...I just wonder how common these files are?
I've never encountered such a file "in the wild," but I've seen them in one particular spot. One of the primary school teachers (from one of the Belgian or Dutch schools - I don't recall which) often posted online albums with "flipped" images. It was easy to tell because the kids often wear shirts or hoodies with text on them, and the text was reversed:
NIKE
I was puzzled by it - I don't know how I could persuade my DSLR or my phone to produce such images!
I haven't seen it in the last year or more, however, so whatever that teacher was doing, he or she has fixed it.
