Abstract: Systems, methods and apparatus are provided through which a collimator has one or more varying physical characteristics that have the effect of varying the absorption of electromagnetic energy from a low extent of absorption at a leading edge to the same extent of absorption as the remainder of the collimator. In some embodiments, the collimator has a tapered knife-edge. The varying absorption of electromagnetic energy at different points along the collimator reduce abrupt transitions of projection of the electromagnetic energy onto an electromagnetic energy detector, thereby reducing erroneous artifacts in an image generated by the detector.