1. A method, comprising: obtaining a first image, the first image having a first focal length and a first field of view; obtaining a second image, the second image having a second focal length and a second field of view; defining a set of elements comprising a first element of the first image and a second element of the second image, wherein the first element substantially corresponds to the second element; determining a first rate of change of an image property of the first element; determining a second rate of change of the image property of the second element; and assigning the set of elements to at least one category in view of a relative difference between the first rate of change and the second rate of change.