This is really useful information. The fact that you're seeing that name in the exif viewer confirms what you're saying, that the camera is actually naming them this way. That leads me to believe that my years-old import system for all photos has been responsible for naming them with the time and date. I never knew that.
I thought that there were several ways in which I'd always been importing photos, and that all of them basically resulted in this same naming. But now that I think more closely about it I think that Dropbox has just handled all the imports for years, and that it's Dropbox that's been saving me with the useful naming convention.
So now I'm kinda stuck. I was going to give Photos a try as a simple inbox, to then be able to distribute the photos to wherever they eventually need to go, or be stored. But this ruins my workflow because they're all named this useless IMG#.
I definitely don't want my photos touched by Photos now. I'd always heard it was intrusive and made them useless and locked in to a piece of software you couldn't ever really recover from, I'd just hoped that had changed. But right off the bat it's already rendered my first import of photos useless. I'm just glad I haven't deleted anything. I can let Dropbox import them and save me.
It just seems a useless naming convention. I'm amazed more people haven't had this problem.
