You could try ExifTool to delete tags, but you will be shooting in the dark as you won't really know what Vuescan considers to be pristine.
But I don't understand your comment about not wanting to process the DNGs in LR or ACR. So far as I am aware, both process all DNGs, raw or not, just fine.
Thank you for your answer. I ll give it a try.
The reason you don't want to process vuescan dng's in ARC/LR is that these dng's are rendered files as opposed to real raw files which have te be demosaiced in the raw converter.
Vuescan dng's behave much like a tiff, but they are untagged and ACR/LR assumes sRGB when the file is opened and with all under the hood conversions the result is not what you would get if you open proper tagged TIFFs.
I remember Andrew Rodney explaining this very clearly but unfortunately i m not able to recall where i once read it.
Vuescan dng's behave much like a tiff, but they are untagged and ACR/LR assumes sRGB when the file is opened and with all under the hood conversions the result is not what you would get if you open proper tagged TIFFs
Not the case any version of LR or ACR I know of. E.g. pcdMagic creates linear DNGs in what is the equivalent of the ProPhoto space, and LR/ACR reads them fine. (I say "equivalent of" because DNG files don't have tags in the sense that TIFF does, but you can implicitly set the primaries, etc just as you would in a color space tag).
I think I may have found what seems to be at the root of the problem.
Apparently Vuescan writes and reads 1.1 DNG's.(according toExifTool). As soon as such a file is edited in ACR/LR a new DNG (1.3) is written. This 1.3 spec DNG is only opened in Vuescan as its preview (small size @ 300 dpi).
Unless there is a way to revert a 1.3 DNG to a 1.1 DNG I am stuck. I already tried to use the DNG converter to use a custum setup to have it write DNG 1.1 uncompressed.
But still no luck, Exif tool reports they still are 1.3 DNG's.