which EXIF fields to write in RAW data

[lbo]

Hi all,

as I'm considering to change my metadata storage from embedding in RAW files to sidecar files, I wonder which kind of information shall be written to RAW files at all.

https://www.photools.com/help/imatch/#md_storage.htm mentions the "never modify a RAW file" policy and this seems to be a good idea.

In the default setting, IMatch writes several entries to CR2 files:

• "Description" to EXIF Image Description and EXIF User Comment
• Timezone offset
• IFD1 resolution

Wouldn't it be more consistent to update ("correct") only the existing EXIF information, e.g. timezone?

What is the benefit / reason to write the other entries?

If I interpret correctly, MWG doesn't require to write not yet existing EXIF fields:

Upon writing Exif metadata, a Changer MUST update all formats that were originally present in the file.
If not all of the formats were originally present, a Changer MAY choose to write the complete set.

But this wording is somewhat vague and I have to admit that I'm not experienced in this topic so I would like to hear the pro's and con's.

Oliver

[Mario]

RAW files typically contain an EXIF record, sometimes a legacy IPTC record or a GPS record.
When writing back, IMatch maps XMP => EXIF / XMP => legacy IPTC / XMP => GPS and the result goes into the RAW. If EXIF / leg IPTC / GPS already exist., bla-bla. This is all documented in the help in great detail. The mapping is performed when Metadata Working group compliance is enabled and in accordance with the mapping rules set by the MWG and the ISO XMP standard and rules built into ExifTool. IMatch does not interfere with that.

This works great and for many, many years.

[lbo]

in accordance with the mapping rules set by the MWG and the ISO XMP standard and rules built into ExifTool

thanks for the information about ExifTool.

Oliver

[lbo]

re-reading the MWG guidance (4.2) I see now that "format" means the whole Exif part, not a single field. Therefore MWG seems to recommend to write ImageDescription, and that's what ExifTool's MWG:Description composite tag does. Thanks for pointing me to the source of information.

Exif "User comment" is not part of the ExifTool MWG:Description composite tag and not (doubtless) listed in MWG guidance 5.2, but I don't care whether it's written together with ImageDescription.

As currently present for XMP, a setting similar to "keep existing Exif" might be worth considering to support the "never modify a RAW file" policy. But it might be more complicated than I think so it needs thorough consideration.

This had also a performance benefit since it would prevent IMatch from re-writing a huge raw file if I change the XMP-Description. And it would reduce the amount of data written to a backup.

Oliver