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What type of metadata should I add to my photos? IPTC, XMP, or EXIF? I want to add copyright info to my photos.

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3  
Is this strictly from the point of view of getting a copyright notice in the metadata somehow? Is there a special need of some sort that would lead you to one over another? –  mattdm May 17 '11 at 20:13
    
I want to put my name and email address in the metadata of my photos. This is primarily for copyright reasons, since the photos will be on my blog. That is all. –  JoeHobbit May 18 '11 at 1:54
    
I'm assuming JPEG files? –  mattdm May 18 '11 at 2:49

5 Answers 5

Good question: Copyright, Description, Creator and Date/Time are the only fields that are present in all three metadata formats (Exif, IPTC-IIM & XMP).

Generally, when to use which

Metadata Working Group's recommendation is to use


General answer on metadata reconciliation

I.e. if two or more are present, which wins?

If both (native) Exif and XMP are present, the aforementioned four fields are the only fields that get mapped between Exif and XMP:

 Exif  ∧ ¬XMP  ⇒ read Exif
¬Exif  ∧  XMP  ⇒ read XMP
 Exif  ∧  XMP  ⇒ read both, but prefer Exif

IPTC-IIM and XMP can have a lot of more data in common. Good things to note are:

  • IPTC encourages the use of IPTC Core, which can be written to both IPTC-IIM blocks and XMP blocks; and use the (older) IIM data just in the IPTC-IIM block.
    • Moreover: it is recommended to write the IPTC Core data to XMP, unless backward compatibility is needed.
  • IPTC-IIM has length limitations, while XMP hasn't.
  • to help solve possible conflicts, a checksum of the IPTC-IIM data should be written.

So, if both IPTC-IIM and XMP data are present:

¬IPTC-IIM  ∧  XMP                     ⇒ read XMP
 IPTC-IIM  ∧ ¬XMP                     ⇒ read IPTC-IIM
 IPTC-IIM  ∧  XMP ∧  (Checksum match) ⇒ read both, prefer XMP
 IPTC-IIM  ∧  XMP ∧ ¬(Checksum match) ⇒ read IPTC-IIM
 IPTC-IIM  ∧  XMP ∧  ¬Checksum        ⇒ read both, prefer XMP

Above suggests that Exif and XMP are the most preferred. In my opinion, Exif is great for technical details of the photo (time, aperture, focal length, white balance, GPS etc.) and XMP is great for the rest (keywording, post-processing, rating, description etc.). While the Exif data could be written to XMP, I wouldn't trash the Exif as it is so much more widely used and supported than XMP.


Concerning Copyright metadata

Remember, only Copyright, Description, Creator and Date/Time exist in all three metadata formats and the reconciliation guidance is specific for each property — Date/Time being the least straightforward.

Exif Copyright (33432, 0x8298), IPTC CopyrightNotice (IIM 2:116, 0x0274) and XMP dc:rights are (should be) mapped together. The mapping happens in the program that reads the data, so it cannot be 100% guaranteed. However, CopyrightURL should be stored in XMP xmpRights:WebStatement.

So the ultimate answer is: whatever fits best to your workflow. How do you plan to use the info? The copyright info is, well, just info and as @Roland said you might need to mention the copyright explicitly, which metadata generally isn't. If in doubt, write the info to all three.

I usually write the copyright info in to the IPTC Core, which Lightroom most probably (being an Adobe product and Adobe being a member of the Metadata Working Group) ultimately writes into XMP.

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IPTC core defines a few pieces of meta data information that, I think, is appropriate to your purpose:

  1. Copyright notice
  2. Creator
  3. Creator's contact info (including email)

And a whole lot more. Read the spec, I think you'll see that it covers your needs more than adequately and there are plenty of tools (Adobe's various options, like Lightroom or Bridge, or exiftool) that can do this in batch.

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Depending on where you live, you may need to mention copyright explicitly, this depends on the laws of your country obviously.

I personally add a simple copyright statement in camera with EXIF and IPTC later when I import to digikam.

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I generally set the comment-field to something like Copyright 20XX / Creative Commons CC-BY / Morten Siebuhr / my@email.tld on JPEGs I hand out. I (mis)use the comment-field, as it is the one even fairly ignorant users will have a chance of being exposed to.

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All rights to this photograph belong to ...

It doesn't have to be complicated.

I personally use EXIF

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