After owning a sony 52x3500 and turning ALL of the settings to the minimum and the set still illuminating my front room to the point that you can see your way around without turning on the light, to what the pio does which is basically not being able to see... i think that says to me that you have a set which pumps out the least luminance it possibly can...
to be able to see shadow detail in the most miniscule of light, you need some light... unfortunately, due to the fact that we use light to display images on screen, you cant get away from it showing some light. Its not that the screen is 'dark grey', its that the screen is black, but there is a faint glow which makes the mind percieve its grey.