The energy distribution itself can be used to optimally weight photons from different cross-dispersion coordinates. Plots below show surfaces where height is proportional to the sensitivity. Each profile in the cross-dispersion direction has been normalized to a unit area.
High energy is towards lower dispersion coordinate.
This model will eventually be improved through availability of better calibration data, and through ray-trace simulations which include more detailed effects. This would be properly and implicitly done in ray-trace simulations. Digitization affects are also apparent as sharp, bumpy features in the contour plots, or as streaking in the surface plots. The effective area weighting has not been included.