Tone Mapping

Tone mapping is the algorithmic compression of a high-dynamic-range image into a smaller dynamic range for display, preserving as much perceived detail as possible despite the substantial luminance reduction. In modern post-production, tone mapping is essential when downconverting HDR masters to SDR deliverables (the 'HDR-to-SDR trim'), but it also occurs implicitly whenever camera log footage is converted to a viewing display look (log-to-Rec.709 LUTs are tone-mapping operations), and when HDR content plays on a display incapable of the master's full peak luminance (the display's internal tone mapper, or a streaming platform's bitstream metadata-driven adaptation, handles the reduction). Tone mappers differ in approach: global tone mappers apply a single curve across the whole frame (computationally cheap, may compress local contrast); local tone mappers analyze regions and compress differently in shadows, midtones and highlights (better visual preservation but slower); content-aware tone mappers use metadata or AI to adapt scene-by-scene. The Hable filmic tone curve, Reinhard tone mapping, ACES RRT, and Dolby Vision's content-aware mapping are well-known examples. In HDR-to-SDR trim, colorists may override automatic tone mapping with manual shot-by-shot work to preserve creative intent — particularly in highlights where automatic mapping can flatten dramatic specular detail. Reference: SMPTE published technical reports on HDR-to-SDR tone mapping, and Dolby Vision documentation covers their proprietary approach.