Luminance range
How to translate luminance technically between source and target: clipping, shoulders, global/local mapping, PQ EETF, HDR-to-SDR, display mapping and ordering in Resolve.
Tone mapping is controlled remapping of brightness relationships when the target cannot directly reproduce the source range. Good mapping preserves hierarchy and detail; Contrast merely reshapes an image within its current state.
Quick reference
Everything above the ceiling collapses to one value.
Especially important for PQ master → lower-peak display.
TONE MAPPING
Tone mapping is needed when a source/rendered image contains luminance relationships the target display/output cannot reproduce directly, such as a 4000-nit PQ master on a 700-nit television or an HDR master into 100-nit SDR. If source and target already match, an extra tone mapper can only damage an already-correct rendering.
Everything above the target ceiling collapses to one value. The output technically fits the range, but highlight texture and separation disappear. Clipping can be useful as a diagnostic or deliberate look, but it is not a general HDR mapping method.
Instead of an abrupt cutoff, mapping gradually compresses the upper range toward target peak. Important decisions include where compression begins, how smoothly it increases and whether the middle/diffuse region remains stable. A good shoulder preserves a sense of brightness without turning every highlight into a grey mass.
A global algorithm applies one luminance mapping relationship to a frame/scene. Local or adaptive algorithms analyse spatial context and can preserve more local contrast under heavy compression. The cost can be halos, temporal pumping and changes to creative intent, so a mastering pipeline generally needs more predictability than consumer-display enhancement.
In HDR-to-lower-HDR mapping, it is often desirable to preserve diffuse/reference white and midtones while concentrating compression in the upper highlight region. Faces and ordinary surfaces then retain continuity between displays while mainly the available highlight sparkle changes.
A PQ master carries absolute-luminance intent, but a lower-peak display cannot reproduce the source EOTF one-for-one. BT.2390 describes the EETF concept for controlled rendering to a limited display: PQ is interpreted correctly first, then the luminance range is adapted to the target.
An SDR output normally has a different reference white/peak, may have a smaller gamut and uses different viewing assumptions. HDR-to-SDR output transforms therefore solve tone mapping together with gamut mapping and display rendering. Compressing highlights first and independently crushing saturation later can damage hue and skin.
Creative Contrast/Curves shape the look inside the chosen working state. Technical tone mapping makes that look fit the target dynamic range. If both jobs are mixed in one node, changing the output from 1000-nit HDR to SDR forces the creative grade to be rebuilt. Scene-referred workflows are valuable precisely because they separate these layers.
Scene-linear/scene-referred exposure and highlight recovery generally belong before destructive display tone mapping. Display-referred tweaks after mapping operate on the rendered image. The same Gain or Soft Clip cannot be moved across the output transform with an expectation of identical behaviour.
In RCM/ACES, part of tone rendering already lives in the Output/Display Transform. In a manual CST pipeline, tone mapping can be handled by the output CST/DRT. Do not add a second CST, LUT or HDR-to-SDR mapper 'just in case'; stacking multiple shoulders often produces muddy highlights and weak contrast.
Do not judge mapping only by the absence of clipping. Compare diffuse white, skin, key highlights, specular texture, black level and overall contrast on the target display. Scopes should reveal where compression begins and what happens to peaks; visually, check whether the relative hierarchy between objects is preserved.
If tone mapping is obvious as a separate effect, it is often too aggressive. Its job is to make the target display look plausible while preserving intent, not to advertise the algorithm.
Technical definitions are anchored to standards bodies and primary specifications wherever that distinction matters.
EETF and display mapping for PQ/HLG HDR.
Standardised report on HDR↔SDR conversion methods.
Reference levels and practical conversion context.
RCM/CST tone mapping, HDR palettes and output workflows.
