What Is the HDR Image Format?

Radiance HDR came out of Greg Ward's Radiance renderer in 1985 and was the first widely used way to store real luminance values rather than display-referred pixels. Its RGBE encoding packs an enormous dynamic range into 32 bits per pixel, which is why it remains the standard container for environment maps and image-based lighting in Blender, Maya, Unreal and every other 3D pipeline.

Compression: RGBE — shared exponent per pixel. Transparency: Not supported. Animation: Not supported. Colour: Floating-point, effectively unlimited dynamic range. Typical file size relative to WebP: much larger than WebP.

3D renderers, VFX and photographic HDR tools. This is usually the deciding factor when choosing between HDR and WebP — WebP renders in every browser but is uneven in desktop software, while HDR has a very different support profile.

HDR files cannot be displayed by browsers or ordinary viewers. Converting to WebP tone-maps the image down to something you can actually look at and share. WebP is an 8-bit display-referred format. Converting from it cannot create dynamic range that was never captured — the result is a valid .hdr file but not a true high-dynamic-range capture.

3D and VFX pipelines want .hdr for environment maps and image-based lighting. This wraps your image in that container so it drops into Blender, Maya or Unreal as a light source. Expect the HDR output to be much larger than WebP — that difference is the price of getting a format the destination will actually accept.