Uniformity (Light Falloff)

Light falloff (vignetting) and sensor nonuniformities

Light falloff (vignetting) darkens images near the corners. It can be significant with wide angle lenses. It is measured by Light Falloff (Uniformity).

Light falloff tends to be worst in wide angle lenses. It often improves when lenses are stopped down. It can be easily corrected in software. Picture Window Pro, PTLens, and several other programs have tools for removing it. Because moderate amounts of light falloff can be pictorially pleasing, it’s not always advisable to remove it completely.

Light Falloff (Uniformity) also measures other sensor nonuniformities, including stuck pixels, local sensitivity variations, spots (from dust), and noise. In Imatest Master it has a particularly rich set of displays.