See Also: CIPinLightBlendMode Members
If the CIBlendFilter.BackgroundImage pixel is more than half of the maximum brightness, that pixel is substituted for the pixel in the CIFilter.Image. Also, even if the background pixel is less than 50% brightness, it will be substituted if the image pixel is lighter than the background pixel.
This filter can be used to make an image look as if it were drawn with powder pastels.