MaxCLL Explained
Definition and Purpose
MaxCLL (Maximum Content Light Level) measures the single brightest pixel’s luminance within an HDR frame. It guides content mastering and display capabilities to ensure that specular highlights (e.g., sunlight glints, fire) remain within display tolerances.
MaxCLL: Technical Details
- Unit: Nits (cd/m²)
- Standards: HDR10 mandates reporting of MaxCLL in metadata; typical values range from 1,000 to 4,000 nits.
Role in HDR Workflow
During grading, artists use MaxCLL to evaluate specular peaks. Tools highlight clipping risks and allow graded maps to remap extreme highlights to display‑capable levels without flattening detail.
MaxCLL: Best Practices
- Limit MaxCLL to target display’s peak capability.
- Employ highlight roll‑off curves to soften abrupt transitions.
- Verify metadata accuracy in final deliverables.
MaxCLL: Trivia
- MaxCLL was introduced alongside HDR10 as part of SMPTE ST 2084 metadata requirements.
- Some displays advertise high MaxCLL handling but throttle sustained peaks to protect hardware.