Hi Phil, I'm a newbie here, but I use your tool (with exiftoolgui) since 2010. I have a question that is more a curiosity rather than a concern.
I formerly used your tool for geotagging and now sometimes to shift the date.
Using a compare software I noticed that when you do an edit like this, the file structure changes, as you can see from the attached picture. Some sections of apparently the same size, are shifted forward or backward.
Can you explain me why? And can you assure me that this keeps the compatibility with other softwares?
Many thanks
See FAQ 13 (http://www.exiftool.org/faq.html#Q13).
As long as the other software is written correctly, the new file should be compatible. With regular tag blocks like EXIF, IPTC, and XMP, it's extremely unlikely that there would be any problem with major software.
I've used exiftool for quite a few years now and it's the only piece of software that I trust completely with the writing of metadata. Nearly every other software I've tested screws something up at some point.
Thanks StarGeek. I trust exiftool too and most of all the main point of this thread was technical, why a slightly bit different structure.
Yes, FAQ 13 explains this as StarGeek mentioned.
What the FAQ doesn't say is that ExifTool writes the EXIF/TIFF format using the cleanest, most straightforward structure possible, with strict adherence to the specification and no additional junk or empty spaces. If everyone did this then the file structure wouldn't change when edited by ExifTool. ;)
- Phil
Edit: Oh, except that I just took a look at your compare.png file. When Adding metadata, the structure will necessarily change to make room for the new entry in the TIFF IFD, and all embedded offsets must be adjusted since the value data will move. It may make more sense if you look at this with the exiftool -htmldump feature to understand the structure a bit more (and reading the TIFF spec wouldn't hurt either).