I didn't test out much with it, but I think you can't fade it in or anything. Maybe you can via scripting (which is way beyond me).
local Brightness=0.1
function adjust_brightness(step)
	Brightness=Brightness+step
	if Brightness>0.5 then Brightness=0.5 end
	if Brightness<-0.5 then Brightness=-0.5 end
	--- something goes here to use visionaires set brightness)
end
adjust_brightness(0.01)
adjust_brightness(-0.01)
local Brightness=100
local CurrentScene
function adjust_brightness(step)
	CurrentScene=game:getLink(VGameCurrentScene)
	Brightness=Brightness+step
	if Brightness>100 then Brightness=100 end
	if Brightness<0 then Brightness=0 end
	CurrentScene:setValue(VSceneBrightness, Brightness)
end
When calling the function the parameters have to be in percentage values for Visionaire. With this you can adjust the darkness of a scene. 100% means clearly visible as in your graphic file data, 0% results in a completely black scene. The one drawback of this scene value is that you can't brighten up the scene.