The CR2 takes over from Canon's previous format - CRW and is used by the Canon 350D, 1D, G9 and 20D models. RAW files are the best quality to size ratio that a photograph can be stored in, primarily because each colour is recorded in either 12 or 14 bits and a lossless compression is used. You can choose to store your pictures in RAW format which gives you the benefit of being able to do a lot of post processing on the file, if you tried to do this with JPEG, this would be difficult and would likely result in a quality loss. This does not contain a ready to view picture like a JPG or PNG file, it is used to store information directly coming from the sensor. Compression rates of 10:1 or 20:1 yield little degradation in image quality.The Canon RAW version 2 (cr2) format is a RAW format created by Canon for storing digital images. Compression rates of 100:1 can be achieved, although the loss is noticeable at that level. JPEG involves a lossy compression mechanism using discrete cosine transform (DCT).
JPEG is a joint standard of the International Telecommunications Union (ITU-T T.81) and the International Organization for Standardization (ISO 10918-1). JPG is a graphical file format for editing still images, it offers a symmetrical compression technique which is processor intensive and time consiming in both compression and decompression. The JPG file is a great format as it often manages to compress files to 1/10 of the size of the original file which is especially good for saving on bandwidth. The JPG format is often used in digital camera memory cards. The resultant 'lossy' file means that quality can never be recovered. JPG's are often used for web sites and email as they are generally smaller file sizes as they are lossy meaning that some image quality is lost when the JPG is compressed and saved.
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