The value of raw files in the process of Cultural Heritage Digitization is enormous. As described in the Standard Raw Digitization Workflow, it can significantly increase productivity compared to direct-to-TIFF workflows. However, the raw itself is not generally considered to be a Preservation Digital Object. No two raw processing programs will render a particular raw file identically, and even different versions/generations of the same raw processing program will render a particular file with subtle, but non-trivial, differences.
There is often value to maintaining a short/mid term archive of the raw files used to create the PDOs in a collection. For instance, between Capture One v3, v4, v6, v7, and v8, there were significant and continuous improvements to the amount of real detail that could be extracted from a given raw file which yielded tangible increases in numerically measured sampling efficiency and perceived visual fidelity; this improvement was due to improved algorithms in the software. These benefits could only be seen when reprocessing the original raw file, so institutions that only had processed derivatives like TIFFs missed out on this gain in quality.
Given these improvements in raw processing, it makes sense to retain raw files for months or even years. However, a raw file does not stand alone – specific software is required to convert it into a useful image; the same raw file, opened in different (or future) software changes the way the image appears. So in the scope of decades and centuries, the raw file should not be considered a preservation object.
There is also some value to having the raw files in the short-term and mid-term as a low-storage-cost emergency backup of the PDO TIFFs/JPG2000 files.
“In 2014, six months into a massively expanded digitization effort, we had a significant failure in our primary storage system. Since the expanded digitization program was just ramping up and our off-site emergency backup solution had not yet been finalized, some portion of our work was lost. Fortunately our IT department had provided us with separate storage for a raw file archive; I insisted we carry over the film-era practice of keeping your negatives. Reprocessing these raw files to TIFF meant we did not lose any work. It really saved our bacon.”
– Brad Flowers, Dallas Museum of Art