What is Radiance HDR?
Radiance HDR is a high-dynamic-range image format developed for the Radiance rendering system and commonly identified by the HDR extension. RGBE represents each pixel with three color bytes and one shared-exponent byte.
How Radiance HDR works
Radiance HDR stores each pixel with three mantissa-like color bytes that share one exponent, providing a compact way to span luminance far beyond display-referred integer images. The file header carries descriptive variables and a resolution-orientation line, and scanlines may use run-length coding to reduce repetition. It is commonly read as scene-referred lighting data for renderers and environment maps, then tone-mapped or converted when preparing a conventional display asset.
A parser reads the file structure, identifies contained streams and metadata, and exposes them to a decoder or application. Conversion usually decodes the source representation and writes compatible information into a different structure or encoding.
A format may describe a container, a bitstream, or both, and the filename extension can be misleading. Evaluate decoding support, metadata, transparency, color, timing, patents, and archival needs before choosing an output.
Key facts
- 1RGBE allocates one byte to each color component and one shared exponent to the pixel. Channels with very different magnitudes therefore do not receive independent floating-point precision.
- 2The resolution string also states axis order and direction. A decoder that extracts only width and height can transpose or flip files whose orientation differs from its assumption.
- 3Radiance HDR has no alpha channel in its standard RGBE pixel representation. Transparency or masks must travel separately or be carried by another working format.
When Radiance HDR matters
Use Radiance HDR for lighting environments, rendering pipelines, or image-based illumination that requires a broad luminance range. Convert carefully when a destination lacks RGBE support or applies incompatible color handling.
- Accepting heterogeneous uploads while producing a controlled set of delivery formats.
- Moving assets between cameras, editors, browsers, archives, and downstream APIs.
- Separating long-lived source files from compact derivatives optimized for a particular channel.
Working with file formats at scale
Guidance that holds across every file formats term in this glossary, not just Radiance HDR.
What you gain
- A suitable format preserves the properties a workflow actually needs.
- Standardized structures allow files to move between compatible tools and systems.
- Format conversion can improve delivery size, editability, or long-term accessibility.
What it costs
- Modern formats can save bandwidth but may need fallbacks for older clients and production tools.
- Converting to a simpler format can discard transparency, animation, metadata, color precision, or editability.
- Archival suitability, browser support, and editing support often favor different choices.
Answer these before production
- 1Inspect the detected container, codec, MIME type, and magic bytes instead of trusting a suffix.
- 2Verify decoder support and preserve metadata, color, transparency, or timing when required.
- 3Retain the source when the chosen delivery format is lossy or tied to current software.
How Transloadit helps with Radiance HDR
When Radiance HDR is relevant to your workflow, you can hand the surrounding file formats work to Transloadit instead of maintaining the processing stack yourself. Transloadit detects file and MIME information, filters inputs, and converts images, audio, video, and documents into formats suited to browsers, applications, archives, and downstream services.
Support for a specific codec, container, parameter, or combination can vary by Robot and processing stack. Check the linked documentation for the exact inputs and outputs available for your use case.