Very nice article. I wish that if we were discussing motion picture production we'd consider crop factors in terms of the 1.85 ratio cropped out of a vertical piece of 35mm film--ie., the "S35" crop that most people consider "full frame" when shooting movies. There are exceptions, of course, with VistaVision, and newer big sensors. Still, it seems more appropriate to me to look at, for instance, what lens you need to use on a GH4 versus what lens you'd use on an FS100 for the same shot. For many years I shot 16mm and then 2/3" chip broadcast cameras. A 25mm lens for me was reasonably close to "normal." When doing still photography with the old Nikon, a 50mm was "normal." And with the Hasselblad, the 80mm was "normal." When shooting with the FS100, I've found I use the 35mm old Nikkor as my "normal" lens, and use the same lens for the same situation on the GH4 with Speedbooster.
I don't recall anybody shooting video or film a few years ago ever comparing lens focal lengths to still camera lenses, until the DSLR revolution came along. It would be nice to revise our thinking and leave the "full frame" still camera out of the equation when talking about crop factors for movie production.