Metadata
Three acronyms, three roles
EXIF, IPTC, XMP: three names for different things we often treat as interchangeable. Understanding who keeps what prevents a lot of loss during an export or a migration. In one sentence: EXIF describes the capture, IPTC describes the content and rights, and XMP is the modern container that can carry both.
EXIF: the technical data
EXIF (Exchangeable Image File Format) is written by the camera at the moment of capture. It holds the technical data: date and time, camera and lens model, aperture, shutter speed, ISO, focal length, sometimes GPS coordinates. These are facts of capture, valuable for finding and sorting, generally not edited, but essential to preserve.
IPTC: description and rights
IPTC (a press standard, today “IPTC Core/Extension”) carries the documentary and legal information: title, caption, keywords, creator name, copyright notice, usage terms, location, people. This is the layer you fill in, the one that makes an image understandable and usable, and the one that protects your rights.
XMP: the container and the sidecar
XMP (Extensible Metadata Platform, an Adobe standard) isn’t a third competing list of fields: it’s a container format in XML, able to carry IPTC fields, part of the EXIF, and software-specific data (ratings, edits). Above all, XMP can live two ways: embedded in the file, or in a companion file, the .xmp sidecar placed next to the original.
Embedded or sidecar?
- Embedded: the metadata travels inside the file itself. Convenient, but it means rewriting the file, a problem for a proprietary RAW you want to keep untouched.
- Sidecar: a separate
.xmpfile accompanies the original, which is never modified. This is the non-destructive approach: you enrich the documentation without touching a single byte of the capture.
What gets lost in a migration
Losses almost always happen at the border crossings: an export that doesn’t embed IPTC, software that ignores sidecars, a conversion that overwrites the existing XMP instead of merging it. The classic symptom: keywords and captions painstakingly entered, gone after a change of tool.
Recommended minimum fields
For an image to stay usable, fill in at least: title, creator/author, copyright notice, description/caption, keywords, date, and location. Seven fields that separate a documented image from an orphan file.
In practice
- Preserve the original EXIF: don’t rewrite it without reason.
- Fill in the IPTC: that’s where documentary and legal value lives.
- Prefer the XMP sidecar to enrich without modifying originals.
- On migrations, confirm the XMP is merged, not overwritten.
Obscura Flow reads all three families (via ImageIO, and ExifTool when present) and writes enrichments to an XMP sidecar, never modifying your originals, merging rather than overwriting metadata that’s already there.