In this chapter we are going to look at a more advanced blending technique. The examples we worked through in the last chapter were quite simple. Painting in the images to hide and reveal different areas was quite easy. With some types of images we need a little help with the painting. We need more refined borders and even smoother transitions due to the complexity of the brightness differences in the images. For that kind of blending we are going to use a technique called luminance blending. What we will be doing in the samples in this chapter is using luminance, or luminosity, or brightness masks to help select the areas we want to blend and also to help us keep the transitions between areas smoother.