Overview
ISO/TR 17321-3:2017 provides guidance for user controls and readouts used in a scene-referred (SR) capture processing mode for digital still cameras (DSCs) and camera-raw processing software. The technical report defines how cameras and raw processors should present scene-referred information (colour encodings, readouts and mode indications) to help users produce colourimetrically accurate images of scenes and objects in controlled capture situations such as studio, reprographic and archival workflows.
Key topics and requirements
- SR capture intent: SR mode is intended for accurate scene colourimetry and is best used under controlled illumination; it is not targeted at general pictorial photography.
- Colour encodings & file format: Use scene-referred encodings (examples in the text: scRGB and RIMM RGB) and communicate the chosen encoding via file format metadata (e.g., embedded ICC profile).
- User readouts - L histogram*: Present a CIE L* histogram converted from scene-referred image values, displayed from “0” to “over 100” with main markers at L = 0, 50, 100* and sub-markers at 5 L* increments. Allow display of values above diffuse white (L* > 100) according to the encoding’s headroom.
- Clear SR mode indication: The UI should show when SR mode is active (labels such as “scene‑referred” or “SR”) so users know whether they are in SR or output-referred workflows.
- Raw processor guidelines: In SR mode the raw processor should convert raw files to scene-referred files with colour rendering disabled and use scene-referred encodings as defined in ISO 22028-1; it may accept recorded scene-adopted white (exposure/white balance) info.
- Capture controls - white balance & exposure: Provide controls for custom white balance using a full-frame reference target or a selectable preview region. Exposure guidance is based on reflective charts with known L* patches (e.g., set camera so the L* = 95 white patch maps to L* = 95).
Applications and users
This guidance is practically valuable for:
- Imaging specialists in archives, museums and cultural heritage digitization
- Artwork reproduction and reprographic photographers
- Camera manufacturers and firmware designers implementing SR capture modes
- Developers of camera-raw processing and image-management software
- Labs requiring traceable, colourimetrically accurate scene data for analysis or long-term preservation
Benefits include improved reproducibility of scene colours, clearer user feedback for exposure and white balance in SR workflows, and predictable interchange of scene-referred image files.
Related standards
Relevant documents cited by ISO/TR 17321-3:2017 include:
Keywords: ISO/TR 17321-3:2017, scene-referred, SR mode, digital still cameras, colour characterization, L* histogram, scRGB, RIMM RGB, raw processor, ICC profile, archival imaging.
Open preview (PDF)Graphic technology and photography — Colour characterization of digital still cameras (DSCs) — Part 3: User controls and readouts for scene-referred imaging applications
