Comparison of photo metadata and tags in other applications

This page describes how Shotwell and other photo programs import and export information through EXIF/IPTC/XMP tags. The metdata "paths" are Exiv2 tags.

1. Tags

Tags may contain the following information:

single-line photo caption ("title')
multi-line photo description ("notes" or "comments")
keywords ("tags" in some programs including Shotwell)
rating

1.1. EXIF

There are three tags in the standard EXIF specification that may carry relevant information.

Exif.Image.ImageDescription (described in the spec as "image title")
Exif.Photo.UserComment ("content description note")
Exif.Photo.MakerNote ("manufacturer notes")

Also in the standard specification are a few Windows-specific tags:

Exif.Image.Rating
Exif.Image.XPTitle
Exif.Image.XPComment
Exif.Image.XPKeywords
Exif.Image.XPSubject

1.2. IPTC

photo caption

Iptc.Application2.Caption
Iptc.Application2.Headline

keywords

Iptc.Application2.Keywords
Iptc.Application2.Subject
Iptc.Application2.Category
Iptc.Application2.SuppCategory

rating

Iptc.Application2.Urgency

1.3. XMP

photo caption

Xmp.dc.title
Xmp.photoshop.Headline

photo description

Xmp.dc.description

keywords

Xmp.dc.subject
Xmp.lr.hierarchicalSubject
Xmp.digiKam.TagsList
Xmp.photoshop.SupplementalCategories

rating

Xmp.xmp.rating

2. Photo Programs

2.1. Program Notes

F-Spot only really cares about keywords. It has a comment field which doesn't seem to be used for much. In addition to the regular tag metadata, it can use location XMP info to create "places" tags. See below for more details.

digiKam only uses descriptions. Multi-line or long descriptions are cut short with an ellipses in certain places, acting as captions. It can, however, modify metadata that it doesn't use in the application; this is done with specific metadata editing tools.

Picasa and WLPG (Windows Live Photo Gallery) can import keywords from multiple tags, but digiKam only grabs keywords from one set at a time.

The WLPG properties dialog lets you read and edit the "Comment" and "Subject" fields, which get written into Exif.Image.XPComment and Exif.Image.XPSubject, respectively.

On export, iPhoto strips all Xmp tags and writes relevant information into the respective IPTC tags.

Aperture offers immense fine-grain control over metadata.

2.2. F-Spot Imported Tags

F-Spot looks at the following tags during import, and imports according to below:

2.2.1. Title/Comment

But only uses http://ns.adobe.com/exif/1.0/UserComment

2.2.2. Rating

First uses Urgency, but if Rating exists uses Rating.

Adds them as Tags to the photo. Internally F-Spot stores the IPTC tags (City, Country, Location, State) under corresponding virtual tags (only in f-spot db, not in embedded tags)

2.2.4. Subject / People

Adds them as Tags to the photo, no hierarchy is saved.