[away3d] Problem with a big texture

[Crabar]

Hello, guys!

I'm trying to use a JPEG texture with size about 6000x6000 (~19 mb) on
plane about 1000000x1000000 size.
After loading my application is in memory of more than 200 megabytes
against the usual 100. Why is this happening? JPG is unpacking into
bitmap?
Are there ways to reduce of using RAM?

Here is a code:

        public class MyPlane extends Mesh
        {
                private var TexLoader:BitmapFileMaterial;

                public function MyPlane(Xmin:Number, Xmax:Number, Zmin:Number,
Zmax:Number, Y:Number, Texture:String)
                {
                        super(null);
                        PrepareMaterial(Texture);
                        BuildFace(Xmin, Xmax, Zmin, Zmax, Y);
                        this.material = TexLoader;
                        this.bothsides = false;
                }

                private function PrepareMaterial(Texture:String):void
                {
                        TexLoader = new BitmapFileMaterial(Texture);
                }

                private function BuildFace(Xmin:Number, Xmax:Number, 
Zmin:Number,
Zmax:Number, Y:Number):void
                {
                        var FirstMainFace:Face = new Face();
                        FirstMainFace.v0 = new Vertex(Xmin, Y, Zmax);
                        FirstMainFace.v1 = new Vertex(Xmin, Y, Zmin);
                        FirstMainFace.v2 = new Vertex(Xmax, Y, Zmin);

                        FirstMainFace.uv0 = new UV(0, 1);
                        FirstMainFace.uv1 = new UV(0, 0);
                        FirstMainFace.uv2 = new UV(1, 0);

                        this.addFace(FirstMainFace);

                        var SecondMainFace:Face = new Face();
                        SecondMainFace.v0 = new Vertex(Xmax, Y, Zmin);
                        SecondMainFace.v1 = new Vertex(Xmax, Y, Zmax);
                        SecondMainFace.v2 = new Vertex(Xmin, Y, Zmax);

                        SecondMainFace.uv0 = new UV(1, 0);
                        SecondMainFace.uv1 = new UV(1, 1);
                        SecondMainFace.uv2 = new UV(0, 1);

                        this.addFace(SecondMainFace);
                }
        }
}

And I have a second little question. How to exclude object from the
influence of ZDepthFilter?

Thank you in advance.