ISO 22028-3:2023

Overview

ISO 22028-3:2023 - "Photography and graphic technology - Extended colour encodings for digital image storage, manipulation and interchange - Part 3: Reference input medium metric RGB (RIMM RGB)" defines a family of scene-referred, extended-gamut RGB colour image encodings for professional still-image workflows. The standard specifies RIMM RGB and its variants - ERIMM RGB (extended luminance dynamic range) and FP‑RIMM RGB (floating-point expression) - to enable reliable storage, manipulation, interchange, display and printing of scene-referred images without committing to a final rendering intent.

Key topics and technical requirements

• Scene-referred extended gamut encoding: RIMM RGB is designed to represent scene colours beyond typical display/output gamuts, preserving colours captured by cameras or film.
• Precision and formats:
  • RIMM RGB: 8-, 12- and 16-bits per channel.
  • ERIMM RGB (HDR-aware): 12- and 16-bits per channel.
  • FP‑RIMM RGB (floating point): 16-, 32- and 64-bit floating-point channels (IEEE 754 referenced).
• Colourimetry foundations: Encodings are defined relative to adopted white, reference medium primaries and a white point, with normative reference to ISO/CIE 11664-1 (CIE standard observers).
• Transforms and functions:
  • Conversion matrices between RIMM RGB and CIE tristimulus values.
  • Colour component transfer functions and digital encoding functions for RIMM RGB and ERIMM RGB.
  • Complete inverse transformations to recover tristimulus values from encoded data.
• Interoperability and documentation: The standard includes informative annexes (e.g., example transform to ROMM RGB and cultural heritage guidance) and normative references ensuring predictable colour handling across systems.

Practical applications and users

ISO 22028-3:2023 is aimed at workflows that need to retain full scene information and colorimetric precision prior to rendering:

• Professional photographers and retouchers - maintain full colour and luminance information for flexible later rendering.
• Imaging software and pipeline developers - implement standardized encodings, transfer functions and matrix transforms for consistent processing.
• Camera and scanner manufacturers - produce scene-referred raw pipeline outputs compatible with interchange formats.
• Cultural heritage digitization and archives - preserve accurate scene data for conservation, analysis and long-term storage (see Annex B).
• Print and color management specialists - convert reliably from scene-referred RIMM to output-referred encodings (e.g., ROMM RGB) for rendering.

Related standards

• ISO 22028-2: ROMM RGB (output‑referred wide RGB encoding) - complementary for rendering/output workflows.
• ISO/CIE 11664-1 (CIE standard colorimetric observers) and IEEE 754 (floating-point arithmetic) - normative references used by ISO 22028-3.

Keywords: ISO 22028-3:2023, RIMM RGB, ERIMM RGB, FP‑RIMM RGB, scene-referred, extended colour gamut, HDR, colour encoding, photography, graphic technology.