When I asked this artist in Italian yesterday evening if I could take some photos of him he answered Sì without pausing in his sketching. What attracted my attention to him in the first place was his full engagement with what he was doing.
I saw him again this evening: not far from the same spot, but setting up an easel and paints this time, and largely obscured amid the greenery of the Giardini Pubblici, protected from the foot traffic on the riva by the park's black wrought iron fence.
I didn't bother him this evening. It was after six again, when the sun seems to pick up speed in its descent and the light changes every few seconds--and it would have been a shame for me to distract him from a moment of it all.