The original HDR10 standard is already old news, as Samsung and Amazon is introducing a "plus" version that flaunts "dynamic tone mapping." My reading of it is that brightness and contrast levels will now change based on the content of a scene: think of the "dynamic" picture mode on most displays, but now built into the stream or movie. This is actually the fifth major HDR standard—which is funny, since most people still have no clue what high-dynamic range even means.
HDR10+ elevates the HDR10 open standard with the addition of Dynamic Tone Mapping. The current HDR10 standard utilizes static metadata that does not change during playback despite scene specific brightness levels. As a result, image quality may not be optimal in some scenes. For example, when a movie’s overall color scheme is very bright but has a few scenes filmed in relatively dim lighting, those scenes will appear significantly darker than what was originally envisioned by the director.