2004.09.15 23:24 "Re: [Tiff] Removing reduced resolution pages", by Han The Man
0x03 means the file has the FILETYPE_REDUCEDIMAGE *and* the FILETYPE_PAGE flags set for the subtype. This suggests that some of the IFDs in the file will be additional pages, and some will be reduced resolution versions (presumably of the preceeding non-reduced resolution image).
Thanks... it's just a logical OR-ing of subtypes. Makes sense.