June 6, 2018
Metadata for dummies
For those who have never heard about it and those who thought they knew everything : what are the metadata, what are they for and who are they serving, how to fill them well ...
Metadata, what is it ?
The general term metadata refers to "appendix" data in relation to the main data.
When dealing with images, the main data is the set of pixels that constitute it, the additional data are those that will accompany these pixels in the same file to provide various information described below, including those on the author and his rights.
Credit metadata in particular will allow the person who finds a photo to know who it belongs to. Yes, they have the same role as the labels stitched by your mom on your business!
Often confused with HTML (meta, alt, caption, figure …)
Image metadata is often confused with :
- The metadata of the HTML page : this is information used by the search engines to refer pages, their format follows the HTML standard (<meta> tags), it usually provides the title, description and key words that summarize the text content of the page, to make it easier for robots (or "crawlers") to index the web.
- The text ("legend", "notice", "tooltip") that accompanies an image in a publication : in the web page containing the image, HTML code elements such as ALT, CAPTION, FIGURE, FIGCAPTION and others may used to make certain information readable by crawlers and readers. We can find credit information or copyright in these HTML fields, without them being present in the image file itself.
It is on this confusion that the alibi of many online publishers often rests (see our article on the state of image metadata in 2018) : to publish in HTML the information of credit / copyright does not justify the fact of erasing the metadata of the image file itself, because the HTML code is that of the page and not of the image.
What are the different types of metadata ?
For images, there are 3 types of metadata, corresponding to standards defined at different times and for different uses.
EXIF (Exchangeable image file format)
EXIF is a mainly technical information about a snapshot (camera settings : aperture, shutter speed). Most of them are filled automatically by the device :
- Brand and model
- Date of the shot
- Shutter speed
- Opening of the diaphragm
- Sensitivity (ISO)
- Focal distance
- Flash enabled or disabled
- Light source
- GPS coordinates
IPTC (International Press Telecommunications Council)
IPTC is an information about the author of an image and the subject of the photo (coordinates, keywords ...). They are usually filled manually by the photographer and supplemented by the agencies. Today, this IPTC data is part of the XMP system.
- Name of the author
- Phone number
- E-mail adress
- Country where the photo was taken
XMP (Extensible Metadata Platform)
This is the most recent metadata standard. This format allows you to store a wide variety of information because it is based on XML, so extensible.
It includes all EXIF and IPTC information and adds many more. It also allows to fill in some fields in several languages (title, description, license ...).
"Must have" metadata for photographers and agencies
Why fill them ?
When your photo is published on the internet: everyone can take it.
The photo (say a JPG, but it is true for PNG, TIFF ...) is published and visible via a web browser : it can be downloaded and republished elsewhere, out of its original context. How ? Right-click-save-under, view the source code of the page, and other tips found everywhere in three clicks.
The usefulness of metadata is to embed information in the same file as your pixels. If the JPG file is published in a new page that does not mention the source (or the author, the description of the photo, its rights), its metadata, they always contain the info. In theory ... (see our investigation on the disappearance of metadata on the web).
Who reads metadata and how ?
The "honest people" - do not laugh - the iconographers, the professionals who want to know who to credit, the journalists who want to be sure of their source.
To read metadata, you can either open the image under image editing software, or use plugins on most browsers. In any case it takes a little effort, the iconography work is sometimes close to the police investigation!
When the metadata are missing, it remains as a last resort to do a reverse search on an image search engine. On Google Image or Tineye, it is without guarantee of result because they will only refer you to the page where these images were found. Unless the IPTC field "author" is still alive, in this case Google Image will mention it.
Which IPTC or EXIF fields are really useful ?
You are a photographer or an agency : your credit and your copyright must be part of the picture. It is therefore these metadata fields that you must fill in priority.
You photograph a subject: the date, the place, the description, the people photographed, all this is part of the photo. These metadata fields are important, if they were systematically filled and preserved, there would be more fake news !
In short, metadata is useful, some more than others :
- your details,
- your website,
How to fill this fields ?
With publishers in the market, Lightroom is the best known but many editing software or composition allow it, more or less intuitive.
The problem is that the moment you publish on Lightroom and the moment when you publish your photo are sometimes very distant.
Thus, it is before distributing a photo (sending by mail to the editor, a weTransfer to your agent, a post on the social networks, a push on your web site ...) that one realizes that one did not put all the keywords we wanted, that we are not sure of having put our address correctly, that the title is in the right language, etc.
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