A ugly hack would be to stop down the aperture (for example, f22 is 7 stops darker than f2.0).
http://a1ex.bitbucket.io/ML/states/600D-alt/sm70.htm - sbsDarkRelease might be related.
http://a1ex.bitbucket.io/ML/states/600D-alt/sm70.htm - sbsDarkRelease might be related.