Choosing Metadata Tags - XMP, EXIF, IPTC

[Cici]

Hi, New here. I have thousands of scanned historical images and documents. I have Raw DNG Files, Raw TIF files, regular TIF files, JPGs and PDFs. I store my files in OneDrive and access them via my MacBook. I also plan to load the JPGs in Apple Photos. I would like to use the ExifTool by referencing a csv file to assign historical dates (XMP-exif:DateTimeOriginal/XMP-exif:DateTimeDigitized), captions (XMP-dc:Description), keywords (XMP-dc:Subject), GPS DateTime (XMP-exif:GPSDateTime), GPS latitudes (XMP-exif:GPSLatitude) and GPS longitudes (XMP-exif:GPSLongitude) to my images. And for the PDFs, Original Document Date (XMP-pdf:CreationDate), Subject (XMP-pdf:Subject), and Keywords (XMP-pdf:Keywords).  To keep it simple, I was hoping to use XMP tags for all file types. If I am reading the documentation correctly, it doesn't appear that XMP-exif dates support time zone offsets, so that could change my approach. Is there any other reason that I should use EXIF or IPTC tags in addition to XMP tags? Appreciate any guidance or suggestions. Thanks.

[Alan Clifford]

My xmp dates have a time zone, for example

exiftool -a -G1 -*date* x-s1_4665.jpg

Code Select Expand

[System]        File Modification Date/Time     : 2024:02:22 18:40:48+00:00
[System]        File Access Date/Time           : 2024:04:18 19:24:11+01:00
[System]        File Inode Change Date/Time     : 2024:04:18 17:59:46+01:00
[IFD0]          Modify Date                     : 2024:02:21 21:08:35
[ExifIFD]       Date/Time Original              : 2024:02:19 15:35:44
[ExifIFD]       Create Date                     : 2024:02:19 15:35:44
[GPS]           GPS Date Stamp                  : 2024:02:19
[XMP-exif]      Date/Time Original              : 2024:02:19 15:35:44+02:00
[XMP-exif]      GPS Date/Time                   : 2024:02:19 13:35:44
[ICC-header]    Profile Date Time               : 2009:02:20 17:07:10
[Composite]     Date/Time Original              : 2024:02:19 15:35:44+02:00
[Composite]     GPS Date/Time         

Phil's documentation has a link to the standard that says iso 8601 format is used for xmp dates.

[Cici]

Thanks Alan. That's good news. I was looking at the documentation late last night instead of the actual value.

[StarGeek]

If I am reading the documentation correctly, it doesn't appear that XMP-exif dates support time zone offsets, so that could change my approach.

You are not. As Alan says, the the time zone (as well as subseconds) are included.  From FAQ #5

The standard EXIF date/time format is "YYYY:mm:dd HH:MM:SS", and some meta information formats such as XMP also allow sub-seconds and a timezone to be specified.

Is there any other reason that I should use EXIF or IPTC tags in addition to XMP tags? Appreciate any guidance or suggestions. Thanks.

IPTC can be ignored. For date/time and GPS tags, then EXIF probably should be used, as many programs will give them priority and some won't even read GPS data that appears only in XMP.

[StarGeek]

Phil's documentation has a link to the standard that says iso 8601 format is used for xmp dates.

I believe the ISO format uses dashes between the dates, while exiftool uses the EXIF specs format of colons and converts it behind the scenes. But this usually doesn't prevent using the ISO format because of FAQ #5.

[Cici]

Thanks StarGeek. I was trying to learn ExifTool while I was incredibly tired and sleepy. Not the best idea. I see I was reading the documentation incorrectly. Thanks for referring me back to FAQ #5. I also reviewed the ISO 8601 format. Thanks for the suggestion to use EXIF as well as XMP. Definitely an ExifTool novice, but I'm getting the hang of it. Successfully updated my image files using a CVS file and also exported the image files metadata into a CSV file. Love ExifTool.