The extra tags represent information found in the image but not associated with any other tag group. The three writable "pseudo" tags (Filename, Directory and FileModifyDate) may be written without the need to rewrite the file since their values are not contained within the file data.
Tag Name Writable Values / Notes CanonVRD N (the full Canon DPP VRD trailer block) Comment Y (comment embedded in JPEG, GIF89a or PPM/PGM/PBM image) Directory Y! EXIF N (the full EXIF data block) Encryption N Error N ExifByteOrder Y (only writable for newly created EXIF segments)
'II' = Little-endian (Intel)
'MM' = Big-endian (Motorola)
ExifToolVersion N FileModifyDate Y (the filesystem modification time) FileName Y! FileSize N FileType N ICC_Profile Y! (the full ICC_Profile data block) ImageHeight N ImageWidth N MIMEType N MaxVal N Warning N XMP Y (the full XMP data block) XResolution N YResolution N
<-- ExifTool Tag Names