One should presumably see the painting full sized to analyses the edges, but one can see that the figures and foreground to middle distance have sharp contrast, whereas the rest of the painting has smooth edges.

This seems like a pencil sketch he could have done before starting the painting.  

I used the Select Edges plug-in for Photoshop from Reindeer Graphics to show this as wide edges (variable 3)

A more traditional view of the edges showing more detail.

Not really sure what I can deduce from this analysis, but maybe it will become more obvious as I inspect other paintings.