In Reinhard '05, the brightness parameter should range from -8.0 to +8.0 (see man
page for pfstmo_reinhard05). A good default value would be 0.0. But Luminance HDR sets the default brightness to -10.0, which is outside of that range. I suspect this choice is a side effect of the sRGB post-operator mapping I mentioned in a previous bug report. If the post-gamma is removed, then the pfstmo range of brightness works properly.