Preserving original metadata tags & indicating that tags have been changed

[KingsCross]

ExifTool newbie here...

I am planning on adding EXIF date/time information using

exiftool "-alldates<filemodifydate"

I'm wondering what the best way is to preserve the original file modification date? Or perhaps preserve all the original metadata tags for future reference?

Similarly, is there a recommended method for indicating that the EXIF data was manually entered/calculated, rather than applied by the camera when the image was shot? Essentially, I want to make sure that I can figure out which photos had the metadata applied/edited after the fact.

Thanks.

[StarGeek]

I'm wondering what the best way is to preserve the original file modification date?

Take a look at the -P (preserve) option.

Or perhaps preserve all the original metadata tags for future reference?

Not within the file itself.   You can take a look at the Metadata Sidecar Files page for some external options.  Specifically the "EXIF Files" section for EXIF data or the "MIE Files" for all metadata.  Also exiftool will automatically create a backup of any file unless the Overwrite_Original option is used.

Similarly, is there a recommended method for indicating that the EXIF data was manually entered/calculated, rather than applied by the camera when the image was shot? Essentially, I want to make sure that I can figure out which photos had the metadata applied/edited after the fact.

None that I've heard of.  It's pretty much something you would keep track of it yourself somehow.