the incoming picture themselves. The metadata is therefore advisory rather than binding.
MaxFALL compared with related HDR metadata
MaxFALL is one piece of a larger metadata picture. The table compares it with its neighbors in HDR delivery.
| Metadata | What it describes | Scope | Defined in |
|---|---|---|---|
| MaxFALL | Highest frame-average light level | Whole program, static | CTA-861.3 |
| MaxCLL | Brightest single pixel light level | Whole program, static | CTA-861.3 |
| Mastering display metadata | Primaries, white point, min and max luminance of the grading monitor | Whole program, static | SMPTE ST 2086 |
| Dynamic metadata | Brightness and tone mapping data per scene or frame | Scene by scene | HDR10+ and Dolby Vision |
The main limitation of MaxFALL is its static nature. One very bright scene sets the value for a two-hour film, even if every other scene is dim. Formats with dynamic metadata such as HDR10+ and Dolby Vision solve this by describing each scene separately, which lets the display preserve detail in dark passages.
Setting and checking MaxFALL in delivery
MaxFALL is measured on the final graded master, after all titles and effects are in place, and is written into the encoded stream. In HEVC it appears in the content light level information SEI message, and containers such as MP4 and MKV can store it at the file level as well.
| Problem | Cause | Remedy |
|---|---|---|
| Value set to zero | Metadata not measured or not passed through | Analyze the master and set the value explicitly |
| Value copied from another title | Template metadata reused | Measure every program individually |
| Value higher than expected | A white flash frame or bright title card | Review the frame and adjust the grade if unintended |
| Mismatch between files | Different tools or edits after measuring | Measure again after the last change |
Some streaming platforms and broadcasters publish recommended ceilings for frame-average brightness in their delivery specifications, because consistently bright programs tire viewers and stress displays. Colorists watch frame-average levels during grading so that the final MaxFALL stays comfortable for home viewing.
In simple terms
MaxFALL is a single number that describes how bright the brightest whole scene in a movie is. It does not look at one shining lamp or a reflection. It looks at the overall glow of the entire screen, and it reports the highest one.
A television reads this number before playback. It is a bit like a weather forecast for brightness. If the forecast says a very bright scene is coming, the television can prepare, so the picture stays smooth instead of suddenly dimming.
A practical example
A post-production team delivers a 50-minute HDR10 nature episode graded on a 1,000-nit mastering monitor. Most of the episode is forest footage, but one sequence shows a glacier in full sunlight. After the final conform, the analysis tool reports a MaxCLL of 980 nits and a MaxFALL of 540 nits, the latter set entirely by the glacier scene.
The delivery specification recommends keeping frame-average levels lower for comfortable viewing. The colorist reduces the overall level of the glacier sequence slightly, keeping highlights intact, and a new analysis gives a MaxFALL of 390 nits. The values are written into the HEVC stream, and on a home OLED television the glacier scene now plays without the visible dimming that the first version triggered.