Could also be a high dynamic range operator: they do the same kind of thing to preserve contrast across large ranges of intensity. See Larson&#x27;s paper <a href="http:&#x2F;&#x2F;gaia.lbl.gov&#x2F;btech&#x2F;papers&#x2F;39882.pdf" rel="nofollow">http:&#x2F;&#x2F;gaia.lbl.gov&#x2F;btech&#x2F;papers&#x2F;39882.pdf</a> etc.