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