Application of the Cramer-Rao bound to specific information processing systems leads to theoretical performance limits, while also determining necessary conditions or design goals for these systems. The usefulness of this approach to incoherent systems is described through three example systems. These examples include single-lens, single-image, passive range estimation, range-invariant imaging, and orthogonal passive range detection systems. Each example system is a one-dimensional system for simplicity. Extensions to two-dimensional systems are straight forward.