The Abbe sine condition is a condition that must be fulfilled by a lens or other optical system in order for it to produce sharp images of off-axis as well as on-axis objects. It was formulated by Ernst Abbe in the context of microscopes. The Abbe sine condition says that the sine of the object-space angle should be proportional to the sine of the image space angle Furthermore, the ratio equals the magnification of the system. In mathematical terms this is: