Levels — Black Point, White Point, Gamma
Set black and white points manually or automatically, and adjust midtone gamma independently.
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Levels is deliberately computed in the sRGB encoded domain rather than in linear light. The slider positions in Photoshop and Lightroom have always mapped to encoded values, and users' expectations are built on that; moving the same numbers into linear light would produce a completely different look for identical settings.
Automatic mode leaves 0.1% of pixels at each end. Taking the absolute extremes would let a single hot pixel or a specular highlight decide the mapping for the entire frame.