Systems, apparatuses, and methods are provided for adjusting illumination slit uniformity in a lithographic apparatus. An example method can include irradiating, by a radiation source, a portion of a finger assembly with radiation. The example method can further include receiving, by a radiation detector, at least a portion of the radiation in response to the irradiating of the portion of the finger assembly. The example method can further include determining, by a processor, a change in a shape of the finger assembly based on the received radiation. The example method can further include generating, by the processor, a control signal configured to modify a position of the finger assembly based on the determined change in the shape of the finger assembly. Subsequently, the example method can include transmitting, by the processor, the control signal to a motion control system coupled to the finger assembly.