The following is a Plus Edition article written by and copyright by Dick Eastman.
Congratulations if you have scanned your old family photos and documents or invested in a digital camera to preserve today’s pictures for future family historians. Before resting on your laurels, take a moment to recall all the old photos you’ve come across that you wish had labels describing the people, places, or events pictured. Your digital images have a built-in capability to create such labels – descriptions that won’t get separated from their subjects – with ease that would amaze our forebears. With today’s image files, what you see is only part of what you get! Let’s take a look “behind the scenes” of your digital photos.
All sorts of information can be stored inside the digital file itself, such as:
- Date and time information. Many digital cameras will print this on the picture, but they also can save it with the image file.
- Camera settings. This includes static information such as the camera model and make, and information that varies with each image such as orientation, aperture, shutter speed, focal length, metering mode, and ISO speed information.
- A thumbnail for previewing the picture on the camera’s LCD screen, in file managers, and in photo manipulation software.
- Descriptions and copyright information.
- Longitude and latitude where the picture was taken
- Any information about the picture or its subject that you choose to add, using one of the free or cheap photo editing packages I’ll describe in a bit.
This extra information is called metadata. Simply put, metadata is “data about data;” that is, it describes the context, content, and structure of a file.
In the case of image files, the metadata uses a special set of rules called Exchangeable Image File Format, or EXIF, to describe how large the picture is, the color depth, the image resolution, when the image was created, and other data. You normally cannot see this information when looking at the image or when printing it on a photo printer.
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