Optimum filters for optical correlators have been the topic of several papers in the last few years. How can there be more than one optimum? Because, different approaches optimize different functions. Most research to date has optimized some internal working function of the correlator, such as optical efficiency, or narrowness of the correlation peak. However, in the real world, there is usually some application oriented function to optimize. For example, in a tracking system, the robustness to break-lock may be the most critical function. There is a threshold in the signal to noise required for single pixel tracking. Beyond that, 'optimization power' might better be spent on increasing tolerance to aspect change, rather than increasing signal to noise. This paper will discuss the attention the filter designer must pay to bore slope error, tolerances for distortions, signal to noise, correlation width, transport delay, and other variables.