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RAF files from older 16-megapixel X-trans cameras are about 30MB. Compressed RAF files from newer 24-megapixel cameras are about 20MB. Given the size savings, it would be nice if uncompressed files could be converted into the compressed format. How can this be done?

Compression using conventional file compression algorithms cuts the file size approximately in half. However, such files cannot be previewed or processed without decompression.

File-system level compression is not helpful because it is not supported by all file systems. It also still suffers from effects of large file sizes, such as reduced transmission speeds.

Although DNG supports compression, the X-trans sensor layout and color balance are not well preserved after conversion to DNG. DNG allows the original raw to be embedded to work around such issues, but doing so eliminates any potential compression size savings.

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When converting RAF to DNG, absolutely identical data is stored in both RAF and DNG. "Preserve demosaicking" makes no sense, as there is no demosaicking inside RAW photos. Demosaicking method can be applied to RAF file just as well as to DNG file, and give the same result.

You should be able to create compressed DNGs, too, which should be even smaller than compressed RAFs.

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    1. This doesn't answer the question because I want compressed RAF, not DNG. 2. Last time I tried converting RAF to DNG, the X-Trans sensor layout confused the Adobe software so that demosaicking did not work at all. It appeared to be interpreting the data using a Bayer layout, so it was the X-Trans layout that was not preserved during demosaicking. 3. "absolutely identical data" – This is not the case. Otherwise, they would be "absolutely identical" file formats, and no conversion would be necessary. It's not even possible to reverse conversion to dng without embedding the original raw. – xiota Jun 25 at 1:28
  • I am not aware of all possible ways of converting RAF to DNG. Maybe you just need to try a different program, or report a bug to developers of your program. What I wanted to say, is, that it is possible to store identical data (values of samples, X-Trans pattern information and all other parameters) in a DNG file instead of RAF. – Ivan Kuckir Jun 25 at 7:43
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    "it is possible to store identical data... in a DNG file instead of RAF" – That's the party line, but it's obviously not true because the conversion is irreversible, unless you embed the full RAF, in which case the DNG ends up larger than the original. // You're basically trying to sell aspirin to someone who's already told you they prefer acetaminophen because they're allergic to aspirin. – xiota Jun 25 at 7:50
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    So your solution is pay Adobe to make my life harder? No. – xiota Aug 2 at 9:08
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    DNG = Adobe format. It's about as "open" as Microsoft Office Open XML. Since it was "standardized", it's gone through multiple proprietary revisions. – xiota Aug 2 at 9:25

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