1. A method, comprising: electronically accessing a reference scene having a plurality of pixels; electronically accessing a testing scene having a plurality of pixels; calculating a power indicative of the intensities of the pixels of the reference scene; calculating a power indicative of the intensities of the pixels of the testing scene; and determining a difference between the power of the reference scene and the power of the testing scene; where if the difference between the powers exceeds a threshold, the difference between the powers indicates a difference between the reference scene and the testing scene; applying a plurality of non-concentric filters to the reference scene and the testing scene to calculate a plurality of filtered powers for each scene; and if a difference is detected between the reference scene and the testing scene, approximating the location of the difference by comparing the filtered powers of the reference scene and the testing scene.