SDR Trim Pass

Bridging the Gap Between Display Technologies

Today, most high-end films and television shows are color graded for High Dynamic Range (HDR). HDR displays, like premium 4K TVs or Dolby Cinema projectors, are capable of producing much brighter highlights, deeper blacks, and a wider range of colors than traditional screens. However, the vast majority of consumer devices—older TVs, laptops, tablets, and phones—are still Standard Dynamic Range (SDR).

Simply converting a vibrant HDR image directly to the more limited SDR color space often yields poor results. Highlights can become ‘clipped’ (blown out to pure white), shadows can be ‘crushed’ (losing all detail), and colors can appear muted or washed out. The creative intent of the original grade is lost.

The Two-Step Grading Process

To solve this, colorists use a two-step process:

1. The Primary HDR Grade: The colorist works with the director and cinematographer to create the definitive, ideal look of the film in a high-end HDR color suite. This is the ‘hero’ grade.
2. The SDR Trim Pass: After the HDR grade is locked, the colorist then performs the trim pass. They view the HDR master through a system that maps it down to the SDR color space. They then make a series of secondary adjustments—‘trims’—to the brightness, contrast, and saturation. These trims are designed to best approximate the look and feel of the HDR grade within the limitations of SDR.

These trim adjustments are saved as a layer of metadata alongside the primary HDR master. This creates a single, versatile master file. When the file is played on an HDR-capable device, it displays the full HDR grade. When it’s played on an SDR device, the device reads the trim metadata and applies those corrections on the fly, ensuring that the SDR version is a carefully considered and aesthetically pleasing representation of the filmmaker’s original vision.