-U float-number changes auto -U float-number changes auto-brightness threshold (default value is 0.01 so 1% of pixels brightened to clipping), so -U 0.0 may be useful -W option turns auto-brightness completely off -- Alex Tutubalin @LibRaw LLC reply
-U float-number changes auto-brightness threshold (default value is 0.01 so 1% of pixels brightened to clipping), so -U 0.0 may be useful
-W option turns auto-brightness completely off