Optical Spatial Frequency Filtering of Image Sensors ?

Of course not, I was referring to the modeled beam splitter's PSF as modified by diffraction, apologies if I wasn't clearer.  In the blog posts I linked above Frans measures end-to-end MTF for a D40 and a D7000 and compares them to the model.  Obviously the tests were carried out in controlled conditions with (I assume) tripod and best blur reducing practices.  He figures that one of the biggest contributors to discrepancies is the difficulty in achieving perfect focus