HDR to EXR: conversion guide

What happens when you convert HDR to EXR?

HDR working data

HDR and EXR can represent values beyond ordinary display white, but use different sample encodings. Conversion needs colour and numeric-range mapping; supported channels and precision may differ. In particular RGBE does not carry EXR alpha, arbitrary auxiliary channels, multipart or deep structures. The future engine defines the mapping.

Transparency

The target can store an alpha channel, but converting an opaque image does not create transparent areas. Removing a background is a separate editing step.

Encoding mode

EXR supports lossy and lossless codecs. Choose one for the sample types and required precision; .exr alone does not guarantee exact channel preservation. EXR permits different encoding modes or container representations. Its format name alone does not promise lossless output, a quality setting or a size reduction. The future engine must choose a supported codec and sample representation; inspect the target’s compression notes below.

HDR

Source

HDR

Radiance HDR / RGBE

Compression: LosslessTransparency: NoMetadata: Radiance header, EXPOSURE, FORMAT

Radiance pictures with a shared exponent for high-dynamic-range lighting values.

Explore HDR format →

EXR

Target

EXR

OpenEXR

Compression: Lossy & losslessTransparency: YesMetadata: Typed header attributes, Chromaticities

HDR raster data for rendering and compositing, with named channels and lossless or lossy codecs.

Explore EXR format →

Is HDR → EXR right for you?

Good choice when

EXR fits your delivery use: Render passes & HDR compositing.
Your pipeline needs an HDR-capable rendered working image.
Your receiving application supports the required EXR variant.
You can validate the destination’s sample precision and colour interpretation.
You need a EXR-compatible workflow that can hold transparency added in a separate edit.

Probably not when

You require identical floating-point values or every source channel.
You need a guaranteed quality or file size before encoder settings exist.
You require identical samples without a defined colour and precision policy.
You expect automatic background removal or transparency.

HDR to EXR conversion details

HDR working data: HDR and EXR can represent values beyond ordinary display white, but use different sample encodings. Conversion needs colour and numeric-range mapping; supported channels and precision may differ. In particular RGBE does not carry EXR alpha, arbitrary auxiliary channels, multipart or deep structures. The future engine defines the mapping.
Transparency: The target can store an alpha channel, but converting an opaque image does not create transparent areas. Removing a background is a separate editing step.
Encoding mode: EXR supports lossy and lossless codecs. Choose one for the sample types and required precision; .exr alone does not guarantee exact channel preservation. EXR permits different encoding modes or container representations. Its format name alone does not promise lossless output, a quality setting or a size reduction. The future engine must choose a supported codec and sample representation; inspect the target’s compression notes below.
Sample precision & colour: Source and target sample models can differ in precision, channel layout, colour space and transfer function. Lossless compression only preserves the samples actually encoded; a precision reduction or colour conversion can already change them. The future engine defines numeric mapping, orientation and colour conversion; canonical depth facts are listed below where available.
Metadata & colour: Format support does not guarantee that an export preserves metadata or colour profiles. Retention and colour handling depend on the future converter; its engine is not implemented yet.
Compression: HDR: Lossless → EXR: Lossy & lossless HDR: RLE preserves stored RGBE bytes; RGBE quantization is not exact storage of arbitrary float RGB. The .hdr format is distinct from the general concept of HDR photography. EXR: EXR supports lossy and lossless codecs. Choose one for the sample types and required precision; .exr alone does not guarantee exact channel preservation.
Transparency: HDR: No → EXR: Yes
Colour depth: HDR: 32-bit RGBE / XYZE pixel → EXR: HALF 16 / FLOAT 32 / UINT 32
HDR: HDR: Radiometric values → EXR: Floating-point working values
Multiple images: EXR: Multipart
Dimensions: Pixel dimensions, page geometry, rendering resolution, resizing and orientation need explicit converter policies. The future engine has not defined them yet.
Metadata: HDR: Radiance header, EXPOSURE, FORMAT → EXR: Typed header attributes, Chromaticities. Which fields are copied, rewritten or omitted will depend on the future engine; retention is not implemented yet.

Common questions

Does HDR-to-HDR mean every channel survives?

HDR and EXR can represent values beyond ordinary display white, but use different sample encodings. Conversion needs colour and numeric-range mapping; supported channels and precision may differ. In particular RGBE does not carry EXR alpha, arbitrary auxiliary channels, multipart or deep structures. The future engine defines the mapping.

Will the background become transparent?

The target can store an alpha channel, but converting an opaque image does not create transparent areas. Removing a background is a separate editing step.

Which compression mode will EXR use?

EXR supports lossy and lossless codecs. Choose one for the sample types and required precision; .exr alone does not guarantee exact channel preservation. EXR permits different encoding modes or container representations. Its format name alone does not promise lossless output, a quality setting or a size reduction. The future engine must choose a supported codec and sample representation; inspect the target’s compression notes below.

Are bit depth and colour values guaranteed to match?

Source and target sample models can differ in precision, channel layout, colour space and transfer function. Lossless compression only preserves the samples actually encoded; a precision reduction or colour conversion can already change them. The future engine defines numeric mapping, orientation and colour conversion; canonical depth facts are listed below where available.

Will metadata and colour profiles be retained?

HDR: Radiance header, EXPOSURE, FORMAT → EXR: Typed header attributes, Chromaticities. Which fields are copied, rewritten or omitted will depend on the future engine; retention is not implemented yet.

Explore related HDR and EXR conversions.