opacityLayer(string layer, integer opacity)
Sets the usual opacity of an entire layer. I.e. the layers natural opacity when not affected by opacityLayerOnEnter(). Acceptable values range 0 to 100, where 100 is fully opaque and 0 is fully transparent.
Rather than calling opacityLayer() manually, refer to the loadTiledMap() documentation as Qiso can set all of this up internally.