Below is a very crude set of output for a model of the visual front end.  The model is one dimensional at present and for that I am sorry.  In addition, only X cells are modeled at this time.  On the figure below, both the input figure, plotted as pixel values from 0 to 255, and output are shown.  They each have their own y axis values next to their labels.  The output are derived from discrete instantiation of the DOG functions of Entroth-Cugell and Robson (1984) (See here for a description of DOG functions).  In the table below the figure you can manipulate certain aspects of the model and see the results immediately on the figure.  In particular you can manipulate the receptive fields by altering the standard deviations of the excitatory and the inhibitory regions.  Thus, indirectly you can manipulate the size of the receptive fields by manipulating the larger of the two standard deviation.  The model starts with cells with excitatory centers but if the excitatory region has a larger standard deviation than the inhibitory region then the cells will have inhibitory centers and the valence of the cell will be reversed.  This model currently requires that you have internet explorer 5 and a license to Office 2000 or the Excel component.  I hope to remove this limitation eventually.

You can also manipulate the input or stimulus.  This can be done manually or by equations that you can enter into an Excel table.  You can also enter this table into your Excel and play around if you click on the Excel symbol at the top of the table.  If you find something interesting let me know. 

When you are done here, there is a version of this model already done using ramp stimulus for input.