What is IRE? What does it have to do with today's technology?

The term IRE is frequently used in video measurement of luminance. But just what does it mean? Is it different from percentage? I examine the meaning of the acronym and the origins of the term. And I ask why a term defined more than 50 years ago for an obsolete technology is being used today. I also take a look at video levels, a confusing term as level ranges for video can be either video levels or full levels, data levels or legal levels. Not to mention Full range and SDI full range. And what are colour bars? And EBU?
Links
Proceedings of the IRE
www.worldradio...
EBU R.103
tech.ebu.ch/pu...
Attribution:
IRE logo
Smithsonian Libraries and Archives, CC0, via Wikimedia Commons
href="commons.wikime..." Institute of Radio Engineers, Public domain, via Wikimedia Commons