Metadata and Taxonomy

You may have heard the term “metadata” thrown around quite a bit in regards to, well, pretty much anything in the digital world. Metadata is used to describe data. For instance, a book’s metadata may include the author, publisher, or copyright notice. Similarly, images have metadata to aid in searching, tracking and retrieving.

Photo metadata can be a bit convoluted and overwhelming at first glance, especially since different standards exist for storing it. Things don’t get easier when you add in different applications that read, write, and handle metadata in various ways. Still, a consistent element exists with all photo metadata, and these simple concepts can help anyone get more out of their photos.

What is metadata?
A simple and very common definition of metadata is data about data. However, I much prefer the definition from Everything is Miscellaneous: Metadata is what you know and data is what you’re looking for.

What is photo metadata?
Photo metadata is a specific type of metadata that refers to the attributes of a digital photo. It is different from other types of metadata due to its embedded nature – photo metadata is typically embedded within the image header for additional functionality and usefulness. This provides flexibility, allowing the metadata details to travel with the photo independent of the application or environment. In other words, photo metadata is interoperable.

Let’s look at an example of photo metadata in action. If a photographer uses Adobe Lightroom for post-processing his images, he can add key metadata details such as location, copyright, and keywords using Lightroom’s captioning tools. He can then send the image to a client that uses Apple Aperture. The client can open the image in Aperture, and even though the application is different, the metadata is still accessible.

Without photo metadata standards, this simply wouldn’t be possible – each application would read and write in application-specific fields, meaning that information couldn’t be exchanged between Lightroom and Apple Aperture. It’s easy to imagine how this would create headaches for everyone involved.

What are photo metadata standards?
Photo metadata standards describe consistent available metadata fields so information can cross platforms. The standards provide instructions for application developers on how to read and write information to and from the image. The most common and widely adopted metadata standards are EXIF, IPTC, and XMP.

Why are there several different standards?
In any industry, communication is easier when there is a single standard to use. Unfortunately, that hasn’t happened here, and it’s really just because that’s the way things evolved. The good news for consumers is that only application developers really have to deal with the different standards. As a user, the standards provide different types of information and benefits and most software applications handle these standards fairly seamlessly, providing the benefits of each sans the confusion. Let’s take a closer look at each of these standards:

EXIF (Exchangeable Image File Format): EXIF is metadata embedded in an image by a digital camera when the image is first captured. EXIF data includes information such as camera manufacturer, model, focal length, color space, date, and time. Most EXIF fields are write-protected and can’t be edited by software applications; this is because any editing or updating of these fields would impact the integrity of the original photo capture information. EXIF metadata is supported in JPEG and TIFF files.

IPTC (International Press Telecommunications Council): IPTC is the standard that defines information such as copyright, location, and keywords. Originally developed for news agencies in the 1990s, IPTC allows different organizations (such as news agencies) to exchange photo information by adding the metadata using photo management and capturing tools. IPTC metadata is supported in JPEG and TIFF files and has seen wide adoption by third-party software vendors.

XMP (Extensible Metadata Platform): XMP is an XML-based standard that supports a wider range of file formats (including JPEG, TIFF, PNG, GIF, PDF, AI, EPS, and DNG files). Developed by Adobe, XMP is generally easier to work with for software applications because of the extensible XML format. While XMP is viewed as a better platform by many in the industry, Adobe understood the need to work with previous standards. Because of this, Adobe integrated IPTC metadata into XMP to prevent older images from being left behind.

Despite the best intentions of Adobe to integrate IPTC into XMP, there’s still a gap in terms of compatibility. Some applications support XMP, some support legacy IPTC, and some support both. To make things more complicated, some applications may offer different levels of support for these standards (e.g. reading from both but only writing to one).

Other applications, WebDAM included, offer an all-encompassing solution by writing to both standards. This helps keep them in sync. For example, if you wanted to put metadata in your photo regarding country of origin, you could save “country=USA.” The application would simultaneously save the metadata to the legacy IPTC “country” field and the XMP “country” field for maximum flexibility regardless of application.

In terms of software, choices exist when it comes to compatibility. The popular Adobe Creative Suite (Photoshop, Illustrator, Lightroom, etc.) support EXIF, IPTC, and XMP, and even includes different types of functionality for handling images and associated metadata. Outside of Adobe’s products, hundreds of other applications, ranging from editing tools to photo database and digital asset management systems, support at least one of these standards.

Given the huge investment involved with annotating an image archive, your application of choice should include support for these widely adopted standards. The wrong choice could create a ripple effect through your digital media pipeline, forcing you to backtrack and make retroactive updates and corrections. If you’re considering software that uses proprietary standards for handling metadata, it’s best to let it be – those types of applications will only cost you valuable time and money in the end.