Wouldn't it be a better (techie) solution to map the pixel brightness values one down the scale in dimmed mode, ie. Bright->Normal, Normal->Dim? This means you'd not loose too much contrast, only low illumination definition on the pixels illuminated as Dim.

This (I would have thought) could be done reasonably easily in the s/w.

To be honest, at night I want the driver behind to see the graphics properly...

{8^)