Michael Freeman’s books on photography recommend that in any street photography you should avoid eye contact with the subject. Eye lines in photographs create interest by drawing your interest in different directions around an image, so naturally a pair of eyes looking straight back at you undermines this.
Its different in portraits of course where the eye contact engages you with the character of the subject, but as street or candid photography is rarely with the connivance of the subject this is difficult to achieve for most people will react in some way to seeing a camera pointed at them so you lose the expression that drew you to the shot in the first place.
A city like Venice is the perfect antidote to this; everyone is so used to the brandishing of lenses in all directions that they rarely consider that they might be the subject of the shot so it is easy to capture a natural expression directed straight into your camera. I was already shooting out of the side of a vaporetto when this woman boarded and stepped into shot where the combination of her haughtiness and the Rembrandt lighting created by the canopy of the vessel made her a must.