Best Practices and Tools to Create Archival Image Metadata
Written By: Elena Toffalori
Metadata are an essential part of our digital world
That information-about-data layer that allows us to search, sort, share, attribute, represent, and track the provenance of our files; that's metadata. This is particularly important when approaching digital files and media with a concern for their long-term sustainability, in that metadata can be transported with the archived files, work as a finding aid, and help keep our collections relevant and usable. Accurate categorization, tagging and description of files and collections through metadata can ensure they are efficiently retrieved and contextualized by humans and software alike. Here we present some tools and best practices to add good quality metadata to archival photograph collections.
1. What's in metadata?
Working in digital media management, its preservation and presentation, we find ourselves working with metadata on many different layers – from the basics of file naming convention (a fundamental step in any media management workflow) to following specific standards for technical and descriptive metadata, and even fully custom metadata structures.
Metadata standards, in particular, can be format- or discipline-specific. When talking about digital photography, for example, two standards that are worth knowing about are:
- EXIF (Exchangeable Image File Format), which covers technical metadata inserted into digital image files by the camera; EXIF metadata fields cover technical aspects such as image size and compression, information about image capture such as camera make and model, time of creation, exposure, focal length, aperture and geolocation (if supported by the camera). Newer camera models can insert basic descriptive fields such as author and description;
- IPTC Core and Extension Standard (released by the International Press Telecommunications Council) define user supplied properties around locations, people, dates, names and subjects related to the image, its content and its creation, either from controlled vocabularies or through free text format fields; IPTC information is a standard de facto for new media and photo stock agencies, and by extension for the digital photography community; technically stored in XMP, a widely adopted metadata format;
2. Internal vs. external metadata
Data and information are entered into the image file either by users, or by automated capture from cameras or scanners. Metadata can be stored either internally (embedded in the same file as the main image data) or externally, in a separate file from the data (sometimes called a sidecar file) or even a metadata database. Digital image files inherently support both, so the result will depend on the workflow and the format chosen for both image and metadata.
EXIF data, for example, is embedded into the image at the time of capture, creation or processing, but can be extracted and displayed or stored alongside the main file by an application. The most common formats for digital images, like JPEG, DNG or TIFF (read more about that on a recent blog post) support embedded metadata in EXIF and XMP (that can be encoded as IPTC) metadata.
Some proprietary camera RAW image formats will save metadata as external text file when the image format doesn’t support embedded XMP metadata. Regardless of the information embedded in a file, additional metadata about single files or a collection can always be manually attached in a separate file (a pdf, csv, txt, a database…) if the workflow requires it – and to facilitate visualization and indexing, preferably following a standard format.
Metadata can also be erased from digital image files – either by the user on purpose or automatically by software. This actually happens with most of the image’s relevant metadata (including its filename) whenever the image is imported to most web services and social networks.
3. How to access and edit metadata
While often the creation of metadata happens automatically behind the scenes on our computer and on web servers we interact with, there are plenty of tools that make it possible to view these data – or write descriptive information into our digital files.
Besides commonly accessed metadata fields like filename, for most digital formats such as text documents and media it is possible for the creator to edit additional metadata fields, like tags and author, typically while saving the file or viewing its Info / Properties. When working with digital photographs, here are some ways that you can access the metadata layer on your pictures:
- Camera: Most digital cameras will let you view EXIF metadata on your display; the same is true for mobile devices with a camera;
- Camera applications: additional features on your camera – or mobile applications on your device, may allow you to view or edit easily metadata, for example adding a title or caption to an image, or set a photographer name to be automatically embedded within the files; (as these change quickly, try searching for “EXIF” “IPTC” or “Metadata” in your reference app store);
- Computer operating system: typically you will be able to see EXIF and any IPTC metadata embedded in a digital image by viewing its Info or Properties (depending on your operating system);
- Photo editing and viewing software: any photo editing software, from the default one available on your computer, to free software such as Google Photos, to professional tools such as Adobe Lightroom Photoshop or Lightroom, will let you view and edit image metadata.
- Dedicated online services such as Jeffrey’s Image Metadata Viewer
- Online sharing platforms like Flickr will extract and display your metadata, map your pictures based on geolocation when available, and let you change metadata or the published version of your photos and albums/collections;
- Internet Browsers: Most browsers have plug-ins or extensions which will let you view EXIF information from an online image file just by right-clicking on it;
- Always set the time and date correctly on your camera – what may seem like a harmless inattention could end up bringing chaos in your archive later;
- Mind privacy issues related to geolocation; automatic embed of geo-location data is a powerful tool, but if you’re planning to share photographs from sensitive locations – such as your own home, be aware of this and either turn off geo-location services or strip this metadata before sharing the file;
- Define a relevant filename convention; an informative filename can go a long way in providing context for your photos;
- Follow standards as closely as possible, and adopt controlled vocabularies that are discipline-specific, to help maintain consistency in your archive; in the cultural heritage area, check out for example the Getty Vocabularies);
- Start small, but organized; an organized filename and a short caption about the project or collection that the photograph belongs to, together with information about the photographer, is better than nothing (or waiting years so you can add a detailed description to each file) and will add a great value to your collection; with an editor, this kind of information can easily be batch-added to your pictures as you first import them into your computer or archive;
- Use a non-destructive editing tool to manage your photo catalog; such as Adobe Lightroom; a specialized photo catalog tool will help you batch edit your metadata and handle versions of your files, so you can export files that are optimized for the web, stripped of sensitive metadata or have watermarked copyright – all without compromising your originals;
Read more about the advantages and difficulties of working with photo metadata: