https://www.imore.com/google-photos-may-be-free-what-personal-cost
“The potential of photographic data
An image may be worth 1000 words, but image metadata may spill far more information than that, especially when applied to a Google service. According to this year’s Google I/O keynote, the Photos service will offer a search function that can find people, places, and objects — all without any active tagging on the end user’s part.
It does this in part by scanning your image’s metadata: the location and other information your camera builds into the underlying code of your digital image. For the rest, I suspect Google is inventing its own supplemental metadata, using rapid image scans and automatic face detection as part of the company’s continuous “machine learning” system. It may not be perfect at the start, but as Google gets more and more photographs to scan, it could become the most accurate auto-tagging service on the Internet.
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Where's Nessie ? This is just a photo added to make the post a little more enticing.