Fast Method of Bitmap To GrayScale

public static Bitmap MakeGrayscale3(Bitmap original)
{
//create a blank bitmap the same size as original
Bitmap newBitmap = new Bitmap(original.Width, original.Height);

//get a graphics object from the new image
Graphics g = Graphics.FromImage(newBitmap);

//create the grayscale ColorMatrix
ColorMatrix colorMatrix = new ColorMatrix(
new float[][]
{
new float[] {.3f, .3f, .3f, 0, 0},
new float[] {.59f, .59f, .59f, 0, 0},
new float[] {.11f, .11f, .11f, 0, 0},
new float[] {0, 0, 0, 1, 0},
new float[] {0, 0, 0, 0, 1}
});

//create some image attributes
ImageAttributes attributes = new ImageAttributes();

//set the color matrix attribute
attributes.SetColorMatrix(colorMatrix);

//draw the original image on the new image
//using the grayscale color matrix
g.DrawImage(original, new Rectangle(0, 0, original.Width, original.Height),
0, 0, original.Width, original.Height, GraphicsUnit.Pixel, attributes);

//dispose the Graphics object
g.Dispose();
return newBitmap;
}