TIFF tags

[MOL]

Phil, do you happen to know of a good overview of where Baseline, Extension and Private TIFF tags end up when written to an image? It seems they are all over the place (mainly in the EXIF, XMP and IPTC sections), but I can't find anything regarding this topic on your web site.

http://www.digitalpreservation.gov/formats/content/tiff_tags.shtml


Thanks!

[Phil Harvey]

Hi MOL,

I'm not sure exactly what you are asking, but does this help? (under "Group Priorities" on the ExifTool home page):

ExifTool prioritizes the following types of meta information when writing:

1) EXIF,   2) IPTC,   3) XMP

Many tag names are valid for more than one of these groups. If a group name is not specified when writing information, then the information is added only to the highest priority group for which the tag name is valid (however, the information is updated in all groups where the tag already existed). The priority of the groups is given by the list above. Specifically, this means that new information is added preferentially to the EXIF group, or to the IPTC group if no corresponding EXIF tag exists, or finally to the XMP group.

For tags written to the EXIF group, the EXIF Tag Name documentation lists the IFD where they will be written.

- Phil

[MOL]

Thanks, Phil. To be honest, I wasn't too sure what I was asking either. 

I did some testing the other day with Canon's ZoomBrowserEx software and added a user comment to a regular TIF file. Under normal circumstances - writing to CRW, CR2 or JPG files that is - the program places the user comment into the EXIF section of the image. Not so with the TIF file. The comment is nowhere to be found, although ZoomBrowserEx displays the image and the associated comment correctly every time. I then ran the image through ExifTool, but to no avail. That's why I was wondering about the TIFF tags and where they are written.

[Phil Harvey]

If ExifTool can't find the information stored by ZoomBrowser, it could be that it is maintaining a separate database.  Check the size and timestamps of the file before and after saving a user comment.  If the file really changes, send me a copy by email and I will see if I can find where it was stored (philharvey66 at gmail.com).

I don't have ZoomBrowser, but I tried DPP and ImageBrowser but neither could write a comment.

- Phil

[MOL]

Good catch, Phil. ZoomBrowserEx seems to maintain its own database somewhere (haven't found it yet), but only for formats other than CRW, CR2 and JPG. After adding a comment, I moved the TIF file to another folder and reopened it in ZoomBrowserEx. The comment was gone.

Thanks again
Uwe