Enblend is a tool for compositing images using a Burt & Adelson multiresolution spline. This technique tries to make the seams between the input images invisible. The basic idea is that image features should be blended across a transition zone, proportional in size to the spatial frequency of the features. For example, objects like trees and window panes have rapid changes in color. By blending these features in a narrow zone, you cannot see the seam because the eye already expects to see color changes at the edge of these features. Clouds and sky are the opposite. These features must be blended across a wide transition zone because any sudden change in color is immediately noticeable.