With the release of Star Wars Episode III this week, I thought it would be fitting to review a file format that was used in the production of it. Industrial Light and Magic, the company founded by George Lucas for the special effects of the original Star Wars Trilogy, has become one of the leading special effects and post production companies in the world. The OpenEXR image format was pioneered by ILM so that a standard format could be used in their movies. It was first used on the first Harry Potter movie, and is currently used in all productions ILM takes part in. OpenEXR can be downloaded here: http://www.openexr.com.
Before getting into the technical detail of the program itself, it would be useful to know why the format is necessary. OpenEXR is a format developed to make visual effects better, but can also be useful in the home. Conventional 8, 10, and 16 bit image formats do not have the quality that is necessary for high-resolution images, while 32 bit TIFF (raw) images have the features, but lack the economical ability of regular 16 bit formats – a typical TIFF image can range anywhere from a few megabytes through a few gigabytes, depending on its size. This is not a practical use for either home or commercial users. OpenEXR was developed to create a format between 16 bit and 32 bit formats, as well as having sufficient quality for effects work, and being economical. Thus, OpenEXR was developed, and it bridges the gap amazingly well.
OpenEXR can be downloaded either in C++ libraries to program into your own image editor, or as an Adobe Photoshop plug-in. The former is for developers and production studios, while the latter is for end users.
The Photoshop element is extremely easy to install and use. It allows you to open an EXR file in Photoshop, as well as edit and save the file in the EXR format. The main function of the EXR format is to adjust the exposure (brightness) and the gamma (whitepoint) of the image to increase detail. It is very useful when a picture is either too light or too dark, and allows you to see things that normally wouldn’t be visible, as well as improve the overall quality of the image.
The above image is the original file at 0 exposure and 2.2 gamma (standard). You can faintly see the background circles in the image, but can see the white square in the middle.
The above image is the same one at a darker exposure level of -7 and a standard gamma. You can now see the background circles, and no longer see the white square in the middle.
In the above image, whose settings are at a -7 exposure and a -4 gamma, you can see a black square, and the colored circles both at the same time.
Its amazing to see how much detail can be lost by a generic save – and how much detail can be obtained by altering it with an EXR format. Overall, the program is highly useful, but not very user friendly. It requires some effort to figure out, but once you have it figured out, you can do a lot of very neat things with it. I am amazed that such a cool program can be released under an open source license!
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