EXIF data, in my experience.
[QUOTE=FarFarAway;3400761]I looked at the pic I have on SA in the private section. It's EXIF data is just the color space and XY dimensions. That's no risk, right? I made it by taking a real camera pic through a number of different apps and formats. When I get pics from girls, I always look in the photo info, b / c if they took them (selfies w / a smart phone), sometimes there is GPS data too. What is the risk to me w / mine?[/QUOTE]By the time a pic moves through all the apps, sites, etc. , you won't see anything useful (I. E. Location) left.
Occasionally, someone will send me a pic directly from a smartphone (with "Location" set to "on" and I can see practically into her room using the map coordinates on a Google Map display. Except for phone-to-phone pic sending, I'd say there's a 0% chance of exposing anything "public. ".