Worth Eleven-Hundred Words: Digital Pictures Capture More Than the Moment
Remember in the 'olden days' on the back of many of the photos that were shoved into a photo album there was some handwriting? Usually the writing described when the picture was taken, where and what it was a picture of.
January 12th, 1980
Toronto CNE Fair Grounds
Mom and Dad in the bumper cars
Ok so handwriting wasn't always perfect and lots of photos didn't have anything on the back, but those that did - they had context for us and made the image special.
With digital photos, we don't have a 'backside' to write that helpful information. But photographers and camera makers have lots of things they want to write down. When they took the photograph. What model of camera. What kind of lens. What camera settings they used. All this is separate from the data about the photo itself - we call this "metadata".
Now there are many ways to keep track of metadata. When you put a photo (and any file) onto a computer, the operating system - like Linux, Windows, or Apple's Mac OS - keeps its own metadata about the file. This is called filesystem metadata. It's just like the margins of a photo album. Every time you put in a photo, you write some notes in the margin. "Top right photo. May 15th, 1989, Dad took a picture of me at the CNE".
But when you give a copy of the photo to someone else, you don't give them the album itself. Even if you show it to them, they might not write down the notes in the margin, or they might forget. When you move the photos to a different album, all the notes are left behind. Ten years later, nobody remembers why there's a photo of ducklings mixed in with your wedding photos.
Sometimes, there's some information that we really don't want to lose. Storing metadata outside the file is unreliable, as we've seen. So a group of Japanese camera makers got together and came up with the Exchangeable Image File Format- or Exif - which stores this information inside the picture file itself. Just like notes on the back of a photo, Exif metadata travels along with the digital photo file. If you paste a copy of the photo onto a thumbdrive or e-mail it to a friend, all the notes travel with the copy.
Who puts Exif data into pictures? Nowadays, almost every camera does - including your smartphone's camera. Unless you're developing your own film in darkrooms, chances are your camera is storing Exif data in the pictures it takes.
More than just cameras - photo editing or viewing software also writes Exif data into pictures. When you edit an image, Adobe Photoshop will save a little Exif tag called "Software", and put into it the version of Photoshop and whether you're on Windows or Mac.
What kind of data is stored in Exif data? There's the usual suspects, such as the date and time of the photo, the make and model of the camera, and what camera settings were used to take the photo.
Then there's information that you might not know your cameras are keeping about you. Your GPS location. How many pictures you've taken in the lifetime of this camera. What version of firmware your camera is running.
But wait, there's more! Depending on the camera, you can find very interesting nuggets of information. When the camera was last powered on. Acceleration - how the camera was moving. The serial number of the lens. What direction the camera was facing. How far away was the subject. And as mentioned above - sometimes it's possible to tell what software was used to edit or view a photo.
It's easy to see why this is a treasure trove. A great many things can be inferred from Exif data. Did your client take this photo? We can generally determine what camera or phone took the photo. If there is GPS data, we can determine when and where the photo was taken. Using Exif data, in one case I was able to determine that a photograph was taken using the BlackBerry Messenger app on an Android phone specifically - not downloaded from the Internet, nor taken using the usual Camera app.
That said, there are several important caveats to using Exif data. For one, even though it's a standard, manufacturers have a lot of leeway in implementing it. Not every camera writes the same information in the same way. For example, Nikon and Panasonic cameras will write the shutter count - how many photos the camera has taken - differently.
And the specification has changed over the years, and continues to change - the last revision being in 2016. Older versions of Exif before 2016 don't even have a field for the time zone!
Collecting and interpreting Exif data may seem straightforward - but just like Grandpa's squiggly cursive handwriting, sometimes you need an expert to tell you what the notes on the back mean.
We're the experts - call us.
We look forward to assisting you