Additionally, most cameras these days will under-expose by a pretty substantial amount. Digital darkroom software maintains a database of cameras with an entry

Additionally, most cameras these days will under-expose by a pretty substantial amount. Digital darkroom software maintains a database of cameras with an entry for how much each camera under or over-exposes (mostly under) which is applied before any of your adjustments are layered on top. Adobe's DNG spec calls this "baseline exposure". I used to always under-expose by a about a third of a stop because I reasoned that whilst I could probably recover shadow detail (even if it were noisy), once the sensor has clipped, there's nothing I can do to recover lost highlights. With modern cameras, this doesn't really make sense any more: the camera will just meter that way to begin with. It's a double-edged sword though: under-exposing will add more shadow noise. Iliah Borg (one of LibRaw's authors) has a good write-up on it: https://www.rawdigger.com/howtouse/deriving-hidden-ble-compensation https://www.rawdigger.com/howtouse/deriving-hidden-ble-compe... DXOMark also maintains a database of their own measurements of each camera, including actual ISO sensitivity for each nominal ISO sensitivity, eg: https://www.dxomark.com/Cameras/Nikon/D850---Measurements https://www.dxomark.com/Cameras/Nikon/D850---Measurements