Confuse over EXIF / XMP

[jeffayn]

I am little confuse over Exif & XMP... are they different thing ? standard ? or ... ??

[StarGeek]

There are three major standards for metadata in image files.  The EXIF standard, which is mostly information about how the image was created. It is often used as an all encompassing name for metadata, though it is only one of the standards (yes, that's one of my pet peeves). Things like ISO, shutter speed, f-stop, time stamp, etc.  This is data that is usually written to the file when the image was taken in most digital camera.

The IPTC IIM standard was created in the early 90s.  It allowed for other types of data to be added to the image, such as description (Caption-Abstract), Keywords, location names, though not GPS coordinates, which are embedded in the EXIF group.  Also a lot of stuff related to news agencies, as I believe that's where it originated.  It's common in a lot of software developed up until the creation of the XMP standard.  It technically has some limitation on the length of data embedded.  For example, Caption-Abstract is supposed to be no more than 2,000 characters.  Each Keywords entry is supposed to be up to 64 characters.  But a lot of software ignores those limits.

The Extensible Metadata Platform (XMP) is the newest standard.  It is much more flexible than the others.  It's expandable and doesn't have the character limitations of the IPTC IIM.  It includes the IPTC-Core standard as a replacement for much of the older IPTC IIM.  It can be embedded in images, video, pdfs, etc, or used as sidecar files.

You should rarely have to actually change data in the EXIF group.  Most often it will be just to add GPS data or change the time stamps if the camera was not set properly.  IPTC and XMP are what you would most commonly edit, depending upon the programs you use.  Programs like Lightroom will commonly write to both IPTC and XMP, except in the case of raw files, where it's usually just the sidecar file.