- published: 04 May 2014
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OpenEXR is a high dynamic range imaging image file format, released as an open standard along with a set of software tools created by Industrial Light and Magic (ILM), released under a free software license similar to the BSD license.
It is notable for supporting 16-bits-per-channel floating point values (half precision), with a sign bit, five bits of exponent, and a ten-bit mantissa. This allows a dynamic range of over thirty stops of exposure.
Both lossless and lossy compression of high dynamic range data is also supported.
For a full technical introduction of OpenEXR, see the Technical Introduction available on the OpenEXR.org website.
OpenEXR, or simply EXR for short, is a deep raster format developed by ILM and very broadly used in the computer-graphics industry, both visual effects and animation.
OpenEXR's multi-resolution and arbitrary channel format makes it appealing for compositing. OpenEXR alleviates several painful elements of the compositing process. Since it can store arbitrary channels, specular, diffuse, alpha, RGB, normals, and various other types of channels in one file, it takes away the need to store this information in separate files. The multi-channel concept also reduces the necessity to "bake" in the aforementioned data to the final image. If a compositer is not happy with the current level of specularity, he or she can adjust that specific channel.