Metadata is a term used to describe structured information that describes, explains, locates or makes it easier to retrieve, use or manage an information resource. In digital photography it is the term used to refer to the data which can be embedded into the photograph to allow the user to be able to search for, retrieve or identify who the photograph belongs to. In the case of a photographic image it is the set of standard information about a file and includes such information as photographer name, resolution, colour space, copyright details, keywords and lots more. When we include it within our images it allows us to streamline our workflow and organise the images on specific keywords, but also allows the digital identification and supports the archiving and preservation of the image. You may also come across it being referred to as IPTC metadata, IPTC information or Exif metadata.
There are 3 forms of metadata in a digital photograph, that which is added by the manufacturer and hidden, that which is added by the manufacturer which we can see but not manipulate, such information as the date and time and the camera settings for example, lens, focal length, aperture, shutter timing, white balance etc. While the third element is that information that we can add, such as keywords.
It has a number of functions, but the two primary ones are the ability for us to catalogue our images by allowing them to be found by relevant criteria, identifying resources, distinguishing between similar images and giving location information. The other use is for us to embed captions, keywords, copyright information and other facts into our images so that others who have the ability to read it can identify that it is one of our images. If images contain relevant metadata it allows them to also be searchable on picture library websites, or other websites.
The most common form for embeding metadata into a file is using an XML header. This can be included in any of the photo file types, jpg, tif, RAW and so on, and when doing so increases the file size slightly. Embedding information in this way is a good idea, it means that the information will travel with the file itself, whether over the internet, emailed, written on a CD-ROM or external hard drive.
When looking at an image with software that allows you to view/edit it the set of metadata that you can add and edit for a file is referred to as IPTC. IPTC was a standard created in the late 1980's but today it has moved on and been replaced by other formats, however the new formats are usually based on the original IPTC and when you look at this information in a software package such as CaptureNX2 or Photoshop IPTC will still head the column of data it refers to. Adobe created it's own format called XMP back in 2001 which ostensibly meant that more information could be stored, however if you open a file in Photoshop with IPTC information it will save it with this original and its XMP data simultaneously.
When you compare metadata across different cameras, photograph types ie Jpg, Tiff, RAW, or different software packages there will be differences on what can be seen and added as well as differences in where it is stored. For example Nikon CaptureNX, View and Transfer add data to the file whereas Photoshop also adds some of the details to another file (XMP). You will also find that when adding the IPTC metadata in one package it may not display in the same position or even display at all within another system.
Adding User definable Metadata (IPTC)
Adding metadata to a photo can be done in a number of ways. If you are a Nikon user and use Nikon Transfer to upload your images to your computer you can add some metadata in this process, by setting up preset metadata files that can be added on upload. Or you can add it via a photo/editing system such as Capture NX or Photoshop in two different ways by adding to each file individually (time consuming, but would give more accurate data per file), or you could set up preset metadata templates which can be added to a number of selected files at once. If you are using the later option it is probably better to set up the template for the general information such as copyright, photographer details etc and then add picture relevant keywords and captions individually. We have another article looking at Keywords and Captions - click here to see it.
Finding the Metadata using Software
Within the various software/editing packages that work with photographs the metadata is filed in different locations although usually within the file information section. Here we are going to take a look at where you can access and add to the metadata information with Photoshop and Nikon Software.
In Photoshop CS3 using Adobe Bridge to view the images on a directory, highlight a photo and in the right hand panel you will see the list of Metadata information for that image, you can also add the IPTC metadata here. When you then open the image in CS3 itself you need to look under the File menu and take the option 'File Info' this then lists the following headings - each one of these have a number of elements within them, those highlighted with an * are not able to be modified by us:
Within Adobe Bridge you can also set up metadata templates to populate files with standard information such as photographer, copyright details and so on, and as well as applying this to an individual image you can select a number of images and apply the template to the group.
Within Nikon Transfer you can set up the preset information under the 'Embedded' tab and the information that it allows you to add is more generalised details which might be relevant to all the images being uploaded in that batch such as who took the photo, location etc. In Nikon View when an image is selected the 'metadata' browser in the left panel displays the camera details and the IPTC data you can add to. Within Capture NX2 you will find it under the Edit menu under preferences - 'XMP/IPTC presets'. What you will see and modify will vary between them and to try to show you the type of information that can be included within the metadata and to illustrate what can be seen/added (using a Y) across Photoshop and the Nikon software packages the following table lists the IPTC titles when looking at a Nikon RAW image.
We have a separate article looking at Geotagging a way of getting the GPS data into the metadata fields.
It is wise to begin adding metadata with a structured approach, and being consistent and using templates will make your life easier.