Radiance HDR Image (.HDR)
HDR (High Dynamic Range) Radiance format, also known as RGBE, stores images with a high dynamic range of luminance values using a run-length encoded format. Developed by Greg Ward for the Radiance lighting simulation system, it encodes each pixel as three 8-bit mantissas and a shared 8-bit exponent. HDR images capture a much wider range of brightness than standard 8-bit formats.
Advantages of Radiance HDR Image
What the HDR format does well, and why you might choose it.
- Captures a wide dynamic range of lighting from very dark to very bright
- Relatively compact encoding for high dynamic range data
- Widely supported in 3D rendering, game engines, and compositing software
Limitations of Radiance HDR Image
What the HDRformat doesn't do well, and when to choose another format.
- Lower precision than 32-bit EXR for demanding visual effects work
- Not suitable for direct display without tone mapping
- Limited to RGB data with no alpha channel support
What HDR files are used for
- Environment maps and image-based lighting in 3D rendering
- HDR photography merging and tone mapping workflows
- Lighting simulation and architectural visualization
How HDR files work
Raster images are grids of pixels, each carrying color information. The format determines how those pixels are stored: lossless formats (PNG, TIFF, BMP, WEBP-lossless) preserve every pixel exactly, lossy formats (JPG, WEBP, AVIF, HEIC) discard imperceptible detail to shrink the file. Color depth (8-bit, 10-bit, 16-bit), color profile (sRGB, Display P3, ProPhoto), alpha channel support, and metadata (EXIF, IPTC, XMP) all vary by format. Modern web formats like AVIF and WEBP build on improvements in video compression to deliver dramatically smaller files at equivalent quality versus JPG and PNG.
Best practices when working with HDR
Photographs compress well as JPG or AVIF; graphics with sharp edges, text, or transparency belong in PNG or WEBP-lossless. Never re-save a JPG repeatedly — every save adds compression artifacts. Strip EXIF metadata before publishing photos publicly if you don't want GPS coordinates and camera serial numbers exposed. For print, deliver in TIFF at 300 DPI; for screen, JPG/WEBP at 72-100 DPI is plenty. If you're optimizing for the web, AVIF beats WEBP beats JPG on file size, but JPG still has the broadest support.
Convert to HDR
The most common formats people convert to HDR, ready to convert in seconds.
Convert HDR to other formats
Convert Radiance HDR Image files into the format you actually need.
Choosing HDR versus the alternatives
JPG: photographs, social media uploads, anywhere universal compatibility matters. PNG: graphics with text, line art, screenshots, or transparency. WEBP: modern web replacement for JPG and PNG with better compression. AVIF: best-in-class web compression, growing browser support. TIFF: print and archival masters. BMP: rarely the right answer in 2026 — uncompressed and uniform-poor versus PNG. HEIC: efficient mobile photo capture, but limited compatibility outside Apple's ecosystem.
Where HDR fits in real workflows
Most image workflows have a master file (PSD, RAW, TIFF) that you keep forever and never publish, plus delivery exports (JPG, WEBP, AVIF) generated for each context where the image appears. Treat published files as derivatives — if quality requirements change, regenerate from the master rather than re-converting an already-compressed version.
Privacy and file handling
When you convert a HDRfile with MegaConvert, the file is uploaded to our converter, processed, and automatically deleted within an hour. We don't train models on your files, share them with third parties, or retain them after the conversion completes. The download link expires when the file is removed. If your work involves files subject to NDA or compliance requirements (HIPAA, GDPR data processing), please review our privacy policy before uploading sensitive material.
Frequently asked questions about HDR
What is a .HDR file?
HDR (High Dynamic Range) Radiance format, also known as RGBE, stores images with a high dynamic range of luminance values using a run-length encoded format. Developed by Greg Ward for the Radiance lighting simulation system, it encodes each pixel as three 8-bit mantissas and a shared 8-bit exponent. HDR images capture a much wider range of brightness than standard 8-bit formats.
What is the MIME type of HDR?
The official MIME type for HDR files is image/vnd.radiance. This is the value web servers and applications use to identify the format when transferring files.
What category does HDR belong to?
HDR is a Image Converter format. Files in this category share common conversion paths and use cases.
How do I open a .HDR file?
HDR files are typically opened by software that natively supports the Radiance HDR Imageformat. If you don't have a compatible application, the most reliable approach is to convert the file to a more universal format using the converters listed above. Most Radiance HDR Image files convert to widely-supported alternatives in seconds.
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