What is metadata and how is it used?

Metadata is information about an image that is stored within the image (or alongside it) and can do three differents jobs: storing EXIF shooting information embedded by the camera, IPTC data like keywords added by the user, and XMP or other ‘sidecar’ files containing editing steps.

EXIF data is embedded automatically

EXIF shooting information is embedded automatically by the camera. You can’t edit it directly without special software tools and if you don’t want it to appear in images you share with others you have to use special workarounds.

This EXIF data is really useful, especially to photographers themselves. It lists the camera and lens uses, the ISO setting, the shutter speed and aperture and more. If you use an image cataloguing program like Lightroom or Capture One, you can search and filter your photo library using this information. If you need to find photographs taken on a particular date or with a particular camera, the EXIF data will help you do it.

IPTC metadata is optional

IPTC stands for International Press Telecommunications Council, and it’s a standard system for adding information to photographs. Not all software uses it, or the full set of IPTC fields, but it is widely used. The most common use is adding keywords to images.

As a photographer you can use IPTC metadata to add information that’s useful to you or your clients. It’s not essential, but basic information like keywords, locations and copyright notices are used widely by photographers. IPTC metadata can be stored within certain image file types (JPEG, TIFF) but not RAW files, which cannot be edited or modified directly. With RAW files, image browsing or cataloguing stores IPTC metadata in ‘sidecar’ files alongside the original photo or within the image catalog database.

XMP and sidecar files

XMP stands for XMP (Extensible Metadata Platform). It’s a type of file designed to sit alongside a photo that contains important data about that photo, which may be IPTC metadata added by the photographer or image-editing steps applied by programs like Lightroom, which don’t modify image files directly but instead store your edits as separate data files. Other software publishers may handle editing metadata with their proprietry ‘sidecar’ files.

Sidecar files are, basically, metadata files stored alongside your photos. It’s important that they don’t get separated from your photos, because if that happes your additional metadata and editing steps for that photo will be lost.

Which metadata types do you actually need?

• EXIF metadata, or shooting information, is stored automatically in the image by the camera. You don’t need to do anything.
• IPTC metadata, often just keywords, is optional. You might find it useful later on, but it’s not compulsory.
• XMP and sidecar files are created automatically by your software to record keywords and other information together with any editing adjustments made in non-destructive photo editors like Lightroom. You don’t need to do anything except make sure you don’t lose them. Some programs create image catalog databases where this information is stored instead.