How to Know the Location of Photos Taken With a Traditional Camera? [Solved]
We don't know how Google Photos works but we know about the methodologies that Google and other web giants use to track the users. This answer presents a generic view.
Google's advanced algorithms have seen all the places. Other users might have marked the images taken from the same place and it's quite easy to find similar places. If some other friend of yours took same or similar images and marked the city there, it's hardly a tough task.
It's easy to track you. If you uploaded the images from the same city or immediately after returning, after ever logging in to any Google applications (or use your android phone back in that city), they know where have you been. So this makes probabilistic images match easier. Also, all modern cameras save the data on which the photo was taken. Things get easier now.
Google seems to respect their users privacy. You can disable the location easily. Show where your photos were taken
Another method to know the location of photos taken with a traditional camera?
Without being able to see the actual photos in question... here are two guesses.
1. You took photos of recognizable landmarks that Google can identify
2. You took photos with your phone around the same time and uploaded them to Google Photos (or you used Google+ or Google Location History).