HDR Image Formats

Pixar's Log Format

Pixar has recognized the need for dynamic range in film recording, so they developed a 33-bit/pixel log encoding for RGB values, which is implemented as part of Sam Leffler's TIFF library. The encoding covers about 3.5 orders of magnitude, with 0.4% relative accuracy.


Since it's inception in 1987, the RADIANCE rendering system has used a 32-bit/pixel floating point format. The image format is described on the RADIANCE web site. The encoding covers about 76 orders of magnitude with 1% relative accuracy.

SGI's LogLuv Format

Sam Leffler's TIFF library includes a codec for a 32-bit/pixel logLuv encoding. Compared to the RADIANCE and Pixar encodings, this has the advantage of covering the full gamut of perceivable colors in imperceptible steps. The luminance range covers 38 orders of magnitude with 0.3% relative accuracy, and chroma errors never reach the visible threshold.

Industrial Light and Magic's OpenEXR

The file format was developed to overcome the limited dynamic range and colour precision in computer imaging applications. The specifications were published under an Open Source license, software and libraries are available under a modified BSD license.

IEEE 96 bit TIFF and Portable FloatMap

Info goes here...


The JPEG-HDR file format was developed by Greg Ward to be backward compatible with existing software. It create very small files sizes.


Format Dynamic Range Accuracy Bits/pixel
RADIANCE RBGE 76 1.0% 8R + 8G + 8B + 8E
Pixar Log TIFF 3.8 0.4% 11R + 11G + 11B
LogLuv 24-bit 4.8 1.1% 10logL + 14(u',v')
LogLuv 32-bit 38 0.3% 16logL + 2x8(u',v')
ILM OpenEXR 9.6 0.1% 16R + 16G + 16B
TIFF 48-bit 5.4 1.0% 16logR + 16logG + 16logB
IEEE TIFF 96-bit 79 32R + 32G + 32B