Could still be interesting to hear the "defense" of Andrey Tverdokhleb and Iliah Borg
who brought up this thesis about "ETTR is very harmful for colors - midpoint is the most colorful place in A900 gamut" as quoted here.
ETTR is about getting the optimal exposure from the sensors, on cameras that were calibrated to actually ETTL (from the point of view of the optimal sensor exposure). Cameras were exposing to the left essentially for two reasons
- sensors and their back office electronics implementation had a somewhat limited DR compared to what the human eye expected to see.
- engineers decided that it was better to protect from over-exposure (where data is simply lost) than fully exploit low light situations.
Sensors and their backend pipeline have improved, drastically in some cases, and that has extended the margins of DR on both sides to the point that, in some recent cameras, you just don't care.
- there are situations where ETTR is very useful (typically, Canon 5D MK II)
- there are situations where ETTR is either almost useless or harmful: the cameras that don't ETTL from the sensor point of view in the first place.
Don't forget that sensors that are very different in terms of raw capabilities are normalized for the average photographer's comfort. ISO 100 is an important reference point for photographers and should yield, give or take a bit, a similar result in all cameras. But one you've got enough DR, for example because you handle read noise better than your competitor, you can adjust gain to put it where you want it in your optimal sensor linear range.
ETTR will become more andmore useless as sensors improve in all brands. No need try to find esoteric arguments against it.