Typically, a system level characterization of a thermal imaging device includes characterizing the objective optics, detector and readout electronics. Ultimately, the thermal imagery is converted to an 8-bit signal and presented on a display for human visual consumption. In some situations, direct characterization of the pre-sample imaging system is not possible, and measurements must be performed from analyzing the output from its display. Additionally, the performance of the display and display optics are significant contributors to the performance of the imaging system, yet they are both assumed to be ideal in many aspects. In this paper, we describe how the underlying imaging system non-uniformity is related to additional display contributions in the total system non-uniformity. This paper will be divided into three parts: the technique and considerations needed to properly measure system through its display, how we can use this information in the NVIPM performance model, and a comparison of performance from measurements at the pre-sample readout versus measurements only at the display.