What is a tag family?

[Wayne]

I've used ExifTool for a few years now, but one concept that still escapes me, and that I can't seem to find an explanation for, is tag families. I understand tag groups (XMP, EXIF, etc), or, at least, I think I understand tag groups, haha. But I can't seem to wrap my head around the family concept. Would someone mind explaining that? TIA

[Phil Harvey]

It is not a family of tags, but a family of groups.

XMP and EXIF are family 0 groups.

For example, family 2 has groups like Time, Preview and Location.

See here for a list of groups in each family.  The different families contain groups that classify the tags in different ways.

I hope this make sense.

- Phil

[Wayne]

I don't have a strong enough understanding of the file structures (how the metadata is actually stored in the files) to fully grasp what the documentation is saying, but the link you posted, and the 'GetGroup()' function documentation that it links to, were exactly what I was looking for, and I get the general idea, so thank you. Maybe one day I'll have the time to study the inner workings of how metadata is actually stored so that I can gain a deeper understanding.

BTW, ExifTool absolutely rocks. Thank you.

[Wayne]

For anyone else that may have this same question in the future, I was playing around trying to gain a better understanding of this concept and had an "Aha!" moment. Check out these commands and compare their output, keeping in mind what Phil (and his documentation) said:

Code Select Expand


exiftool -EXIF:DateTimeOriginal -G0 -s IMG_5128\ 7.12.47\ AM.jpg
[EXIF]          DateTimeOriginal                : 2020:06:11 18:49:18

exiftool -EXIF:DateTimeOriginal -G1 -s IMG_5128\ 7.12.47\ AM.jpg
[ExifIFD]       DateTimeOriginal                : 2020:06:11 18:49:18

exiftool -EXIF:DateTimeOriginal -G2 -s IMG_5128\ 7.12.47\ AM.jpg
[Time]          DateTimeOriginal                : 2020:06:11 18:49:18

exiftool -EXIF:DateTimeOriginal -G0:1 -s IMG_5128\ 7.12.47\ AM.jpg
[EXIF:ExifIFD]  DateTimeOriginal                : 2020:06:11 18:49:18

exiftool -EXIF:DateTimeOriginal -G2:0 -s IMG_5128\ 7.12.47\ AM.jpg
[Time:EXIF]     DateTimeOriginal                : 2020:06:11 18:49:18

exiftool -EXIF:DateTimeOriginal -G2:0:1 -s IMG_5128\ 7.12.47\ AM.jpg
[Time:EXIF:ExifIFD] DateTimeOriginal            : 2020:06:11 18:49:18