"What is the elusive gleam reflecting off so many surfaces in so many ads really selling?"If you’ve purchased a new phone or TV in the past few years, you may have noticed that night-time viewing has caused your eyes a bit more strain. That’s because many new displays are equipped to produce, in one flavor or another, a “high dynamic range” image — HDR, for short. A fundamentally relative and fuzzy term, HDR purports to produce brighter whites and inkier blacks than have previous display technologies. The recent iPhone 12 family, for instance, touts a peak brightness of 1,200 nits.