File extension .EXR refers to the OpenEXR format supported by ImageConverter Plus. The EXR image format is notable for a higher dynamic range and tight color precision. The EXR format is also known for multiple lossless image compression algorithms. The default compression algorithm is RLE. It is based on the idea to replace a long sequence of the same symbol by a shorter sequence and is a good introduction into the data compression field for newcomers. Other compression algorithms include:
Zip (per scanline)—Zip-style compression applied to individual scanlines
Zips (16 scanline blocks)—Zip-style compression applied to blocks of 16 scanlines at time. This tends to be the most effective style of compression to use with rendered images that do not have film grain applied
PIZ ( wavelet compression )—Uses a combined wavelet/Huffman compression. This form of compression is best for grainy images
PXR24 – resulting files are compressed with PXR algorithm. It was created for working with professional 3D animations on Pixar high-end graphics stations. Peculiarities of this algorithm are: absence of compression, support for RGB, grayscale and alpha-channel.