In photographic science, the Eberhard effect, named after Gustav Eberhard, is a special case of two Mackie lines when narrow areas of high and low densities (usually lines approaching within 1 mm. thickness) cause the two Mackie lines to meet which results in an increased density of this small area.[1]
Eberhard published his findings in 1912[2] or in 1926, 1931.[3]
The Eberhard effect belongs to the family of photographic edge effects.[4]