Re: What is the IPTC equivalent for XMP fields?

[fincire]

Somewhat in line with this topic, I was hoping you might share more about metadata tags that EXIFtool warns are "dangerous." Are they dangerous because they're not written reliably? Or because they share data with some other tag, therefore potentially overwriting something you want to keep?

I don't mean to hijack the thread, I'm just curious -- this isn't important so didn't seem like it was worth a topic of its own.

[Mario]

Where does ExifTool mention dangerous tags, in which context?
Some tags cannot be written, some tags are considered unsafe to write, e.g. camera make and model (because many RAW processors depend on this information and may trigger the wrong process when the make/model does not match).

Sometimes ExifTool refuses to write when it detects problems in the metadata (usually caused by other software messing things up) or corrupted metadata.

XMP is always safe. IPTC too. Most EXIF tags to. Maker notes, not so much.
See also https://exiftool.org/faq.html for more info.

[fincire]

Yes, pardon me, I meant the alert indicating that a tag is unsafe to write to. The warning pops up when you try to create a metadata template that uses one of the unsafe tags.

I've seen it with various tags, often in less-common namespaces like PRISM and PMI -- both the predictable "read only" tags like camera make/model, but also some that at least sound like they'd be harmless enough and would be handy for a custom metadata view (I'd list some examples, but Imatch pretending it can't hear me right now because it wants to comb through every atom of my database for some reason. When it finishes up I'll find some and post them.   ).  I assume ExifTool has a good reason for not wanting those tags in its life, I just never knew what it was. 

 

[Mario]

I assume ExifTool has a good reason for not wanting those tags in its life, I just never knew what it was.

Yes, that it usually the case.

When ExifTool flags a tag as unsafe to write, IMatch respects that and indicates this in the UI accordingly. ExifTool is usually right.

The Metadata Panel marks tags from IPTC/EXIF/GPS which have counterparts in XMP as read-only, to prevent the user from changing these tags directly and seeing them wiped out when IMatch maps back from XMP to EXIF/IPTC/GPS during write-back. Most people don't know the complex interactions between metadata standards, and I want to prevent IMatch users shooting themselves in their foot accidentally. Metadata is a mess, even on a bright and sunny day.

In general, only change XMP metadata in IMatch (which is the default everywhere).
It is the superior standard and encloses legacy IPTC, EXIF, GPS, IPTCCore and IPTCExt. This usually covers all metadata photographers (hobby, pro and institutional) will ever need. IMatch and ExifTool take care during write-back that native EXIF/GPS/legacy IPTC data is updated from the XMP.

ExifTool currently lists about 15,000 metadata tags, from a wide range of formats. And maybe 50 XMP (?) namespaces created by various software products and organizations. There are several custom namespaces like DublinCore or PRISM useful for special audiences. IMatch supports them of course. But when ExifTool marks a tag as unsafe to write, IMatch will mark it as well. I don't know the details of why and how in most cases, but I know that Phil Harvey does.

Feel free to post questions in the ExifTool forum if you need detailed information about a specific tag or tag group or a custom XMP namespace.

[fincire]

I'd say it's probably wise to protect users from themselves when it comes to metadata. "Metadata is a mess," after all. You say so in the help file, you say so in the forums, everything I've seen backs that that up, and I don't see how anyone in their right mind could argue otherwise. In fact, calling it a mess is rather generous. Disaster, maybe. Train wreck. Imbecilic misery engine. Ruinous amalgam of nonsensical conflicts, half-baked dead ends and ill-considered false starts. 

Thanks for the explanation. I will now accept that there is no secret ideal hidden deep in the mountain of supported namespaces (except XMP, I suppose, but even that is only top dog because the competition is such a catastrophe). The real message is "stop looking for something that doesn't exist." 

[Mario]

AFAIK PRISM is rarely used, IPTCCore and IPTCExt is the clear favorite in most scenarios I know. ExifTool (and hence IMatch) support PRISM, though. There is just no pre-made Metadata Panel layout. If you want to work with PRISM, you can easily create your own Metadata Panel Layouts.