Configuring Metadata 2

[DigPeter]

Much has been said in recent posts about IPTC not being considered standard by the MWG.  The default setting in Metadata 2 preferences for configuring, for instance jpg files, shows Write IPTC as "Yes".  I have no need for IPTC in IM5 - I am not a professional photographer whose clients might insist on IPTC data.  What would be the implications of disabling this? 

[Mario]

IMatch by default updates existing legacy IPTC, but does not create it.

[Ferdinand]

I don't think that there any any implications, until you want to use software or a web site or photo agency that expects IPTC.

Of course if your existing images have IPTC and you disable this then you might get an inconsistency between XMP and IPTC when you edit XMP, but that's only a problem in practice if the first sentence applies.

[DigPeter]

Thank you Mario & Ferdinand.
I do not deliberately add  IPTC data to my new images, but there are those  images brought over from IM3 which do have this.  The new images, added since transfer to IM5, also show IPTC:Application Records\Keywords being written when Write IPTC is configured "Yes".   Would it be correct that IPTC is added by Lightroom during conversion/editing?

[DigPeter]

Further to this, I have just deleted all IPTC data in a jpg file through exif tool.  Back in IM5, with Write IPTC is configured "Yes", I changed a KW in that file and all IPTC has been restored.  It seems that by default IPTC is created, not only updated.

[Mario]

Which IMatch version are you using?
What are your Metadata 2 settings?
Logfile?
Did you check that the file really has no IPTC data in the ECP?
Did you rescan the file after updating it with ExifTool?
When IMatch writes data, it tests for certain IPTC tags, and if they are found and IPTC write is enabled, it will write data, else not, unless create IPTC is enabled for the format.

[DigPeter]

Mario - I am not reporting a bug at this instant, just trying to seek understanding.  I have just downloaded a jpg file direct from camera and see that it has no IPTC data.  When assigning keywords and writing back, IPTC fields are not included.   I will look further into this before decidin whether to make a bug report.

[Mario]

I assume you are using 5.2.6 (current versions).

When IMatch writes back metadata (or propagates keywords internally), it does this:

1. Is IPTC write enabled for the format?
2. If Yes, check if the file has legacy IPTC tags.
3. If there are IPTC tags, write back.
4. If there are no IPTC tags, check if "create IPTC" is set.
5. If yes, write IPTC.

[DigPeter]

Thank you Mario for this explanation - I now understand the function more clearly.

Having tested it again, I am happy that there is not a bug.

[joel23]

Much has been said in recent posts about IPTC not being considered standard by the MWG. 

Well, it is often spread (kolportiert) like this, but... it's not that easy. I am not able to find one negative word about IPTC in the MWG compliance guide.
MWG says:

2.4 Relationship to standards organizations
There are a number of established standards, such as Exif and IPTC, which are widely used by the digital photography industry. This effort is not intended to replace existing industry standards, but rather to build on them by providing resources to improve interoperability and metadata preservation between them. This is based on significant understanding of the industry (customers, scenarios, technologies) and experience in building the products that capture, process, store, share and transmit digital photographs.

4.2.3.2 Handling IPTC-IIM and XMP
This chapter discusses reconciliation guidance between IPTC-IIM and XMP:

Reading IPTC-IIM and XMP
The use of IPTC-IIM is significant in professional workflows, and is also present in some consumer oriented tools. Although this document only directly addresses a few IPTC-IIM fields, there are several dozen in professional use. The IPTC-IIM values have length limitations and often character encoding issues that can make a conversion from XMP to IPTC-IIM be lossy.

Writing IPTC-IIM and XMP
Changer

• XMP and IPTC-IIM SHOULD be consumed according the reconciliation guidance described above.
• If IPTC-IIM is already in the file, a Changer SHOULD write data back to the file in both XMP and IPTC-IIM ¡V otherwise only XMP SHOULD be written.
• IPTC-IIM SHOULD be written using the Coded Character Set (1:90) as UTF-8 (see ¡§Section 1.6 Coded Character Set¡¨ in the IIM specification).
• If the IPTC-IIM has not been written in UTF-8 before, a robust Changer SHOULD convert all properties to UTF-8 and write the corresponding identifier for UTF-8 to the 1:90 DataSet.
• If IPTC-IIM and XMP are both present, whether changed or not, a Changer MUST create or update the checksum value as described earlier.
• If no existing metadata is in the file, the Creator guidance SHOULD be followed

note: there are three actors definitions in MWG: Consumer (websites like Flickr, reading metadata only), Creator and Changer (PS, Exiftool, LR, IMatch, Geosetter, etc. pp.)

Not only Photoshop creates IPTC for DNG, PSD, TIF, JPG and maybe for other file formats per default. Geosetter does as well for DNG, JPG and TIF.  Here MWG tells that a creator (e.g. PS) should not create IPTC-IIM unless backward compatibility with non-compliant Consumers that don't read XMP is a requirement – otherwise SHOULD write XMP

In this context mentioned applications strictly seen are not MWG compliant (there is IMHO worse than that), but I guess they just made things easy for themselves: whether an IPTC record exist or not, create or write it. So they don't have to care about if a reconciliation has to be done or not: they just write everything in order to keep them synced.

[DigPeter]

I am sure that Mario has chapter and verse on this, if he has time.

(kolportiert)

I think a better translation might be "peddled", a slightly derogatory term = widely or persistently promoted an idea - as in propaganda.  ("to peddle" also means to trying sell small items by travelling around the country.)